Adams, E.W., et al., Simulations of IAQ and comfort in multizone buildings. Indoor Air 93, 1993: pp 533-538.Strategies for IAQ improvement often impact building energy use.  The optimum strategy for IAQ requires a trade-off between improving IAQ and increasing energy use to attain it.  Modeling can be particularly effective in defining the optimal strategy for a particular site.  Modeling IAQ for building applications requires at least 4 different modeling efforts: (1) human dose-response relationship, (2) building pollutant load analysis, (3) operating cost and (4) dynamic IAQ prediction.  Effective design of control systems and operating strategies in IAQ mitigation equipment requires dynamic simulation of typical applications, including adsorption/desorption effects for pollutant species.  The coupling of energy analysis to IAQ analysis shows the energy savings available from using heat recovery combined with increased ventilation for the solution to IAQ problems.  Sample calculations show that ventilation rates must be high to limit pollutant transport between zones.  Ventilation must continue long after an event to limit discomfort.

Amara, F., P. Depecker, and F. Allard, Optibat: A real scale cell in simulated climatic environment for multizone air flow pattern in building. 13th AIVC Conf., 1992: pp 519-527.One of the main problems about air flows pattern studies remains the experimental validation of numerical codes developed for interzone air flow and pollutant diffusion prediction. A few years ago, CETHIL developed a real scale experiment made of a 88 m2 dwelling built in our laboratory hall in a controlled climatic environment. This experimental tool allows a full control of outdoor climatic conditions: air temperature, relative humidity, pressure drop can be controlled on the six faces of the cell: OPTIBAT is thus a reference tool for multizone air flow measurement techniques, and experimental data sets available for validation of numerical models. The first phase of this experimental project allowed us to determine air leakage characteristics of indoor and outdoor walls of the cell. The second element required for the validation of multizone air flow codes is the knowledge of all the interzone air flows. The vast majority of the air flow measurements made to date have involved multiple tracer gas techniques. Using the OPTIBAT facility, we have first used only one tracer gas to determine all the air flows. The present paper describes the experimental cell and gives the first results about air flows measurements using tracer gas technique. The interzone air flows are computed using 2 methods. Each method is completed by an error analysis which defines the uncertainty of each result. Both methods give the same results.

ASHRAE, An Evaluation of the Effect of CO2-Based Demand-Controlled Ventilation Strategies on Energy Use and Occupant-Source Contaminant Concentrations, . 1995, Enermodal Engineering Limited.This study examines the effectiveness of using CO2-based DCV to provide adequate IAQ with minimum energy use. A detailed building energy analysis program ENERPASS was combined with CONTAM to perform the analysis. The combined program was used to evaluate the annual heating and cooling energy consumption and CO2 and formaldehyde concentrations. The assessment was made on a mid-sized commercial building designed to comply with ASHRAE 90.1 for 4 climate zones (Chicago, Nashville, Phoenix, and Miami). 3 separate hvac systems were studied: single zone, multizone and VAV. The simulations wer made for 5 ventilation control strategies: fixed ventilation, building return air controlled to 1000 ppm and 800 ppm, floor return air controlled to 1000 ppm and each zone controlled to 1000 ppm. For single zone systems, DCV offers superior performance to fixed ventilation. At a CO2 setpoint of 1000 ppm, heating energy use is reduced by approximately 30% and average office CO2 concentrations is similar to a fixed ventilation  system. At a setpoint of 800 ppm, heating energy use is reduced by 20%, and average office CO2 levels are 50 to 90 ppm lower than with the fixed ventilation case. There is little impact on cooling energy use with the addition of CO2 controlled ventilation. CO2 control of ventilation air is recommended for single zone HVAC systems especially for zones with variable occupance (e.g. meeting rooms) in order to ensure better IAQ. Using CO2-based DCV with VAV systems offers energy savings similar to those of the single zone system. For multizone systems. the reduction in heating is similar in absolute terms but, because of the larger heating load, is smaller in percentage terms (5 to 12%). For both systems, the average CO2 concentraiton with a control setting of 1000 ppm is 70 to 150 ppm higher than with the fixed ventilation case. Lowering the setting to 800 ppm results in lower CO2 levels than the fixed ventilation case and keeps the maximum concentrations below 1000 ppm for all zones. CO2 controlled ventilation is recommended in multizone and VAV systems for most climates to save heating energy. In warm climates, however, the heating savings are small and probably do not justify a CO2 based system. Providing additional sensors in the return duct of each floor had little impact on energy use and IAQ. Installing sensors in each zone increases energy use slightly and ensures that the concentration in each zone stays below 1000 ppm. This would, of course, be a more expensive control option. Central control set to 800 ppm offers similar performance to sensors in each zone, but at a much lower installed cost. Demand controlled ventilation did not control the concentration of formaldehyde as well as the fixed ventilation case for any of the control strategies studied. CO2 control of ventilation should include a morning purge cycle where non-occupant generation of pollutants is of concern.
Also ASHRAE paper by Stephen Carpenter.

Axley, J.W., Indoor Air Quality Modeling Phase II Report, . 1987, National Institute of Standards and Technology: Gaithersburg.This interim report presents the results of Phase II of the NBS General Indoor Air Pollution Concentration Model Project. It describes the theoretical basis of a general-purpose nonreactive contaminant dispersal analysis model for buildings, the computational implementation of a portion of this model in the program CONTAM86, and examples of the application of this model to practical problems of contaminant dispersal analysis. Presently the model is being extended to handle problems of reactive contaminant dispersal analysis and full computational implementation of all portions of the model is being completed.

The contaminant dispersal analysis model is based upon the idealization of building airflow systems as an assemblage of flow elements connected to discrete system nodes corresponding to well-mixed air zones within the building and its HVAC system. Equations governing the airflow processes in the building (e.g., infiltrations, exfiltration, HVAC system flow, and zone-to-zone flow) and equations governing the contaminant dispersal due to this flow, accounting for contaminant generation or removal, are formulated by assembling element equations so that the fundamental requirement of conservation of mass is satisfied in each zone. The character and solution of the resulting equations is discussed and steady and dynamic solution methods outlined.

Axley, J.W., Progress Toward A General Analytical Method for Predicting Indoor Air Pollution in Buildings - Indoor Air Quality Modeling Phase III Report, . 1988, National Institute of Standards and Technology: Gaithersburg.

Axley, J.W. and R. Grot, The Coupled Airflow and Thermal Analysis Problem in Building Airflow System Simulation. ASHRAE Transactions, 1989. Vol. 95.2: pp 621-628.The IAQ and V group at NIST has developed a method of building airflow analysis, based upon element assembly techniques, that has been successfully applied to the determination of the macroscopic characteristics of infiltration, exfiltration, and interzonal airflows in complex building airflow systems driven by wind pressures, buoyant forces, and the building HVAC system. This analytical method was formulated to be compatible with a discrete thermal analysis method, also based on element assemblyn techniques and developed earlier, which may be applied to problems of building thermal analysis. This paper will review the theoretical bases of these two related methods and present a theoretical framework to solve the coupled airflow and thermal analysis problem in building airfl,ow system simulation. Formulation of the coupled airflow-thermal analysis problem will be presented and numerical methods for the solution of this problem will be outlined.

Axley, J.W., Multi-zone dispersal analysis by element assembly. Building and Environment, 1989. Vol. 24(2): pp 113-130.general theoretical discussion of multizone modeling which includes consideration of non well-mixed zones (2 node convection diffusion element to model duct flow)

Axley, J.W., Element Assembly Techniques and Indoor Air Quality Analysis. 1990: pp 115-120.Element assembly techniques have been applied to develop methods to model a) airborne contaminant dispersal, b) airflow, and c) heaat transfer in complex multi-zone building systems. Individually, these methods allow an integrated consideration of the building envelope, construction, and mechanical system interaction, are computationally non-demanding, and can be employed to model whole building systems of arbitrary complexity. As a group, these methods are, in principle, computationally compatible and are presently being integrated to provide comprehensive IAQ analysis capabilities. This paper will present an outline of the theory underlying these methods and describe the US NIST families of programs that implement them.

Axley, J.W., Adsorption Modeling for Macroscopic Contaminant Disperal Analysis. 1990.Two families of macroscopic adsorption models are formulated, based on fundamental principles of adsorption sciene and technology, that may be used for macroscopic contaminant dispersal analysis. The first family of adsorption models - the Equilibrium Adsorption Models - are based upon the simple requirement of equilibrium between adsorbent and room air. The second family - the Boundary Layer Diffusion Controlled Adsorption Models - add to the equilibrium requirement a boundary layer for diffusion of the adsorbate from the room air to the adsorbent surface. Two members of each of these families are explicityly discussed, one based on the linear adsorption isotherm model and the other on the Langmuir model. The linear variants of each family are applied to model the adsorption dynamics of formaldehyde in gypsum wallboard and compared to measured data.; N;

Axley, J.W. and D. Lorenzetti, Sorption Transport Models for Indoor Air Quality Analysis. ASTM STP 1205, 1992.Sorption filtration is presently being investigated as one means to control the quality of air in buildings, yet methods to integrate models of sorption filtration devices with multizone indoor air quality procedures - to enable rational design of these devices - have not appeared. This paper reviews the theoretical bases of sorption models recently developed for multizone contaminant dispersal analysis and presents new work to extend these models to the problem of sorption filtration modeling. Four generic families of models are presented that account for (a) the equilibrium limits of reversible sorption processes with or without (b) boundary layer diffusion transport at the adsorbent surface and (c) diffusion transport within the adsorbent proper, and, for filtration devices, (d) convection-diffusion transport within the filtration medium. All models are formulated as mass transport elements that may be directly assembled with existing elements to model contaminant dispersal in multizone building/HVAC systems of arbitrary complexity. A comparison of the model families is made, criteria are presented to aide in the selection of the model family to use, and results of first applications of these models are presented that provide some validation of the theory.

Axley, J.W. Macroscopic formulation and solution of ventilation design problems. in 18th AIVC Conference. 1997.

Axley, J.W., Passive Ventilation for Residential Air Quality Control. ASHRAE Transactions, 1999. Vol. 105(2).Discussion of passive ventilation systems, components, operation, and design. Presentation of design methodology utilizing loop equations. Theoretical background is provided along with simple example of design method.

Axley, J.W. Design and Simulation of Natural Ventilation Systems Using Loop Equations. in Healthy Buildings 2000. 2000. Espoo, Findland.

Bassett, M.R. Passive Ventilators in New Zealand Homes: Part 1 Numerical Studies and Part 2 Experimental Trials. in 15th AIVC Conference - The Role of Ventilation. 1994. Buxton, Great Britain: AIVC.This paper is part one of a study of passive ventilation options for NZ homes. It explores numerically a range of ventilator sizes and locations in typocal homes modelled in the climate of major New Zealand cities. Part two offers experimental verification of the ventilator performance data calculated here. A numerical multizone airflow model was used to calculate the effect of adding stack and window type passive vents to huses of a range of airtightness levels. Wind pressure was found to be the dominant driving force of airflows delivered by window-mounted passive ventilators. Stack ventilators reduced the strong dependence of window ventilator airflows on wind speed when both types were preesent in a building, but when the ventilation system made small changes to the overall airtightness of the house, the role of the stack ventilator was less obvious. A simple linear function linking ventilator opening area with average added ventilation rates is presented for wall-mounted passive ventilator systems in NZ buildings.

Berne, P. Prediction of the concentration decay in a ventilated enclosure by the multizone model. in Roomvent 94. 1994.

Blomsterberg, A., Ventilation and Airtightness in Energy Balance. 10th AIVC Conf., 1989: pp 305-324.The air exfiltration part of ventilation is often difficult to determine and its part of the energy balance is therefore usually determined as a remainder or given a constant value. This paper examines ventilation systems in six different modern houses. The constant concentration tracer gas technique tended to underestimate the total ventilation. A simplified theoretical one-zone model made accurate estimations of the air exfiltration. For detailed information on air flows a multi-zone network model was useful. Different levels of airtightness should be required depending upon the ventilation system. It is recommended to couple predictions with tracer gas measurements. Determining the energy balance, eg, using a constant air change rate for the mechanical and/or natural ventilation is in most cases inaccurate, unless the house is very tight.

Blomsterberg, A., Ventilation Control within Exhaust Fan Ventilated Houses. 12th AIVC Conf., 1991: pp 285-305.Modern one-family houses in Scandinavia are often ventilated by an exhaust fan.  Most of the outdoor air probably enters through whatever cracks and openings there are and only a small part enters through the supply vents in many of these houses.  The overall supply of outdoor air might be adequate, but some rooms often do not get enough of outdoor air. The constant concentration tracer gas technique was used to examine the supply of outdoor air.  Fan pressurization combined with infrared photography were employed to characterize the air leakage of the building.  A multizone network model was used to further e aluate the measurements. A reasonable level of outdoor air, upstairs in an airtight two-storey house, can be ensured by locating the supply venta upstairs close to the floor.  If that is not possible additional exhaust vents can be installed.  If more that 3/4 of the outdoor air is to enter throught the supply vents, then the airtightness should be better than 1.0 ach at 50 Pa.  The performance of an exhaust fan system is very much dependent upon the overall airtightness (including open supply vents) and the distribution of the airtightness of the building.

Blomsterberg, A. and M. Wall, The energy impact of ventilation and air infiltration in an atrium. 14th AIVC Conf., 1993. Vol. 1.Many modern office and residential buildings in Sweden include an atrium. The atria are often mechanically ventilated and sometimes they are heated. Very little is known about the ventilation and air infiltration in built atria. These issues were examined in an apartment building with a nonheated and mechanically ventilated atrium, built in 1986 in Sweden. The ventilation of the atrium is coupled to the apartments. The pper examines the ventilation, air infiltration, airtightness and the energy impact of an atrium. Fan pressurization was employed to characterize the air leakage of the atrium and the apartments. The energy use and temperatures in the atrium and in the apartments were monitored continuously for a year. A multizone network model was used to further evaluate the ventilation and the air infiltration. The energy balance was estimated using a dynamic simulation model. The roof of the tested atrium is very leaky and therefore the exfiltration is large. The energy use for space heating of the tested apartments can be reduced if the atrium and the apartments are made tighter. The knowledge concerning the real airtightness and ventilation of atria and surrounding buidings is insufficient. There are also many ideas as to how to ventilate an atrium.

Borchiellini, R., M. Cali, and M. Torchio, Experimental Evaluation of COMIS Results for Ventilation of a Detached House. 1995.The comparation of the measured air flow in a detached house built by ITALGAS with the results of a simulation model are given in this paper. The detached house has been built mainly for experimental purposes and therefore allows very detailed measurements of the internal and outside microclimate (e.g. wind velocity, air temperature, humidity, etc.). Furthermore, the air permeability of the house has been characterised by means of the pressurisation technique. The ventilation measurements have been carried out using the tracer gas technique (decay method with 2 gases: SF6 and N2O). A mobile, multizone, multitracer apparatus designed and built at the Dipartimento di Energetica of the Politecnico di Torino has been used. The measured data has been analysed using an inverse problem technique in order to calculate the time histories of the air flow rates during the measurement period and their uncertainties. The building envelope air leakage coefficients and the meteorological data has been used in COMIS to obtain the simulated air flow rates. The comparison with the measured airflow allows one to define the application limits of the here studied model.; ;

Chung, K.-C., The evaluation of total IAQ in a multizone model of a building. Indoor Built Environment, 1996. Vol. 5: pp 291-302.

Clarke, J.A. and J. Hensen, An Approach to the Simulation of Coupled Heat and Mass Flows in Buildings. Proceedings of the 11th AIVC Conference, 1990. Vol. 1.This paper describes the techniques used within the ESP system to represent and solve the heat and mass conservation equations relating to combined building and plant systems. In particular, it describes the equation-sets used to represent inter-zonal (building) and inter-component(plant) fluid flow and the method used for the integration of the nonlinear heat and mass flow equations. By means of a case study, the application in a real design context is demonstrated.

Clarke, J.A., W.M. Dempster, and C. Negrao, The implementation of a CFD algorithm within the ESP-r system. Building Simulation 95, 1995. Vol. x: pp 166-175.This paper describes the implementation of a cfd algorithm within the ESP-r building energy modeling system. While the implementation is specific to ESP-r, the conflation approach is general anc could be applied to other building performance appraisal programs. The paper also presents an example application to indicate the potential effects of the enhanced modelling resolution and some of the new issues to emerge.

Clarke, J.A., J.L.M. Hensen, and C.O.R. Negrao, Predicting indoor air flow by combining network approach, CFD and thermal simulation. 16th AIVC Conf., 1995. Vol. x: pp 145-174.This paper describes a method which aims to generatean overall view of multizone building air flow by integrating methods for bulk air flow analysis, air flow field analysis, and thermal analysis. This has been achieved by implementing a CFD approach within the ESP-r buiding energy simulation environment which already incorporated a nodal air flow network approach. The current state of the method is demonstrated by a case study. The main conclusion form this is that the integrated method is very promising . Other preliminary conclusions concern the difficulty of finding suitable boundary conditions and numerical values for input parameters.

Creuzevault, D., et al., An Indoor Air Quality Prediction Model. Indoor Air 90, 1990. Vol. 4: pp 165-170.The analysis, use and validation of a model has been briefly presented here, it has a broad scope since it covers different professions (engineers, doctors) and skills. Modelling should afford a better analysis and understanding of the findings of the socio-cultural analysis (simulation using representative cases). Parametrical simulation studies will allow cost specifications to be proposed with respect to services and equipment meeting the desired health an safety criteria.

de Gids, W.F. and J.C. Phaff, Recirculation of Air in Dwellings. 9th AIVC Conf., 1988: pp 301-310.The Dutch Std NEN 1087 "Ventilation of dwellings". Requirements, is at this moment under review. A statement is made that outside air is required as fresh air for bedrooms. Bathroom, kitchen, W.C. and living room are allowed to be ventilated with air from other rooms. During the last years air heating systems became more popular. These systems have n its most simple form recirculation of air from the LR the the bedrooms. The requirement of frest outside air for bedrooms can only be reached with these systems when selective recirculation takes place. During the reviewing process of the std, TNO has carried out some studies to investigate the differences in concentrations of contaminants in dwellings due to different ventialtion and heating systems. Measurements and calculations have been made in a lot of conditions to reconsider the requirement of pure outside air for bedrooms. In this investigation the following aspects were studied;,

Dols, W.S., G.N. Walton, and K. Denton, CONTAMW 1.0 User Manual, . 2000, National Institute of Standards and Technology: Gaithersburg.This manual describes the computer program CONTAMW developed by NIST. CONTAMW is a multizone indoor air quality and ventilation analysis program designed to help you determine: airflows - infiltration, exfiltration, and room-to-room airflows in building systems driven by mechanical means, wind pressures acting on the exterior of the building, and buoyancy effects induced by temperature differences between the building and the outside; contaminant concentrations - the dispersal of airborne contaminants transported by these airflows and transformed by a variety of processes including chemical and radio-chemical transformation, adsorption and desorption to building materials, filtration, and deposition to building surfaces; and/or personal exposure - the prediction of exposure of building occupants to airborne contaminants for eventual risk assessment.
CONTAMW can be useful in a variety of applications. Its ability to calculate building airflows is useful for assessing the adequacy of ventilation rates in a building, to determine the variation in ventilation rates over time, to determine the distribution of ventilation air within a building, and to estimate the impact of envelope air-tightening efforts on infiltration rates. The prediction of contaminant concentrations can be used to determine the indoor air quality performance of buildings before they are constructed and occupied, to investigate the impacts of various design decisions related to ventilation system design and building material selection, to evaluate indoor air quality control technologies, and to assess the indoor air quality performance of existing buildings. Predicted contaminant concentrations can also be used to estimate personal exposure based on occupancy patterns.

Dorer, V., et al., Evaluation of COMERL with the LESO Dataset, . 1992, EMPA.

Dorer, V. and J.-M. Furbringer. Comparison of multizone air flow measurements and simulations of the LESO building including sensitivity analysis. in 14th AIVC Conference. 1993.

Dorer, V. and A. Weber, Simulation of Passive Cooling and Natural Facade Driven Ventilation. 15th AIVC Conf., 1994.IN many design cases, energy as well as ocupant comfort are the relevant ccriteria which are studied using computer simulation programs. Comfort evaluations cover air quality, thermal, visual and acoustical domfort. For all these individual aspects, specific simulation programs are available today, but very few programs allow for the integrated evaluation of several or all relevant parameters. The more, heat transport, ventilation as well as lighting are physically coupled and therefore must be integrally modelled in the simulation process. This paper gives a short description of the concept used for the coupling of the air flow simulation code COMVEN with the building and systems simulation code TRNSYS. Then, 2 application examples typical for a building design study situation are presented. The first example shows a multi-story biulding which is passively cooled at night-time due to natural stack airflow. The influence of the operation of the openings on the maximum room temperatures is discussed for a hot summer period case. The facade of the ubilding of example 1 shall be retrofitted with a glazed outer facade. In example 2, the natural ventilation of this building is studied. Ventilation is provided by naturally driven shaft ventilatoin through the facade spaces. Control strategies for the openings and the blinds are discussed in respect to overheating risk and minimum air flow rates.

Edwards, R. and C. Irwin, An overview of methodologies for the assessment of the performance of domestic ventilaton systems. 15th AIVC Conf., 1994. Vol. 1.As levels of thermal insulation used in dwellings increase, so the significance of the choice of ventilation strategy increases, in terms of range of factors such as energy consumption, pollutant control, and running and maintenance costs. It is generally desirable to be able to make use of computer based performance assessment tools. This paper briefly discusses the key dwelling performance factors which are influenced by choice of ventilaton strategy, and compares a cross section of assessment tools with differing capabilities. It is found that the degree of integration of performance factor assessment is poor, particularly with regard to financial implications.

Emmerich, S.J., A.K. Persily, and D.A. VanBronkhorst, A Workplan to Analyze the Energy Impacts of Envelope Airtightness in Office Buildings, . 1995, National Institute of Standards and Technology.The purpose of this study was to estimate the energy use in commercial buildings due to infiltration and ventilation airflows and to investigate the potential for energy savings that could be realized by envelope tightening efforts. A set of 25 buildings was used as a representative sample of the U.S. commercial building stock as of 1995. Buildings were located in cities throughout the U.S. so that a representative sample of climates was also taken into account. Leakage characteristics were assigned to each building based on limited envelope leakage data that exist for U.S. office buildings.

Emmerich, S.J. and A.K. Persily, Multizone Modeling of Three Residential Indoor Air Quality Control Options, . 1996, National Institute of Standards and Technology.The National Institute of Standards and Technology (NIST) performed a preliminary study of the use of central forced-air heating and cooling system modifications to control indoor air quality (IAQ) in residential buildings. The objective of this effort was to provide insight into the use of state-of-the-art multizone airflow and IAQ models to evaluate such modifications, the potential of these modifications to mitigate residential IAQ problems, the pollutant sources they are most likely to impact, and their potential limitations. This study was not intended to determine definitively whether the IAQ control options studied are reliable and cost-effective. Another important objective of the project was to identify issues related to the use of multizone IAQ models and to identify areas for follow-up work.

This report summarizes the three phases of this effort, each of which consisted of three main tasks. The Phase I tasks included conducting a literature review, developing a plan for computer analysis, and holding a workshop to discuss the plan. The Phase II.A tasks included baseline simulations of contaminant levels without indoor air quality (IAQ) controls, design of the IAQ control retrofits, and preliminary simulations of contaminant levels with the IAQ control retrofits. The Phase II.B tasks included computer simulations of contaminant levels with IAQ control retrofits, evaluation of the effectiveness of the IAQ control retrofits, and development of recommendations for future research. This report is a consolidation of the three previous reports on the project: Emmerich and Persily 1994 on Phase I, Emmerich and Persily 1995a on Phase II.A, and Emmerich and Persily 1995b on Phase II.B.

The multizone airflow and pollutant transport program CONTAM93 was used to simulate the pollutant concentrations due to a variety of sources in eight buildings with typical HVAC systems under different weather conditions. Three indoor air quality control technologies were  
incorporated into the house models to determine their effectiveness in controlling the modeled pollutant sources. The technologies include the following: electrostatic particulate filtration, heat recovery ventilation, and an outdoor air intake damper on the forced-air system return.

Simulation results indicate that the system modifications reduced pollutant concentrations in the houses for some cases. However, the heat recovery ventilator and outdoor air intake damper increased pollutant concentrations in certain situations involving a combination of weak indoor sources, high outdoor concentrations, and indoor pollutant removal mechanisms. In cases where the IAQ controls reduced pollutant concentrations, they led to larger relative reductions in the tight houses than in the houses with typical levels of airtightness, though the typical houses still had lower post-control concentrations. The controls had the largest impact on concentrations of a non-decaying pollutant from a constant source. Limited system run-time under mild weather was identified as a limitation of IAQ controls that operate in conjunction with forced-air systems.

Emmerich, S.J. and A.K. Persily. Energy Impacts of Infiltration and Ventilation in U.S. Office Buildings Using Multizone Airflow Simulation. in IAQ and Energy 98. 1998. New Orleans, Louisiana: ASHRAE.

Emmerich, S.J. and S.J. Nabinger, Measurement and Simulation of the IAQ Impact of Particle Air Cleaners in a Single-Zone Building, . 2000, National Institute of Standards and Technology.This report describes the initial phase of an effort to evaluate the ability of multizone airflow and pollutant transport models to predict the impact of residential IAQ control technologies. Measurements of the performance of several particulate air cleaning devices and related particle transport parameters were performed in a one-room test house. These measurements were used to calculate building air change rates, particle deposition rates and penetration factors, and air cleaner removal efficiencies. Two separate 24 h tests were performed with two of the tested air cleaners, and the measured air change rates and particle concentrations were compared to predicted values obtained with the CONTAM model. For both tests, simulated 24 h average air change rates were within 5 % of measured air change rates and simulated 24 h average particle concentrations were within 30 % of measurements for all particle sizes. Simulations were also performed to predict the impact of the air cleaners compared to a typical furnace filter.

Fang, J.B. and A.K. Persily, Airflow and Radon Transport Modeling in Four Large Buildings. ASHRAE Transactions, 1995. Vol. 101(1).Computer simulations of multizone airflow and contaminant transport were performed in four large buildings using the program CONTAM88. This paper describes the physical characteristics of the buildings and their idealizations as multizone building airflow systems. These buildings include a 12-story multifamily residential building, a 5-story mechanically ventilated office building with an atrium, a 7-story mechanically ventilated office building with an underground parking garage, and a one-story school building. The air change rates and interzonal airflows of these buildings are predicted for a range of wind speeds, indoor-outdoor temperature differences, and percentages of outdoor air intake in the supply air. Simulations of radon transport were also performed in the buildings to investigate the effects of indoor-outdoor temperature difference and wind speed on indoor radon concentrations.

Fang, J.B. and A.K. Persily, Computer Simulations of Airflow and Radon Transport in Four Large Buildings, . 1995, National Institute of Standards and Technology.Computer simulations of airflow and radon transport in four large buildings were performed using CONTAM. The buildings modeled included a twelve-story multi-family residential building, a five-story mechanically-ventilated office building with an atrium, a seven-story mechanically-ventilated office building with an underground parking garage, and a one-story mechanically-ventilated school building. Interzone airflow rates and radon concentrations were predicted in these buildings as a function of wind speed and direction, indoor-outdoor temperature difference, and ventilation system operation. Ventilation system factors that were studied included the operation of exhaust fans in the apartment building and variations in the percent outdoor air intake in the office buildings. Simulations in the office buildings were also made with the ventilation systems off and with variations in the balance of the supply and return airflow rates.

Farrington, F., Air distribution and contaminant mobility modeling throughout commercial passenger aircraft. 1996.

Ferriera, M.J. Analysis of Smoke Control System Design Using a Computer-based Airflow Analysis. in Pacific Rim Conference and Second International Conference on Performance-Based Codes and Fire Safety Design Methods. 1998. Maui, Hawaii.

Feustel, H.E., Mathematical Modelling of Infiltration and Ventilation. 10th AIVC Conf., 1989: pp 157-179.It is particularly important to be aware of the ir flow pattern in a building when determining indoor air quality problems or calculating space conditioning loads for energy consumption. Correct sizing of space conditioning equipment is also dependent upon accurate air flow information. A number of infiltration models have been developed to calculate infiltration-related energy losses and the resulting air flow distribution in both, single-zone and multi-zone buildings. International infiltration research has been conducted since the early twenties - infiltration modeling, however, is a relatively new task. Most of the modeling effort has taken place during the last 15 years. This paper gives an overview of the development of infiltration models.

Feustel, H.E., et al., The COMIS Infiltration Model. 10th AIVC Conf., 1989: pp 233-251.The COMIS workshop, using a multi-national, is planning to develop a reliable, smooth running multizone infiltration model on a modular base. This model not only takes crack flow into account but also covers flow through large openings, single-sided ventilation, cross ventilation and HVAC systems. The model contains a large number of modules which are peripheral to a steering program. COMIS can also be used as a basis for future expansion in order to increase the ability to simulate buildings. Small task groups were formed to work on particular problems in developing the modules. Each COMIS team member works on several task groups.

Feustel, H.E., The COMIS Air Flow Model a Tool for Multizone Applications. Indoor Air 90, 1990. Vol. 4.It is particularly important to be aware of the air flow pattern in a building when determining IAQ problems or calculating space conditioning loads for energy consumption. A number of infiltratin models have been developed to calculate infiltration-related energy losses and the resulting air flow distribution in both, single-zone and multizone buildings. The COMIS workshop, using a multi-national team, developed a multizone infiltration model on a modular basis. This  model not only takes crack flow into account but also covers flow through large openings, single-sided ventilation, cross ventilation and HVAC systems. COMIS can also be used as a basis for future expansion in order to increase the ability to simulate buildings. This paper gives an overview of the workshop and the developed model.

Feustel, H.E. and J. Dieris, A Survey of Air Flow Models for Multizone Structures. 1991.Air flow models are used to simulate the rates of inc oming and outgoing air flows for a building with known leakage under given weather and shielding conditions. Additional information about the flow paths and air-mass flows inside the building can only be made by using multizone air flow models, a literature review was performed in 1984. A second literature review and a questionnaire survey performed in 1989, revealed the existence of 50 multizone air flow models, all developed since 1966, two of which are still under development. All these programs use similar flow equations for crack flow, but differ in the versatility to describ4e the full range of flow phenomena and the algorithm provided for solving the set of nonlinear equations. This literature review has found that newer models are able to describe and simulate the ventilation systems and interrelation of mechanical and natural ventilation.; ;

Field, A.J., W.J. Batty, and S.D. Probert, A Multizone model to facilitate predicting natural ventilation through buildings. 12th AIVC Conf., 1991. Vol. 1: pp 139-159.A mathematical model ahs been developed which will facilitate the prediction of infiltration rates withing multizone buildings. The aim was to cater for: (i) significantly different temperatures in different parts of the building; (ii) flow paths at any height, including vertical connections between zones; and (iii) flow paths extending over large vertical distances. These aims led to the requirement in the associated computer program that the variation of pressure with height be accounted for independently within each zone of the building. In order to achieve these aims, the flows between zones were modelled by considering pressure differences and flow resistances. The neutral pressure level approach was found to introduce unnecessary complications. If the pressure in each zone varies with height, and at a rate which depends ohn the zone temperature, it is necessary to determine the pressure in each zone at a reference height. The floor level of each zone was chosen as the reference height. The total building pressures are solved simultaneously to give these reference pressures. Predictions obtained from the developed computer program have been compared with analytical solutions for simple systems as well as experimental data.

Fischer, R.D. and R.A. Cudnik, The House-II Computer Model for Dynamic and Seasonal Performance Simulation of Central Forced-air Systems in Multi-zone Residences. ASHRAE Transactions, 1993. Vol. 99, Pt 1.This is the first of a series of papers on the HOUSE-II computer model developed in Phase IV of ASHRAE SP 43 for dynamic and seasonal performance simulation of a central forced-air space conditioning system in a multizone residence. This paper reviews our prior work with the single-zone model, discusses the need for a multi-zone version of the model, describes the conversion to multi-zone capability, and describes modeling capability and the present status of the HOUSE-II multi-zone model.

Furbinger, J.M. and R. Borchiellini, Technique of Sensitivity Analysis Applied to an air Infiltration Multizone Model. ASHRAE Transactions, 1993. Vol. 99 Pt 2.This paper presents the results of simulations of test houses using a nodal simulation infiltration code. The two detached houses are 3 level family houses consisting of a basement where technical rooms and instruments are placed; the first floor, which is the test level; and a loft. The paper also  presents the fractional factorial experimental design used to estimate parameter and interactive effect coefficients; by varying input parameters, such as airtightness and wind speed, for example, it is possible to make obvious which are the critical parameters and what level of confidence is required for input parameters to guarantee a given confidence in the output. The capability of the sensitivity analysis and the mean age-of-air to serve as tools for air quality evaluation is discussed. Comments on parameter interaction, as well as recommendations for a more general sensitivity study including several types of buildings, are also provided.

Furbringer, J.-M., et al. Air flow simulation of the LESO building including a comparison with measurements and a sensitivity analysis. in Indoor Air 93. 1993.

Furbringer, J.-M. Comaprison of the accuracy of detailed and simple model of air infiltration. in 15th AIVC Conference. 1994.

Furtaw, E.J., et al., Modeling Indoor Air Concentrations Near Emission Sources in Imperfectly Mixed Rooms. Eng. Sol. to IAQ Prob., 1995.Assessments of exposure to indoor air pollutants usually employ well-mixed models which assume homogeneous concentrations throughout a building or room. However, practical experience and experimental data indicate that concentrations are not uniform in rooms containing point sources of emissions; concentrations tend to be greater inclose proximity to the source than they are further from it. This phenomenon could account for the observation that personal air monitors frequently yield higher concentrations than nearby microenvironmental monitors. In this project, we systematically studied the concentraitons of a tracer gas at various distances from its emission source in a controlled-environment  room-size chamber, under a variety of ventilation conditions. Measured concentrations in the proximity of the source deviated significantly above the predictions of a conventional well-mixed single-compartment mass balance model. The deviation was found to be a function of distance from the source and ventilation rate. At typical room ventilation rates, the average concentraiton at arm's length (~0.4m) from the source exceeds theoretical by a ratio of about 2:1. However, this ratio is not constant; the monitored concentraiton appears to randomly vary from near the theoretical value to several times above it. Concentration data were fitted to a two-compartment model with the source located in a small virtual compartment within the room compartment. These two compartments are linked with a stochastic air transfer rate parameter. The resulting model provides a more realistic simulation of exposure concentrations than does the well-mixed model for assessment of exposure to emissions from active sources. Parameter values are presented for using the enhanced model in a variety of typical situations.

Godish, T. and J. Spengler, Relationship between ventilation and indoor air quality: a review. indoor air, 1996. Vol. 6: pp 135-145.

Grimsrud, D.T., et al. Radon entry into large buildings and energy conservation. in Indoor Air 96. 1996.

Grosso, M., D. Marino, and E. Parisi. A wind pressure distribution calculation program for multizone airflow models. in Building Simulation '95. 1995. Madison, WI: International Building Performance Simulation Association...
In order to obtain a more detailed evaluation, taking the Cp distribution on the envelope of buildings into account, a numerical model (CPCALC+) based on a parametrical analysis of wind tunnel test results was developed at LBL for the COMIS multizone airflow calculation program and upgraded with the CEC-DGXII PASCOOL program. CPCALC+ calculates Cp values at any position of a surface element on the envelope of a rectangular shaped building with flat or tilted roof for given conditions of terrain roughness, density of surrounding buildings, shape ratios,m and wind direction. This paper describe3s the parametrical approach used to analyse the reference Cp data as well as the algorithms included in the calculation model. The variation of Cp with respect to reference boundary condition was analysed in relation to several parameters: wind velocity profile exponent, plan area aspect ratios, wind incidence angle, roof tilt angle, facade element positioning co-=ordinates. Some of the relevant cuve-fitting function are shown. A flowchart of the program is also presented.

Grot, R.A. and J.A. Axley, Structure of Models for the prediction of air flow and contaminant dispersal in buildings. Proceedings of the 11th AIVC Conference, 1990: pp 223-266.This paper treats the structure of models for predicting interzonal airflow and contaminant dispersal in buildings. It will discuss the mathematical structure of such models, the use of modern data structures, the application of structured program techniques and the use of object-oriented structures for the development of user interfaces and building description processes. Two computer models developed at NIST will be used as examples of how these techniques can be applied to air flow analysis and contaminant dispersal: NBSAVIS - a building description processor for multizone buildings, and CONTAM88 - an interzonal airflow and contaminant disperal analysis program. NBSAVIS treats the building as a collection of physical objects which have flow and leakage characteristics and creates a building idealization (flow paths, zones and contaminant source data) from the physical description building. It will be demonstrated that with the proper data structure, general interfaces which are both user-friendly and physically correct can be developed. CONTAM88 combines previously developed interzonal airflow and contaminant dispersal analysis programs AIRMOV, CONTAM86, AND CONTAM87 into one model which includes such features as contaminant reactions, pressure induced contaminant sources for modeling radon entry and plateout and disposition of contaminants onto surfaces. An example is presented on the use of these programs for airflow and contaminant dispersal analysis in a large apartment building.

Haghighat, F. and J. Rao, Computer-aided building ventilation system design - a system-theoretic approach. Energy and Buildings, 1991. Vol. 17: pp 147-155.An understanding of the pattern of airflow is an important element in the design of ventilation systems. The airflows are caused by wind effect, stack effect and mechanical ventilation systems. Several models have been developed to analyse the airflow in buildings. So far, the focus has been on the modelling process. In this paper, the modelling and analysis of building ventilation sytems using a system-theoretic procedure are presented. The emphasis is on presenting a theoretic derivation of nodal-governing equations for building airflow systems and obtaining efficient procedures for automatic formulation of the system equations. This approach is based on matrix algebra, therefore is easy to implement on a computer.

Haghighat, F. and A. Megri, A comprehensive validation of two airflow models - COMIS and CONTAM. Indoor Air, 1996. Vol. 6: pp 278-288.

Hamlin, T. and K. Cooper, The potential for residential demand controlled ventilation. 12th AIVC Conf., 1991: pp 235-243.

Heikkinen, J. and M.-L. Pallari. Improvement of Domestic Ventilation Systems. in 15th AIVC Conference - The Role of Ventilation. 1994. Buxton, Great Britain: AIVC.The aim of the study was to identify methods for the renovation of ventilation systems in domestic buildings which are 3 - 8 eight storeys high. Three typical buildings were selected and the problems in ventilation were examined. The designers made their proposals for repairs and the research team analyzed the solutions and made improvements. The special problems compared with new buildings included less aritight building envelopes and leakages in existing ventilation ducts.
An analysis was performed, using a multi-zone airflow model, for the whole year and therefore the ventilation heat loss could be found in each case. As anticipated, the airflow rate of passive stack ventilation was too high in winter an too low in summer, bu the system can be improved with demand-controlled ventilation instead of time control. The installation of heat recovery sytem requires improved sealing of the building envelope to minimuze cross ventilation. The proposed systems will be tested and followed up later in experimental buildings.

Heiselberg, P., Concentration distribution in the centre plane of a ventilated room under isothermal conditions. Indoor Air, 1993. Vol. 3: pp 34-40.This paper presents a series of full-scale measurements of the concentration distribution in the centre plane of a room with isothermal mixing ventilation.
Vertical profiles of the concentration in the middle of the room have been measured under different conditions. With the contamination source in the middle of the room the vertical profiles were changed radically with an increase of the air change rate from n=1.5h-1 to n=6h-1 due to a change in the flow structure in the room. With a constant air change rate, the location of the contamination source in the room showed a great influence on the vertical profile. A high velocity around the contamination source resulted in a uniform contaninant distribution in the room, while a low velocity resulted in considerable differences.
Contours of concentraiton in the centre plane of the room have been measured using different contaminant densities. The densities were low, neutral and high in relation to the density of air. The results showed that the contaminant distribution in the room with the chosen flow conditions depended strongly on the contaminant desntiy, and that the high density case gave the highest concentraitons in the occupied zone.
Andy has journal.

Hensen, J.L.M., On the thermal interaction of building structure and heating and ventilating system. 1991.In this dissertation, developments in the field of building performance evaluation tools are described. The subject of these tools is the thermal interaction of building structure and heating and ventilating system. The employed technique is computer simulation of the integrated, dynamic system comprising the occupants, the building and its heating and ventilating system. With respect to buildings and the HVAC systems which service them, the practical objective is ensuring thermal comfort while using an optimum amount of fuel. While defining the optimum had to be left for other workers, the issue of thermal comfort is addressed here. The conventional theory of thermal comfort in conditions characteristic for dwellings and offices assumes steady-state conditions. Yet thermal conditions in buildings are seldom steady, due to the thermal interaction between building structure, climate, occupancy, and auxilliary systems. A literature review is presented regarding work on thermal comfort, specifically undertaken to examine what fluctuations in indoor climate may be acceptable. Form the results, assessment criteria are defined. Although its potentials reach beyond the area of Computer Aided Building Design, a description is given of biulding and plant energy simulation within the context of the CABD field of technology. Following an account of the present state-of-the-art, the choice for starting from an existing energy simulation environment (ESPr) is justified. The main development areas of this software platform - within the present context - are identified as: fluid flow simulation, plant simulation, and their integration with the building side of the overall problem domain. In the field of fluid flow simulation, a fluid flow network simulation module is described. The module is based on the mass balance approach, and may be operated either in stand-alone mode of from within the integrated buiding and plant energy simulation system. The program is capable of predicting pressures and mass flows in a user-defined building / plant network comprising nodes (i.e. buiding zones, plant components, etc.) and connections (i.e. air leakages, fans, pipes, ducts) when subjected to lfow control (eg thermostatic valves) and/or to transient boundary conditions (eg due to wind). The modelling and simulation techniques employed to predict the dynamic behaviour of the HVAC system, are elaborated. The simultaneous approach of the plant and its associated control is described. The present work involved extensions to the ESPr energy simulation environment with respect to robustness of the program, and with respect to additional plant simulation features, supported plant component models and control features. The coupling of fluid flow, plant side energy and mass, and buiding side energy simulation into one integrated program is described. It is this "modular-simulatneous" technique for the simulation of combined heat and fluid flow in a building/plant context, which enables an integral approach of the thermal interaction of building structure and hvac system. A multistage verification and validation methodology is described, and its applicability to the present work is demonstrated by a number of examples addressing each successive step of the methodology. A number of imaginary and real world case studies are described to demonstrate application of the present work both in a modelling orientated context and in a building engineering context.; ;

Hensen, J. Modelling coupled heat and air flow: ping-pong vs onions. in 16th AIVC Conference. 1995: AIVC.

Herrlin, M.K. and F. Allard, Solution Methods for the air balance in multizone buildings. Energy and Buildings, 1992. Vol. 18: pp 159-170.Air infiltration programs establish infiltration and ventilation rates in a building by the solution of a nonlinear system of equations. This paper discusses various modifications of the Newton-Raphson method and the special characteristics of the resulting linear system of equations. The air of the paper is selecting efficient and robust methods to solve the system of equations representing the airflow distribution in multizone buildings. Taking into account the special characteristics of the system of equations, we recommend a skyline-Cholesky's method for the linear solver. This method can be used in a general way for these problems and it appears to be very efficient in avoiding unnecessary operations on zero elements. The choice of an under-relaxation process to ensure the convergence and efficiency is not obvious. Two different methods are used to find the under-relaxation coefficients. The extrapolated method uses two steps of fixed-point iteration to calculate the starting value for the next step of the process. The optimized method uses a search routine where the direction of search is determined by Newton-Raphson and the distance of movement is determined by minimization of a related one-dimentional function. In studying the methods on the same sample of test cases, we found that they azRE very similar regarding CPU time. However, the optimized method appears to be safer and more efficient in the resolution of the nonlinear system. We, therefore, recommend using the optimized method for the nonlinear solver.

Herrlin, M.K., Air-Flow Studies in Multizone Buildings - Models and Applications, . 1993, Royal Institute of Technology.

Herrlin, M.K., Multizone Airflow and Contaminant Modelin: Performance of Two Common Ventilation Systems in Swedish Apartment Buildings. ASHRAE Transactions, 1999. Vol. 105(1).The goal of this work was to assess the performance of two common ventilation systems, an exhaust and an exhaust-supply system, in Swedish apartent building. Since correct air-exchange ain interzonal airflows are important for removing contaminants and improving indoor air quality, these airflows were analyzed by systematic computer calculations when selected input parameters were varied around their default values. The research specifically involved establishing characteristics of a prototypical building, determining appropriate boundary conditions (climate and operation), developing necessary physical/mathematical models, and establishing a protocol for carrying out the parametric studies required to assess airflow in buildings of this type.

Jones, P.J., G. Powell, and D.K. Alexander, The energy impact of ventilation on industrial buildings. 14th AIVC Conf., 1993. Vol. 1.A combined thermal and ventilation model has been used to investigate the seasonal variation of air infiltration rates and ventilation heat losses inmodern industrial buildings. The model was initially compared to measurements of ventilation rates, temperatures and heating loads in such a buildng, and was found to agree well. The model was then used to predict infiltration rates, temperatures, ventilation heat losses and space heating loads for a standard heating season for that building. The effects of variation in the building airtightness, and of the intermittent use of the loading door were also investigated. The results indicated that modern design and construction practices could significantly reduce infiltration and so reduce energy use.

Kafetzopoulos, M.G. and K.O. Suen, Coupling of thermal and airflow calculation programs offering simultaneous thermal and airflow analysis. Building Serv. Eng. Res. Technol., 1995. Vol. 16: pp 33-36.This paper assesses the feasibility of coupling a thermal simulation software (Apache) with a multi-zone airflow software (Swifib). The simultaneous multi-zone airflow and thermal analysis is particularly important in large enclosure buildings, such as atria. The study highlights the need for such analysis and shows that a new generation of combined thermal and airflow software can be produced by coupling the currently available thermal and airflow simulation software together. The combined software provides the design engineers with a fast, effective and computationally less demanding tool for analysing the performance of the built environment.

Kerestecioglu, A., et al., Modeling Heat, Moisture and Contaminant Transport in Buildings: Toward a New Generation Software. 1989.This paper describes a general purpose software, FSEC 1.1, that is capable of solving various transport equations used in building science( eg, combined heat and moisture transfer, fluid flow, contaminant dispersion).  The governing equations are solved by finite element methods. General capabiolities and an overview of the software structure are given.  Results are presented for several types of combined heat and moisture transfer simulations: 1) in buldings; 2) in the presence of natural convection; 3) in a typical wall.; ; Software developed by modifying TARP.

Klobut, K., Distribution of Contaminants in Buildings by Air Recirculation and Other Airflows. 1991, Helsinki: Helsinki University of Technology. 107.The computer program was developed for simultaneous dynamic simulation of contaminant concentrations, pressure distribution, airflows and temperatures in multizone buildings. Physical coupling existing between thermal behaviour of building structure and interzonal air movements has an impact on the distribution of contaminants in building. Consideration of this coupling in the calculation method used in the program is a considerable improvement when compared to other hitherto published programs of the same field. Network  model was used for simulation of a building. Using extracts from the program SMOV the procedure was developed for calculating the pressure distribution in the network and resulting one-way airflows. Two-way airflows through large openings were calculated according to the method used earlier in the program MULTIC. The procedure for calculating the temperatures was developed using the thermal model of a room presented earlier in literature. An estimation of the temperature gradient in the room was enabled by permitting the room air to the theoretically divided into vertically stacked zones. The program is able to handle three source-strength / contaminant-concentraiton units. Air quality is evaluated if concentraitons are calculated using pol units. The reliability of the program was tested in a number of validation cases and very good agreement was obtained between the simulation results and comparison data. An example building was used in simulations. The dynamic distributions of contaminant concentrations in the building were determined in several setups of positions of doors, with and without the return air and with different thermal loads. The simulation results emphasized the importance of simultaneous calculation of temperatures and airflows. The present version of the program works well and may readily be used for research purposes. An extensive validation by means of measurements should be performed before it could be applied for design purposes.; ;

Klobut, K., et al., Simultaneous Calculation of Airflows, Temperatures and Contaminant Concentrations in Multi-zone Buildings. 12th AIVC Conf., 1991: pp 103-122.The computer programs published so far have enabled the calculation of airflows at constant temperatures or of air temperatures at constant airflows. The first version of a new microcomputer program has now been developed in which the airflows and temperatures are calculated simulttaneously. The time-dependency of temperatures, airflows and contaminant concentrations is considered in the calculation method. The source strength of contaminants, outdoor air temperature, wind velocity and direction, convection and radiation loads can all be freely scheduled. The supply air temperature in mechanical ventilation can be selected as: (1) constant (and scheduled), (2) equal to that of the outdoor air, (3) calculated as the temperature of the mixture of outdoor air and return air. Constant temperature cases were simulated with the program and the results compared with those obtained from more sophisticated programs. Other cases, with variable temperatures, were compared with the measurements. Good agreement of the results was obtained in all cases. the paper describes the main features of the new program and gives some simulation results.

Klobut, K., Theoretical Evaluation of Impact of Return Air and Thermal Load on Air Quality in a Multizone Building. ASTM STP 1205, 1993: pp 158-172.The computer programs published so far enabled the computation of airflows assuming constant temperatures or the calculation of air temperatures assuming constant airflows. Recently, a new microcomputer program was developed in which thermal conditions were considered when predicting the spread of contaminants in buildings. The program enabled simultaneous dynamic simulations of contaminant distribution, airflows, and temperatures in a multizone building. Using the new program, the dynamic distributions of contaminant concentrations oand air quality in an example building were determined with and without the recirculation of ventilation air, with different thermal loads and with several door positions. for comparison, some simulations were repeated in isothermal conditions. The results showed that a high thermal load increased the spread of contaminant. Recirculation of the ventilatoin air had a deteriorative impact on the air quality in the simulated building. There was a clear difference in the air qualities predicted by the respective simulations carried out with and without thermal analysis. It is believed that the inclusion of thermal analysis considereably improved the calculation method for the evaluation of contaminant distribution in a building.

Klote, J.H. and J.A. Milke, Design of Smoke Management Systems. 1992: ASHRAE.ASHRAE Special Publication that presents an excelent overview of "state-of-the-art" in design of smoke management systems. John Klote is the author of ASCOS which is a multizone modeling tool created for analyzing smoke management systems.

Kronvall, J. and A. Blomsterberg. Performance of passive stack ventilation in a single-family house: a computational simulation study. in 16th AIVC Conference. 1995: AIVC.

Lansari, A., et al., Dispersion of automotive alternative fuel vapors within a residence and its attached garage. Indoor Air, 1996. Vol. 6: pp 118-126.

Li, Y., Predictions of IAQ in multi-room buildings. Indoor Air 93, 1993. Vol. 5: pp 557-562.3 indoor air problems in multiroom buildings are simulated by a multizone air flow model and an air quality model. They are: odor complaints by the occupants in a Swedish single family house; moisture content vs time relationships for kitchen air; and radon concentrations in a residence with an oil-burning heating system. Suggestions have been made to improve IAQ in these buildings. Both the air change rates and air flow direction have considerable influence on the concentratin of pollutants produced in buildings and could be used effectively to control the accumulation of such pollutants. The level of air in the distribution of leakage or an opening can result in a different air flow rate and direction; and thus a different level of iaq.

Li, Y. and S. Holmberg, General flow- and thermal-boundary conditions in indoor air flow simulation. Indoor Air 93, 1993. Vol. 5: pp 551-556.The concepts of general flow and thermal boundary conditions are introduced to treat interaction between indoor and outdoor thermal environments in CFD simulations. The results from a multizone model are used to supply the general flow boundary conditions. The energy balance equation at wall-air interface is used to supply the general thermal boundary conditions. An example calculation in a 13 room building shows that infiltration influences indoor air flow patterns considerably. The air flow in a room with 2 surface coatings ventilated by displacement is measured and simulated. Implementation of these 2 boundary conditions is essential in predicting air flow pattern, air quality, and thermal comfort in a real building.

Liddament, M., Annex 23 Multizone Air Flow Modelling - A New IEA Annex. Air Inf. Rev., 1990. Vol. 12: pp 6-7.

Mansson, L.-G., Evaluation and demonstration of domestic ventilation systems - State of the Art, . 1995, Swedish Council for Building Research.

Milke, J.A., Using Models to Support Smoke Management System Design. Fire Protection Engineering, 2000(Summer 2000 Number 7): pp 17-22.A review of the types of modeling/simulation tools available to the designers of smoke management systems. Includes the use of small scale models, computer-based zone models, CFD models and network airflow models (e.g. CONTAM).

Modera, M.P. and R. Jansky, Residential Air-Distribution Systems: Interactions with the Building Envelope. TPoEEB, 1992. Vol. V: pp 623-631.Residential ADS, used both for heating and cooling and less commonly for ventilation, have important interactions with the building envelope. These systems can either be enclosed withing the envelope or pass outside the envelope (in which case they represent an extension of the envelope). This paper addresses the three major types of interaction between ADS that pass outside the envelope and sigle-family buildings: 1) duct leakage and duct conduction when the distribution fan is off, which act like a thermal bridge in the envelope; 2) duct leakage during system operation, which creates large changes in the quantity and location of air infiltration and exfiltration through the envelope; and 3) supply/return flow imbalances within individual zones during fan operation, which create elevated envelope pressure differentials, infiltration rates, and exfiltration rates. A simulation tool that was developed to take into account all of these interactions is presented and applied. The simulation tool - which is based upon the DOE-2 thermal simulation model, a multizone airflow network model (COMIS), and an equipment model for the ducts - is used to examine the magnitude of all 3 interactions. The interaction issues examined include air infiltration/exfiltration magnitude and location, overall thermal exchange when the system is off, and air exchange when the system is operating, with and without internal doors closed. The most surprising result of the analyses presented was that the thermal siphon effect for perfectly sealed ducts was shown to have an impact on heat exchange between the house and unconditioned spaces that can be more thatn 4x larger than that due to typical duct leakage when the fan is not in operation. This result suggests that this issue merits more careful examination than it has received in the past.

Molhave, L., et al., The Danish twin apartment study - part II: Mathematical modeling of the relative strength of sources of indoor air pollution. Indoor Air, 1996. Vol. 6: pp 18-30.

Moser, A., The Message of Annex 20: Air Flow Patterns Within Buildings. 12th AIVC Conf., 1991. Vol. 1: pp 1-26.The IEA task-sharing project "Air flow within buildings: was initiated in May 1988 for a duration of 3 1/2 years. 12 nations contribute work and expertise and "share the task" specified in the project's objectives. This project and the AIVC belong to the same Implementing Agreement. As "Attachments to the Implementing Agreement, they are called Annexes. The general objective of the Annex is to evaluate the performance of single- and multi-zone air and contaminant flow simulation techniques and to establish their viability as design tools. To reach this goal, the work was divided into two parallel subtasks: one on single-room air and contaminant flow and the other on multi-zone air and contaminant flow and measurement techniques. This survey paper reviews project objectives and approach, both technically and from the point of view of project management. It offers an overview of the work performed and solutions contributed by the participating countries, it discusses problems encountered during the project and how these were solved, and summarizes final results. It shows how the various technical Annex 20 contributions to this conference are related to the overall Annex effort. General conclusions are drawn, consequences for future international projects are examined, and the main message of the multi-national program is formulated.

Musser, A. and G. Yuill, Comparison of Residential Air Infiltration Rates Predicted by Single-Zone and Multizone Models. ASHRAE Transactions, 1999. Vol. 105(Part 1).Compares use of multizone model (CONTAM) and single-zone model (LBL model) in predicting infiltration rates of a single-family residential building. Fan pressurization measurements were made. Multizone model of the house consisted of over 2,000 zones and 7,000 leakage paths. Four different ventilation configurations were simulated including no mechanical ventilation or exhaust, supply fan only, exhaust fan only, and balanced supply and exhaust fans. Observations were made with respect to wind-related input parameters, envelope leakage distribution and utilizing both single-zone and multizone models to achieve simulation results faster than using only the multizone model.

Musser, A. Multizone Modeling as an Indoor Air Quality Design Tool. in Proceedings of Healty Buildings 2000. 2000. Espoo, Finland.Increased public awareness and changing industry standards have highlighted the importance of indoor air quality in the building design process.  At the same time, many owners would like to construct buildings that conserve energy and minimize environmental impact.  To accomplish both of these goals, the designer must be able to understand airflow rates, pressure relationships, and contaminant transport in buildings.  This paper describes the use of a multizone model to perform design calculations for a new building on a college campus in the United States.  The building incorporates a number of environmentally "progressive" features, such as natural ventilation, energy recovery, a biological wastewater treatment process, and CO2 demand controlled ventilation.  The multizone modeling tool CONTAM is used to size an exhaust fan for source isolation, select minimum ventilation quantities to control building related contaminants, and specify procedures for flushing out contaminants prior to occupancy.  The multizone model is also used to predict transient contaminant levels, taking into account weather and associated infiltration.  The generalization of these design and analysis techniques to a wider range of indoor air quality design applications is also discussed.

Nantka, M.B., New concepts aimed to improve the multizone model for predicting the air flows in the buildings. Indoor Air 93, 1993: pp 563-568.Computer simulation is one of the basic means to obtain complex information concerning the air flows in a multizone building structure.  Presented briefly in this paper are the fundamentals of the newly developed simulation method.  The major departures are addressed which distinguish this new method from the other multizone models.  These include the principles of dividing a building into zones and the accomplishment of the simulation of the system.  Attention is paid to the universality of the new method, the flexibility in regard to modifications and the usefulness in mathematical verification of other simulation results.

Nantka, M.B. Evaluation of wind pressure effects on ventilation rates in multizone dwelling houses. in Roomvent 94. 1994.

Okuyama, H. New Progress on the Multi-chamber Airflow Measurement  System. in International Symposium on Room Air Convection and Ventilation Effectiveness. 1992. Tokyo, Japan: Society of Heating, Air Conditioning and Sanitary  Engineers of Japan.The measurement method for multi-chamber airflow is an  important research theme because of the limitations and errors  inherent in conventional single chamber method. The fundamental  theory for this measurement and several application examples by the  have been published. The theory is based on the tracer gas  dispersion general model in multi-chamber system called Thermal  Network state equation which is also applicable to heat transfer  system. To estimate the airflows in multi-chamber system is  considered as a type of system identification of the state equation  model and two calculation procedures have been deduced from the least  squares method. Several field measurements and verificational test  have shown the practicality, accuracy and also defects of the  measurement system. In the present paper some improvements on these  defects and the verification in the field measurement are described.

Orme, M., A Comparison of Multi-zone Air Flow Models - Annex 23 Report. 1994.The purpose of this section is to report on a comparison of the results of several multizone air flow models which have been configured using the same sets of input data. The results are presented below in Section V, in the form of mass flow rates through every leakage path, for each of the models. It was not intended to test the full capabilities of each model, and therefore only a straightforward configuration was devised for the test. It was found that when identical data are applied to each model, the variations between the total outgoing air flow rates predicted by the models were low, shoen in Table 2, as were the variatins for the individual zones. In absolute terms, the standard deviation of the results for each opening was low in magnitude and reasonably constant. On the other hand, the relative spread of the values around the mean value was significantly higher for some openings, in particular for path 9.; ;

Owen, M.K., et al., Predicting indoor air quality with IAQPC. Proceedings of the Jacques Cartier Conference, 1992: pp 101-108.The ability to predict the level of air contamination for any building for known sources and air cleaners has long been desired.  IAQ consultants, building occupants, and especially, building designers and builders must be able to predict what type of indoor environment will result from their decisions.  This paper presents the results of a model study using the IAQPC.  The building modeled is a test house characterized in several studies.  Experimental values for air cleaners efficiencies, source strengths, and ventilation rates have been combined to predict the contamination level in the house.  In particular this paper addresses the effect of vacuum cleaning and cigarette smoking on a home's air supply and investigates the results of employing furnace filters relative to an ASHRAE rated filter and an electronic air cleaner.

Passard, J., Analysis of air circulation through a building. Bldg Res & Pract, 1990.This paper provides a detailed acount of the development of a numerical model for estimating the airflow rates through openings and cracks in the building envelope.

Pelletret, R.Y., Internal Heat Transfers and Heating Needs of Buildings. ICBEM'87, 1987. Vol. 2: pp 121-128.

Pelletret, R. and H. Khodr, Development and Validation of New Aeraulic Model Designed for Thermal Computation with Particular Attention to the Problems of Air Quality. Bldg Res & Pract, 1990.The air flows in large openings, due to the buoyancy effect, can reach high values in comparison iwth the values of the air flows due to air leakage and ventilation. For example, through a standard opening, a difference of temperature 0.1 creates a circulation of air of about 120 m3/h. A difference of 1 in temperature creates an air circulation of about 390 m3/h. The buoyancy effect plays a major role in the diffusion of pollutants. To model the influence of the buoyancy effect, simplified models can sometimes be used. Such a model has been designed and partially validated. Its application field for the computation of air flows is limited to the case when the temperature profiles in the rooms are almost linear, and there is no multiple neutral plane. If there is a multiple neutral plane, the air flow rates can be very important although the average temperature of the rooms are equal. If a C2 class model is inapplicable, a C3 model must be used. But, to be very accurate, the c3 model has to take into account the vertical temperature gradients in the rooms. This kind of computation is not very complicated if the temperatuire profiles are known but it becomes complicated if temperature profiles are variables. In addition, the on-going experimental study would provide some data to velidate a model to compute the discharge coefficient of the large openings. Some elements of reflection could be provided about the physical mean of the discharge coefficient and its relevant use.

Pelletret, R., et al., The concept of Intelligent Simulation Environment. 1992.The demand for powerful and easy-to-use simulation tools is growing both in the research community and also among the professionals.  Some powerful simulation codes already exist or are under development but their use is restricted to inititated researchers circles.  Today, concepts an dtools have been developed in order to facilitate the use of these simulation codes; one of the goals of Annex 23 is to apply these new concepts ot a Multizone Air Flow an dPollutant Transport simulation code: COMIS.  The goal is to develop a socalled Intelligent Simulation Environment (ISE).  After a brief description of the existing COMIS model, the papaer focuses on the concept of ISE developed by CSTB.  The three main ideas on which this concept is built are: the sharing of data through an Integrated Data Model, the coupling of various simulation tolls via the ISE, the automatization of modelling and simulating tasks with the use of expert sytems. Briefly discusses coupling COMIS with TRNSYS.

Perera, M.D.A.E.S. and P.R. Warren, Influence of Open Windows on the Interzone Air Movement within a Semi-detached Dwelling. 6th AIC Conf., 1985: pp 9-28.In this paper, a multicell airflow computer program called BREEZE is used to determine the influence of open windows on the ventilation rates of a semidetached house for a variety of weather conditions. For a limited number of cases, the predicted values are compared with field measurements to indicate the degree of confidence which can be placed in the computer simulation. The effect of closing internal doors on ventilation rates and interzonal airflows is also considered.

Persily, A.K. and R.A. Grot, The Airtightness of Office-building Envelopes. TPoEEB, 1985. Vol. III: pp 125-143.Although airtightness, infiltration, and ventilation are important considerations in large office buildings, these issues have been studied less in office buildings than in residential buildings. Several features of office buildings make their air exchange characteristics different from homes. These features include curtain wall de4sign and construction, mechanical ventilation systems, specific occupancy patterns, large volumes and building heights, and low surface to volume ratios. The recent development of measuring procedures and computer simulation programs for large buildings has enabled the study of air leakage in large buildings and the effects of air exchange on energy use and IAQ. This paper discusses the airtightness of building envelopes in  modern office buildings and the relationship between envelope airtightness and air exchange rates. Results of whole building pressurization measurements and tracer gas measurements of air exchange rates in several office buildings are discussed, along with the relationship between these measurement results. A multizone computer simulation program developed at the NBS is applied to two office buildings to examine this relationship further. The results of the simulations reveal the importance of envelope airtightness, floor-to-floor coupling, and mechanical ventilation to the air change rates in these two buildings.

Persily, A.K., Modeling Radon Transport in Multistory Residential Buildings. ASTM STP 1205, 1993: pp 226-242.Radon concentrations have been studied extensively in single-family resdiential buildings, but relatively little work has been done in large buildings, including multistory residential buildings.  The phenomena of radon transport in multistory residential buildings is made more complicated by the multizone nature of the airflow system and the numerous interzone airflow paths that must be characterized in such a system.  This paper presents the results of a computer simulation of airflow and radon transtport in a 12 story residential building.  Interzone airflow rates and radon concentrations were predicted using the multizone airflow and contaminant dispersal program CONTAM88.  Limited simulations were conducted to study the influence of two different radon source terms, indoor-outdoor temperature difference and exterior wall leakage values on radon transport and radon concentration distributions.

Persily, A.K., A Modeling Study of Ventilation, IAQ and Energy Impacts of Residential Mechanical Ventilation, . 1998, National Institute of Standards and Technology.Based on concerns about indoor air quality and trends towards tighter envelope construction, there has been increasing interest in mechanical ventilation in residential buildings. A variety of ventilation approaches have been examined through both field measurements and computer simulation studies. This paper reports on a simulation study of indoor air quality, ventilation and energy impacts of several mechanical ventilation approaches in a single-family residential building. The study focused on a fictitious two-story house in Spokane, Washington and employed the multizone airflow and contaminant dispersal model CONTAM. The model of the house included a number of factors related to airflow including exhaust fan and forced-air system operation, duct leakage and weather effects, as well as factors related to contaminant dispersal including adsorption/desorption of water vapor and volatile organic compounds, surface losses of particles and nitrogen dioxide, outdoor contaminant concentrations, and occupant activities. The contaminants studied include carbon monoxide, carbon dioxide, nitrogen dioxide, water vapor, fine and coarse particles, and volatile organic compounds. One-year simulations were performed for four different ventilation approaches: a base case of envelope infiltration only, passive inlet vents in combination with exhaust fan operation, an outdoor intake duct connected to the forced-air system return balanced by exhaust fan operation, and a continuously-operated exhaust fan. Results discussed include whole building air change rates, air distribution within the house, heating and cooling loads, contaminants concentrations, and occupant exposure to contaminants.

Persily, A.K. and S.R. Martin, A Modeling Study of Ventilation in Manufactured Houses, . 2000, National Institute of Standards and Technology: Gaithersburg.The HUD Manufactured Home Construction and Safety Standards (Part 3280, 1994) contain requirements intended to provide adequate levels of outdoor air ventilation in manufactured homes. In the implementation of these standards, questions have arisen regarding the impact and significance of some of these requirements. Some of these questions relate to the actual ventilation rates in homes built to the standards and the means of providing supplemental mechanical ventilation to meet the requirements of the standards. Other questions have arisen as to how specific ventilation system components such as duct leakage, local exhaust fans and ventilation inlets affect ventilation rates, air movement patterns, and building pressures. In order to obtain some insight into these issues, the multizone airflow and indoor air quality program CONTAM was used to simulate a double-wide unit under several different ventilation scenarios. These scenarios include envelope infiltration only, infiltration plus the effects of local exhaust and forced-fan operation, an outdoor air intake duct installed on the forced-air return, and whole house exhaust with and without passive inlet vents. Simulations were performed to predict outdoor air ventilation rates into the house due to infiltration and mechanical ventilation, interzone airflow rates between the rooms, building air pressures, and ventilation air distribution. Annual simulations were performed in three cities to assess ventilation rates and energy consumption associated with these scenarios. The results show that despite the assumption in the HUD standards that infiltration contributes 0.25 h-1, the predicted infiltration rates are lower than this value for many hours of the year. The supplemental ventilation systems investigated in this study provide ventilation rates that meet or exceed the total ventilation requirement of 0.35 h-1, but the impacts of such systems are dependent on their operating schedules. In addition, in these simulations, the impacts of a whole house exhaust fan are independent of whether this fan is located in the main living area or in a bathroom off the main living area. Also, for the case of ventilation with a whole house exhaust fan, the inclusion of passive inlet vents is not critical given the level of envelope airtightness used in these simulations. The results of these simulations are presented and discussed, and recommendations are made for changes to the HUD standards and for future research.

Phaff, J.C. and W.F. de Gids, Airflow Driven Contaminants. Transport through Buildings. ANNEX 20 Subtask 2.5. 12th AIVC Conf., 1991: pp 123-140.Air is the main transport for contaminants in buildings. Minimizing source strengths has first priority, second is to control air flow rates, supply and exhaust, and directions between zones in buildings.    Computer simulation models for ventilation and pollutant spread in buildings have been proven to give useful predictions. Large measurement campaigns for optimizing ventilaiton and pollutant problems are complex and expensive. They are often jammed by too many vague parameters influencing the result. The computer models are an alternative and form a supplement to measurements. New ventilation systems or control strategies can be tested to some extent with the models. Measurements for checks and determination of source and sink coefficients for different materials are needed to tune the simulation models.

Rao, J. and F. Haghighat, A procedure for sensitivity analysis of airflow in multi-zone buildings. Building and Environment, 1993. Vol. 28(1): pp 53-62.

Reusing, G.L. and G.M. Bragg, A Multi-Chamber Ventilation Model with Random Parameters. Bldg. & Env., 1990. Vol. 25: pp 339-347.A generalized multi-chamber model is developed for air contaminant prediciton problems where the parameters of the system, such as airflow rates, are described by Gaussian probability distributions. A numerical solution, utilizing stochastic differential equations, is provided to facilitate its application. The model is used to calculate contaminant concentration histories described by means and standard deviations. It is also used to show the sensitivity of concentrations to the variation of such parameters as infiltration flows and contaminant source rates. Sample applications of the model are provided.

Rodriguez, E.A. and F. Allard, Coupling COMIS airflow model with other transfer phenomena. Energy and Buildings, 1992. Vol. 18: pp 147-157.One of the main characteristics of thermal and fluid mechanical behaviour of buildings is that it is dominated by coupled heat and mass transfer phenomena. In this paper we describe the main phenomena influencing the behaviour of buildings and propose a general formulation of these coupled phenomena. We then apply this formalism to two important problems. The first one deals with the coupling between a multizone thermal model and a multizone airflow model. The second one presents the coupling between the transport fo pollutants and airflow calculation in a multizone building. In order to illustrate our proposition we give various kinds of examples of coupled configuration.

Said, M.N.A. and R.A. MacDonald, An evaluation of a network smoke control model. ASHRAE Transactions, 1991. Vol. 97: pp 275-282.This paper describes the evaluation of the air and smoke movement model developed at a Canadian research institute. To verify the model, predicted data are compared with data from full-scale fire tests involving a pressurized stair shaft smoke control system. The tests were conducted in the 10-story experimental fire tower at the National Fire Laboratory of the National Research Council of Canada. Predicted data exhibit good agreement with measured data. The paper also discusses the effects of large exterior and interior openings and the pressure due to the fire on the building's pressures and on smoke migration.

Said, M.N.A., et al., Computer simulation of ventilation strategies for maintaining an acceptable indoor air quality in office buildings. ASHRAE Transactions, 1995: pp 1118-1125.

Sandberg, M., The Multi-chamber Theory Reconsidered from the Viewpoint of Air Quality Studies. Bldg. & Env., 1984. Vol. 19: pp 221-233.A general multi-chamber model is presented and explored form the viewpoint of air quality studies. The model involves the following key concepts: purging flow rate and age distribution of both air and contaminants. From the physical and mathematical properties of the model, are deduced estimates of the magnitude of, and the relations between, the key concepts. The practical use of the model is illustrated.

Sauer, H.J. and R.H. Howell, Estimating the indoor air quality and energy performance of VAV systems. ASHRAE Journal, 1992. Vol. 34:7: pp 43-50.VAV system simulation program based on AIRNET,

Schaelin, A., et al. A new method for linking results of detailed air flow pattern calculation with multizone models. in 13th AIVC Conference. 1992. Nice, France: AIVC.Multi-zone models are a common tool for calculating air and contaminant exchange within rooms of a building and between building and outdoors. Usually a whole room is then modelled by one calculation node with the assumption of homogeneously mixed conditions within this room whereas in real cases temperature and contaminant concentrations vary in space. The exchange to the neighbouring nodes via the flow paths is then a function of the local values of these variables.  Detailed knowledge can be obtained from the solution of the transport equations for the airflow pattern within the room at the expense of far higher computation cost.  This work shows a new approach called "method of detailed node values" to include results from detailed calculations in multi-zone models to give a better description of the real cases.  Parameter transfer between a multi-zone program and a detailed air flow simulation program is discussed for different flow paths of practical importance. The method is demonstrated in an example case with air in/exfiltration, ventilation and contaminant propagation, and discussed in a second example with large openings.  This new method promises to improve the multizone model predictions with few additional CFD computations.

Schaelin, A., et al., Application of a new method for improved multizone model predictions. 14th AIVC Conf., 1993. Vol. x: pp x.This work shows the application to several examples of a new method which includes results from detailed calculations for oe room of importance in a multizone model of a whole building. The examples with air in/exfiltration, ventilation and contaminant propagation show the effects on the results of the predictions of the air flow and the contaminant spread by relaxing the homogeneity assumptions. The proposed name of the method is 'detailed flow path value method' (DFPV) as separate local variable values are considered for each flow path from the room of importance to the neighbouring rooms instead of one average value. It is discussed in which situations the DFPV method can be expected to improve the multizone model predictions.

Schaelin, A., et al., Improvement of multizone model predictions by detailed flow path values from CFD calculations. ASHRAE Transactions, 1993. Vol. 99-2.Multizone models are a common tool for calculating air and contaminant exchange within the rooms of a building and between a building and the outdoors.  Usually a whole room is modeled by one calculation node with the assumption of homogeneously mixed conditions within this room, but in real cases, temperature and contaminant concentrations vary in space.  The exchange to neighboring nodes via flow paths is a function of the local values of these variables.  Detailed knowledge can be obtained from the solution of the transport equations for the airflow pattern (computational fluid dynamics, CFD) within the room at the expense of far higher computation costs. This work shows how results from CFD calculations can enhance the accuracy of multizone model prediction to give a better description of real cases.  Para eter transfer between a multizone program and a detailed airflow simulation program is discussed.  The method is then aplied to example cases with air in/exfiltration, ventilation, and contaminant propagation and flow through large openings and shows its ability for a more accurate prediction of the contaminant spread. In the cases shown, concentration values differ by up to a factor of 2.5 from the purely multizonal prediction is 0.12 ppm for the concentrations in a neighboring room, whereas the corresponding values of the new method vary between 0.05 and 0.23 ppm for different source positions.

Schaelin, A., et al., Improvement of Multizone Model Predictions by  Detailed Flow Path Values from CFD Calculations. ASHRAE Transactions, 1994. Vol. 100(2): pp 709-720.Multizone models are a common tool for calculating air and contaminant exchange within the rooms of a building and  between a building and the outdoors. Usually a whole room is modeled by one calculation node with the assumption of  homogeneously mixed conditions within this room, but in real  cases, temperature and contaminant concentrations vary in  space. The exchange to neighboring nodes via flow paths is a  function of the local values of these variables. Detailed knowledge can be obtained from the solution of the transport  equations for the airflow pattern (computational fluid  dynamics, CFD) within the room at the expense of far higher  computation cost. This work shows how results from CFD  calculations can enhance the accuracy of multizone model  predictions to give a better description of real cases.  Parameter transfer between a multizone program and a  detailed airflow simulation program is discussed. The method is then applied to example cases with air  in/exfiltration, ventilation, and contaminant propagation  and flow through large openings and shows its ability for a more accurate prediction of the contaminant spread.   In the cases shown, concentration values differ  by up to a factor of 2.5 from the purely multizonal  approach. In the case with open windows, the multizonal prediction is 0.12 ppm for the concentrations in a  neighboring room, whereas the corresponding values of the new method vary between 0.05 and 0.23 ppm for different  source positions.

Schalin, A., et al., A New Method for Linking Results of Detailed Air Flow Pattern Calculation with Multizone Models. 13th AIVC Conf., 1992: pp 63-76.Multizone models are a common tool for calculating air and contaminant exchange within rooms of a building and between bulding and outdoors. Usually a whole room is then modelled by one calculation node with the assumption of homogeneously mixed conditions within this room whereas in real cases temperature and contaminant concentrations vary in space. The exchange to the neighbouring nodes via the flow paths is then a function of the local values of these variables. Detailed knowledge can be obtained from the solution of the transport equations for the air flow pattern within the room at the expense of far higher computation cost. This work shows a new approach called "method of detailed node values" to include results from detailed calculations in multizone models to give a better description of the real cases. Parameter transfer between a multizone program and a detailed air flow simulation program is discussed for different flow paths of practical importance. The method is demonstrated in an example case with air in/exfiltration, ventilation and contaminant propagation, and discussed in a second example with large openings. This new method promises to improve the multizone model predicitons with few additional CFD computations.

Schneider, P.S., J.-J. Roux, and J. Brau, Strategies for Solving the Air Flow-Thermal Problem in Multiroom Buildings. Bldg. & Env., 1995. Vol. 30: pp 277-286.Iterative and direct methods for solving the coupled problem of heat and mass transfers in buildings are presented and compared. Numerical problems often trouble the resolution of this problem and a choice between different strategies can be a way to overcome instabilities of calculus and running-time difficulties. The state of the zones of air is represented as a function of temperature and pressure. The iterative method consists of separating the problem into two subsets, the first being a function of temperature and the other a function of pressure. The direct method simultaneously carries out the resolution of the original set. Two simulation codes were developed based on the 'coupling method', which is a method of solving the thermal problem by splitting it into levels of coupleing. The direct option needs more computational effort, but is easier to run by non-experts. In contrast, the iterative method is better adopted to the connection of different programs. Simulation results are presented, and the performances of the two strategies are compared and discussed.

Sibbitt, B.E. and T.L. Hamlin, Meeting Canadian Residential Ventilation Standard Requirements with Low-cost Systems. ASHRAE Transactions, 1991. Vol. 97, Pt 2.Several low-cost ventilation systems, intended to meet the continuous-ventilation requirements specified in the Canadian residential ventilation standard, CSA F326, were investigated. 8 ventilation system configurations were installed, commissioned, and tested in the field to obtain operating experience withthe syustems and to establish confidence in the simulation software. CO2 and HCHO levels were simulated inhouses with several different ventilation system configurations. The cases modeled included houses with and without forced-air recirculation systems, average and tight building envelopes, and average and heavy occupancies. It was determined that several low-cost techniques, including fan-driven limited-distribution systems combined with one or more exhaust fans, canbe effective in providing good indoor air quality control, while some other techniques should not be relied on. Examination of continuous CO2 measurements in 2 mechanically ventilated houses suggested that the fresh air supply rates specified by CSA F326 provide good control of this contaminant.

Sparks, L.E., M.D. Jackson, and B.A. Tichenor, Comparison of EPA Test House Data with Predictions of an Indoor Air Quality Model. IAQ 88, 1988: pp 251-264.An easy-to-use iaq model is described. It is a multi-component model based on a well-mixed mixing model. Sources and sinks are allowed in each compartment. A menu-driven fill-in-the form user interface is used to control program flow and obtain data from the user. On-screen graphical output is provided. The model estimates the effects of HVAC, air cleaning, room-to-room air movement, and natural ventilation on pollutant concentrations. Experiments conductd in the EPA test house using moth crystal cakes for model verification are described. The agreement between small chamber emission factors, model predictions, and test house data is very good. Predicted weight loss of the moth crystal cakes was within 5 % of the measured weight loss. Predicted room concentrations of p-dichlorobenzene are within 20 % of the measured values. Future directions for model development and experimental studies are discussed.

Sparks, L.E., et al., Verification and uses of the environmental protection agency (EPA) IAQ model. IAQ 89, 1989: pp 146-150.This paper describes a set of experiments used to verify an IAQ model for estimating the impact of various sources on IAQ in a multi-room building.  The model treats each room as a well mixed chamber that contains pollutant sources and sinks.  The model allows analysis of the impact of room-to-room airflows, HVAC systems, and aircleaners on IAQ.  The model is written for personal computers. The experiments were conducted in a test house.  3 different pollution sources were used in the experiments - moth crystals, kerosene heaters, and drycleaned cloths.  The model predictions were in good agreement with the experimental data, especially when a sink term was included in the model. The paper presents a brief discussion of the theory on which the model is based.  Preliminary data and theory of sources and sinks are also discussed.  Examples demonstrating the use of the model to analyze IAQ control options and to estimate exposure from a pollutant are included.

Sparks, L.E., et al., An Integrated Approach to Research on the Impact of Sources on Indoor Air Quality. Indoor Air 90, 1990.An approach for analyzing the impact of sources on IAQ based on chamber studies, modeling, and test house studies is described. Source emission factors are developed in chamber studies. The emission factors are used in an IAQ model that incorporates room-to-room air movement, sinks, and air exchange with the outdoors to predict indoor air pollution concentrations from the source. Test house experiments are used to verify the model and identify unmodeled factors. The agreement between model predictions based on chamber emission factors and test house data is excellent.

Tichenor, B. and L. Sparks, Managing exposure to indoor air pollutants in residential and office environments. Indoor Air, 1996. Vol. 6: pp 259-270.

van der Maas, J. and C.-A. Roulet, Multizone cooling model for calculating the potential of night time ventilation. 14th AIVC Conf., 1993. Vol. 1.One of the options to increase the energy efficiency of buildings in the cooling season, is to extract heat from the building envelope during the night by natural or forced ventilation. The exploitation of this technique by architects and designers requires the development of guide lines and a predesign tool showing how the potential cooling power depends on the influence of opening sizes and positions and on the interaction with the thermal mass. While a single zone model is sufficient to estimate roughly the heat extracted form the building, a multizone extension allows one to predict the distribution of air and wall temperatures and therefore the distribution of cooling power over the air flow path (when the zones are ventilated in series. A zonal cooling model based on the principles of mass and energy conservation and coupling ventilation with both heat transfer and a thermal model for the walls. The parameters of the ventilation model are the size and position of the openings, the stack height, and climatic parameters like temperature swing and wind characteristics. The heat transfer is parametrized by the exposed surface area of thermal mass, while the heat storage for heavy weight constructions is only characterized by both that surface area and the thermal effusivity of the exposed wall material. The predictions are compared with measurements for a simple flow path configuration.

Walker, L.S., Distribution System Leakage Impacts on Apartment Building Ventilation Rates. ASHRAE Transactions, 1999. Vol. 105(1).Forced air distribution systems in residential buildings are often located outside the conditioned space, for example, in attics, crawl spaces, garages, and basemets. Leaks from the ducts to these unconditioned spaces or outside can change flows through the registers and change the ventilation rates of the conditioned spaces. In this study, duct leakage flows were measured in several low-rise apartment buildings. The leakage flow measurements and other data about the apartments were used to develop a prototype apartment building. The multizone arflow model COMIS was then used on this prototype building to determine internal flows within the building, airlflows through the building envelope, and the impacts of the duct leakage on the ventilation rates. The effects of sealing the duct leaks were also examined in order to determine changes in infiltration rates resulting from duct retrofits. The simulation results showed that for the prototype tested here, the excess return leakage tended to decrease envelope infiltration flows by about 20%, but the total infiltration load, including return duct leaks, more than doubled during system operation.

Walton, G.N., AIRNET - A Computer Program for Building Airflow Network Modeling, . 1989, National Institute of Standards and Technology: Gaithersburg.

Walton, G.N. CONTAM94: A Multizone Airflow and Contaminant Dispersal Model with a Graphic User Interface. in Building Simulation '95 - Proceedings of 4th Conference of International Building and Performance Simulation Association. 1995. Madison, WI: IBPSA.CONTAM94 is an easily used, public domain airflow and contaminant migration analysis proram combining algorithms for modeling airflow and contaminant dispersal in multizone buildings. It employs a simplified graphic description of the building for both data entry and the presentation of simulation results. It runs on commonly available 486DX calss PC compatible computers with VGA graphics and MS-DOS. It can handle buildings containing a large number of zones.

Walton, G.N., CONTAM96 User Manual, . 1997, National Institute of Standards and Technology: Gaithersburg.This manual describes the use of a computer program, CONTAM96, for analyzing the air movement and indoor air quality in multizone buildings.  The program is used to create and edit the building description including data for all features relating to airflow or to the generation and removal of contaminants.  It uses a graphic interface to establish the spatial relationship of these features.  These data along with weather data are used to calculate the airflows and dynamic levels of indoor contaminants.  The results of the calculation may be reviewed graphically and printable files may be generated.  This program is an extension of the earlier CONTAM93 program.

Weir, B.R., et al., Specification of indoor air model characteristics. Indoor Air 90, 1990.Indoor air models are reviewed for applicability to general and specific problems of human exposure and risk.  Each model is evaluated for its suitability for driving exposure and risk analyses and for its ability to address scientific and policy issues.  The models' input data requirements are reviewed.  Factors limiting the range of applicability are identified and characterized.  Sensitivity of each of the models to input parameters is discussed.

Yoshino, H., et al., Analysis on Improvement of Residential Building Performance by Multizone Thermal and Airflow Model. ASHRAE Transactions, 1993. Vol. 99.Many factors affect the indoor environment of residential buildings. Among those factors are thermal insulation, airtightness, and the space-heating patterns. The influence of these factors on indoor thermal environment and space-heating load is investigated by a multizone thermal and airflow simulation including mutual radiation. The computer simulation was done on a model  of a detached house with 10 rooms. The results obtained from This study show the degree of the effect of these factors on thermal environment and heating load.

Yoshino, H., et al., Numerical Analysis of Ventilation System Performance by COMIS Model. ASHRAE Transactions, 1999. Vol. 105(1).This research evaluated the performance of four kinds of ventilation systems for dwellings under various conditions by means of numerical simulation. the total number of combinations of various parameters for the caculations was 174. 
Calculations were performed hourly for indoor pollutant concentration, humidity and condensation, indoor-outdoor pressure difference, airlflow rate, and heat energy by ventilation, etc., through the heating season.
A multizone infiltration and pollutant trasport model (COMIS) was used to perform the simulation. A new term, "acceptable ratio," is introduced in this study to evaluat the performance of ventilation systems from the point of view of CO2 level and energy consumption. In addition, by means of statistical methods, the effect of various factors on ventilation system performance is discussed. a set of predictive equations for ventilation systems are derived in this paper to try to evaluate ventilation system performance in an easy way under any conditions.

Yuill, G.K. and M.R. Jeanson, An analysis of several ventilation strategies for four ventilation systems. Indoor Air 90, 1990. Vol. 4.The relative performance of 2 ventilation systems in terms of energy consumption and controlling occupant exposure to indoor air pollutants was determined using computer simulations. The 2 ventilation systems modelled were; a heat recovery ventilator with a conventional forced air furnace and a continuous exhaust ventilator window system with electric baseboard heating. Each of the ventilation systems was simulated according to 2 different control strategies. One control strategy used constant exhaust fan flow rates. The other strategy operated by modulating the exhaust fan flow rates to keep the CO2 concentration in the exhaust stream constant (demand controlled exhaust). It was found in general that the continuous exhaust systems performed as well as or better than the demand controlled exhaust systems at controlling occupant exposure to the pollutants modelled.

Yuill, G.K., M.R. Jeanson, and C.P. Wray, Simulated Performance of Demand Controlled Ventilation Systems Using Carbon Dioxide as an Occupancy Indicator. ASHRAE Transactions, 1991. Vol. 97 Pt 2.A central supply ventilation system and a distributed supply ventilation system were simulated to determine their relative performance in controlling occupant exposure to indoor air pollutants. 2 different control strategies were used: (1) constant exhaust flow rates (continuous ventilation) and (2) modulation of the exhaust flow rates to keep the CO2 concentration in the exhaust airstream constant (DCV). The DCV systems showed no clear advantage over the continuous ventilation systems. They reduced the exposures to some pollutants and increased the exposures to others. In some cases, the relative performance of the DCV systems depended strongly on whether central supply or distributed supply ventilation was used.