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Bibliography A-I

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.

Arvelo, Juan, Ph.D.; Alan Brandt, Ph.D.; Robert P. Roger, Ph.D.; Anshu Saksena, An Enhanced Multizone Model and Its Application to Optimum Placement of CBW Sensors 2002, ASHRAE Annual Meeting

Enhancements have been made to the multizone flow model CONTAM to incorporate estimates of the distribution of contaminants within a given zone (i.e., room) to account for diffusion between zones and to allow for settling of simulated particulate contaminants. With these modifications, simulations have been performed of the release of chemical and biological warfare (CBW) agents in a building, which, in turn, allow for the determination of the optimal location of sensors to detect these releases. Multiple realizations of possible CBWbased terrorist attacks in this synthetic facility have been generated for the optimization of the placement of sensors installed for the earliest possible alert-time, using a genetic algorithm approach.

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, James W.; Emmerich, Steven J.; Walton, George N., Modeling the Performance of a Naturally Ventilated Commercial Building with a Multizone Coupled Thermal/Airflow Simulation Tool, National Institute of Standards and Technology, Gaithersburg, MD. ASHRAE Transactions 2002, V. 108, Pt. 2.; HI-02-21-4

Natural ventilation systems have long been employed in European residences to control indoor air quality and provide thermal comfort. Increasingly, European building designers have turned to natural ventilation to control air quality and cool commercial and institutional buildings as well, hoping to take advantage of the potential of natural ventilation systems to conserve energy associated with mechanical cooling and fan operation. Encouraged by the early successes of the past decade, European building designers have advanced natural ventilation technology, introduced promising hybrid ventilation technologies that combine mechanical and natural means, and developed analytical tools for the design of these systems. These systems may be adapted to the North American context, but much work will need to be done to realize the full potential natural ventilation may offer to North America. The needed work includes modeling studies that may require advanced simulation tools to adequately model the complex coupled thermal and airflow dynamics.

A modeling study of a representative naturally ventilated building recently constructed in The Netherlands is presented. A multizone coupled thermal/airflow simulation tool CONTAM97R is used to investigate the performance of this building in two challenging North American climates. Comparisons of measured and predicted performance of this building in its native climate were performed as a validation exercise and to calibrate the building models used for subsequent analytical studies. Initially, two models of a five-story segment of this building were formulated—a single-zone model with detailed representations of ventilation inlets and exhausts and a highly detailed 31-zone model accounting for all purpose-provided and infiltration flow paths.

After the calibration studies, a moderately detailed 11- zone model was then used to demonstrate the application of macroscopic coupled thermal/airflow performance evaluation to the design development of night ventilation cooling systems for the Enschede Tax Office placed in a hot, arid North American location—Los Angeles, California. Following a trial-and-error procedure using an overheated degree-hour performance metric, component sizes were adjusted to achieve the night cooling objective.

This modeling effort demonstrated that a macroscopic tool such as CONTAM97R provides essential spatial and temporal details that can guide system design relating to both whole-building and inter-room air distribution and thermal performance. In some cases, greater intra-room detail may be required. In these cases, performance evaluation would reasonably proceed to detailed computational fluid dynamic studies of individual rooms.

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, Steven J.; Gorfain, Joshua E.; Huang, Mike; Howard-Reed, Cynthia. Air and Pollutant Transport from Attached Garages to Residential LivingSpaces. National Institute of Standards and Technology, Gaithersburg, MD. December 2003

NIST is conducting a study on the indoor air quality (IAQ) impacts and engineering solutions related to the transport of pollutants from attached garages to residential living spaces. Natural or equipment-induced pressure differences across air leakage paths in house-garage (HG) interfaces can result in the transport of the contaminants generated in garages into adjacent living spaces. This paper summarizes a literature review on the transport of pollutants from garages to residential living spaces and describes a field study to estimate the range of airtightness of attached garages and of HG interfaces in a sample of U.S. homes.

Although the body of literature on pollutant transport from attached garages to residential buildings is limited, the studies reviewed provide substantial evidence that transport of contaminants from garages has the potential to negatively impact residential IAQ in either an acute (e.g., carbon monoxide from automobiles) or chronic manner (e.g., storage of chemical products). However, the literature contains more questions than answers on issues such as the airtightness and geometry of the HG interface, the impact of heating and cooling equipment in the garage, and the effectiveness of potential engineering solutions.

In order to address one gap in understanding these issues, the airtightness of garages and HG interfaces was measured in five residences using fan pressurization. While the small sample of houses limits generalization of the results, a range of house ages, styles, and sizes was included. For all homes tested, the garage was found to be at least twice as leaky as the house, based on air changes per hour at 50 Pa. The leakiness of the garage envelope, based on surface area normalized effective leakage area at 4 Pa (ELA4/SA), ranges from a high of nearly eleven times to a low of two and a half times that of the house exterior envelope leakage. On average, the HG interface was almost two and a half times leakier than the rest of the house envelope, when based on ELA4/SA. However, this average is somewhat skewed due to one HG interface measured in this study that is almost eleven times leakier than the rest of the house envelope. Conversely, a larger Canadian study found HG interfaces to be comparable to house envelopes but found the average garage to be about ten times leakier than the houses – possibly because Canadian houses are consistently tighter than U.S. houses (Fugler et al. 2002).

The knowledge gained from this review and the field study will be used in a simulation study of the potential occupant exposure to pollutants from attached garages and to explore potential engineering solutions to associated IAQ problems.

Emmerich, Steven J.; Persily, Andrew K.; Dols, W. Stuart; Axley, James W. Impact of Natural Ventilation Strategies and Design Issues for California Applications, Including Input to ASHRAE Standard 62 and California Title 24. National Institute of Standards and Technology, Gaithersburg, MD. October 2003

Natural ventilation has the potential to reduce the energy required for cooling and ventilating commercial buildings while still providing acceptable thermal comfort and indoor air quality. While a recent surge of interest in Europe has advanced natural ventilation technology, much work is needed to realize this potential in California and the rest of the U.S. This report discusses the impact of natural ventilation strategies and design issues for California applications and provides input to ASHRAE Standard 62 and California Title 24 based on research performed by NIST that has been previously reported (Emmerich et al. 2001 and Dols and Emmerich 2002), additional work completed recently by NIST for the California Energy Commission, other completed and ongoing research by NIST, and other recent published literature. One area identified as a key to the realization of the potential advantages of natural ventilation is the emergence of hybrid natural and mechanical system strategies. The report provides recommendations for additional research and technology transfer to further advance application of natural ventilation to commercial buildings.

Emmerich, Steven J.; Dols, W. Stuart. LoopDA: A Natural Ventilation System Design And Analysis Tool. National Institute of Standards and Technology, Gaithersburg, MD. Eighth Annual IBPSA Conference, Eindhoven, Nertherlands; August 11-14, 2003;

The Loop Equation Design Method has been proposed for sizing ventilation airflow components of natural and hybrid ventilation systems. While the loop design method has been demonstrated on a limited basis, the method has been automated in order to better evaluate its reliability under a more controlled, i.e., less error-prone, environment. This paper describes a computer program that implements the Loop Equation Design Method of sizing the openings of naturally ventilated buildings. The tool, referred to as LoopDA for Loop Design and Analysis, is integrated with the existing multi-zone IAQ model CONTAMW. LoopDA provides the designer of natural ventilation systems with an environment in which to perform and document the process of designing the opening sizes of natural ventilation systems and analyzing the system behavior under a variety of operating conditions. This paper describes the first version of the LoopDA program, provides an example of its application to the design of a naturally ventilated building and describes needs for future enhancements to the tool to increase its usefulness within the design community.

Emmerich, Steven J.; Nabinger, Steven J.; Gupte, Arpita; Howard-Reed, Cynthia; Wallace, Lance; Comparison of Measured and Predicted Tracer Gas Concentrations in a Townhouse National Institute of Standards and Technology, Gaithersburg, MD. National Exposure Research Laboratory, U.S. Environmental Protection Agency. NISTIR 7035, August 2003

To provide additional validation data for the multizone airflow and contaminant modeling approach (i.e., as implemented in the CONTAMW simulation program), a series of tracer gas tests were performed in an occupied three-story townhouse in Reston, Va. Tests simulated with CONTAMW consisted of short-term release of 1500 mL of tracer gas, sulfur hexaflouride (SF6), within one room of the house and the measurement of SF6 concentration in 10 indoor locations. In four of the ten main test cases, the heating and air-conditioning system fan was operating. In an eleventh test case, an attic fan was operating. The location of the burst source of tracer gas included the recreation room (basement level), the kitchen/dining room (main level) and the master bedroom (upstairs level). Experiments were conducted between May 2000 and June 2001. Local ambient conditions that ranged from a low outdoor temperature of 5 �C to a high of 29 �C and wind conditions that ranged from calm to moderate, with an average wind speed of 4 m/s, were measured and used as model inputs.

A statistical comparison of measurements and predictions was performed per ASTM Guide D5157 �Standard Guide for Statistical Evaluation of Indoor Air Quality Models� (ASTM 1997) for all cases. Guide D5157 provides statistical parameters to assess both agreement and bias and suggested criteria that model predictions should meet. Predicted and measured transient concentrations for individual zone and time-averaged zone concentrations for the whole house were compared for each test.

The results for zone average concentrations were very good with most cases meeting most or all of the D5157 criteria. For example, 9 of 10 cases met the normalized mean square error (NMSE) criteria and all cases met the normalized fractional bias (FB) criteria. Three cases did not meet the D5157 criteria for both correlation coefficient and line of regression but the discrepancy was due almost entirely to poor prediction in a single zone � the main floor bathroom. Excluding that zone resulted in these cases meeting or coming very close to meeting the D5157 criteria. For all cases, the predicted SF6 concentration averaged linearly over all zones was within 25 % of the average measured concentration.

Predictions of individual zone transient concentrations were less reliable. While many cases met all the criteria, nearly half of the cases failed to meet two or more of the D5157 criteria. One factor affecting the comparison of transient concentrations was significant differences between measured and predicted peak concentrations. This difficulty is not surprising as neither the simulations nor the experiments were designed to adequately account for very short-term peaks. The report also compares predicted and measured whole house air change rates and examines the effects of weather on those rates.

Emmerich, Steven J.; Nabinger, Steven J.; Gupte, Arpita; Howard-Reed, Cynthia; Validation of CONTAMW Predictions for Tracer Gas in a Townhouse National Institute of Standards and Technology, Gaithersburg, MD. IBPSA Conference, Eindhoven, Netherlands; August 11-14, 2003

To provide additional validation data for the multizone airflow and contaminant model, CONTAMW, experiments were performed in an occupied 3-story townhouse in Reston, VA. A tracer gas, sulfur hexaflouride (SF6), was manually injected within one room of the house and the concentration of SF6 was measured in each zone. This same process was then recreated in CONTAMW and the resulting predictions were statistically compared to the measured values. A total of 10 experiments were conducted and simulated between May 2000 and June 2001. The tests involved injecting 1500 mL of 1 % SF6 in a single room of the house. In 4 of the 10 cases, the heating and air-conditioning system fan was operating. SF6 was injected in the Recreation Room (basement level), the Kitchen/Dining Room (main level) and the Master Bedroom (upstairs level). Ambient conditions ranged from a low outdoor temperature of 5 �C to a high of 29 �C. Wind conditions ranged from calm to moderate with a high average wind speed of 4 m/s. A statistical comparison of measurements and predictions was performed per ASTM D5157 (ASTM 1997) for all cases. Comparisons were made for overall zone average concentrations and individual zone transient concentrations. The results for zone average concentrations were very good with many cases meeting most or all of the D5157 criteria. Several cases showed a poor to fair correlation between average measurements and predictions due to discrepancies with a single zone - the main floor bathroom - but excluding that zone resulted in these cases meeting or nearly meeting the D5157 criteria. Comparisons of individual zone transient concentrations were mixed with many good to excellent cases but also numerous fair to poor. As expected, there were frequently large differences between measured and predicted peak concentrations. Also, the bathroom zone was a consistently difficult zone to predict accurately. Other zones had occasional poor comparisons between predictions and measurements but no consistent discrepancies. The predicted SF6 concentration averaged over all zones and cases was within 10 % of the average measured concentration. Excluding the bathroom zone, the overall average predicted concentration (115 �g/m3) was essentially identical to the overall average measured concentration (116 �g/m3).

Emmerich, Steven J., Validation of Multizone IAQ Modeling of Residential-Scale Buildings: A Review National Institute of Standards and Technology, Gaithersburg, MD. ASHRAE Transactions 2001, V. 107, Pt. 2. CI-01-8-1;

This paper reviews empirical validation studies of the application of multizone indoor air quality (IAQ) models to residential-scale buildings. This review focuses on empirical verification efforts, although models have also been subjected to analytical verification and inter-model comparisons. In most reports, experimental data were compared to predictions of only one model � typically, either the CONTAM or COMIS models. However, inter-model comparisons have demonstrated consistency between these and other multizone models so most comparisons can be generalized to all multizone models. Few of the empirical verifications reported statistical analyses of the comparison between measurements and predictions. Where sufficient data were available in the literature, additional statistical analyses have been performed and reported.Also, most published reports did not address the issue of measurement uncertainty. No single reportedmultizone IAQ model validation effort can be considered to be complete due to limitations in scope, inadequate detail describing experimental and/or modeling procedures, lack of rigorous statistical analysis, inclusion of only small ranges of airflows and concentrations, questions on independence of validation datasets, and other shortcomings. However, if one considers the body of published validation work, it may be concluded that a knowledgeable user can expect to make reasonable predictions of air change rates, interzonal flows, and contaminant concentrations for residential- scale buildings dominated by stack-driven or ventilation flows with inert pollutants. In contrast, more work is clearly needed for applications with high wind speeds, reactive contaminants, or specialized situations such as ambient pollutant entry, small time scales, and non-trace contaminants. Additionally, future model validation efforts will be more useful if more statistical analyses are performed and if more detail on both the measurements and modeling are reported.

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.

Emmerich, Steven J; Persily, Andrew K; Effectiveness of a Heat Recovery Ventilator, an Outdoor Air Intake Damper and an Electrostatic Particulate Filter at Controlling Indoor Air Quality in Residential Buildings National Institute of Standards and Technology, Gaithersburg, MD. 16th AIVC Conference, Palm Springs, USA 19-22 September, 1995

A preliminary study of the potential for using central forced-air heating and cooling system modifications to control indoor air quality (IAQ) in residential buildings was performed. The main objective was to provide insight into the potential of three IAQ control options to mitigate residential IAQ problems, the pollutant sources the controls are most likely to impact, and the potential limitations of the controls. Another important objective was to identifi key issues related to the use of multizone models to study residential IAQ and to identi~ areas for follow-up work. The muhizone airflow and pollutimt transport program CONTAM93 (-1]was used to simulate pollutant concentrations due to a variety of sources in eight houses with typical HVAC systems under different weather conditions. The simulations were repeated after modifying the systems with three IAQ control technologies - an electrostatic particulate filter, a heat recovery ventilator (HRV), and an outdoor air intake damper (OAID) on the forced-air system return, Although the system modifications reduced pollutant concentrations in the houses for some cases, the HRV and OAJD increased pollutant concentrations in certain situations involving a combination of weak indoor sources, high outdoor concentrations, and indoor pollutant removal mechanisms. Also, limited system run-time during mild weather was identified as a limitation of IAQ controls that operate in conjunction with forced-air systems. Recommendations for future research include: simulation of other buildings, pollutants, and LAQcontrol technologies; model validation; sensitivity analysis; and development of a database of important model inputs.

Eriksson, Jorgen; Asa Wahlstrom, Ph.D., Use of Multizone Air Exchange Simulation to Evaluate a Hybrid Ventilation System 2002, ASHRAE Annual Meeting

This paper describes how a multizone air exchange simulation program has been used to evaluate the performance of a hybrid ventilation system in a Swedish school building. To increase the buoyancy effect, the school was equipped with a solar chimney. Since a low-pressure ventilation system, such as a hybrid ventilation system, may be very sensitive to wind speed, wind direction, and temperature changes, it is important to evaluate the performance of the system for different conditions. First, the sensitivity of the system to changes in the wind conditions was evaluated. The second analysis was to study if the air is transported between the different zones or if all air follows the path designed. Here, a number of combinations of opened and closed doors were tested. In addition, during this analysis different damper authorities were tested. The third analysis evaluated the performance of the solar chimney.

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.

 

Ferreira, 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.

 

Ferreira, Michael J., P.E. Use of Multizone Modeling for High-Rise Smoke Control System Design. 2002, ASHRAE Annual Meeting

This paper provides an overview of the use of the CONTAM building airflow and contaminant dispersal model for the design of smoke control systems in high-rise buildings. The Uniform Building Code and the International Building Code require that the impact of various forces affecting building smoke control, including wind, stack effects, variation of openings, and HVAC configurations, be considered in the design of smoke control systems. Building airflow models such as CONTAM are well suited to this application. The paper will discuss limitations of the CONTAM network model for modeling buoyant smoke and how to overcome these limitations. Finally, the paper will discuss issues pertaining to the use of CONTAM for designing smoke control systems in high-rise office and residential buildings.

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

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.

Howard-Reed, Cynthia; Wallace, Lance A.; Emmerich Steven J., Deposition Rates of Fine and CoarseParticles in Residential Buildings: Literature Review and Measurementsin an Occupied Townhouse. National Institute of Standards and Technology, Gaithersburg, MD. MD. US Environmental Protection Agency, Reston, VA. October 2003.

Several studies have shown the importance of particle losses in real homes due to deposition and filtration; however, none have quantitatively shown the impact of using a central forced air fan and in-duct filter on particle loss rates. In an attempt to provide such data, we measured the deposition of fine and coarse particles following specific source events in an occupied townhouse and also in an unoccupied test house. Experiments were run with three different sources (cooking with a gas stove, citronella candle, pouring kitty litter), with the central heating and air conditioning (HAC) fan on or off, and with two different types of in-duct filters (electrostatic precipitator and ordinary furnace filter). These tests resulted in a database of deposition rates for particles ranging from 0.3 µm to 10 µm under a wide range of occupancy conditions. Particle size, HAC fan operation, and the electrostatic precipitator had significant effects on particle loss rates. The standard furnace filter had no effect on loss rates. Surprisingly, the type of source (combustion vs. mechanical generation) and the type of furnishings (fully furnished including carpet vs. largely unfurnished including mostly bare floor) also had no measurable effect on the deposition rates of particles of comparable size. With the HAC fan off, average deposition rates varied from 0.3 h^-1 for the smallest particle range (0.3 µm to 0.5 µm) to 5.2 h^-1 for particles greater than 10 µm. Operation of the central HAC fan approximately doubled these rates for particles < 5 µm, and increased rates by 2 h^-1 for the larger particles. An in-duct electrostatic precipitator increased the loss rates compared to the fan-off condition by factors of 5 to 10 for particles < 2.5 µm, and by a factor of 3 for the larger particles.

Howard-Reed, Cynthia; Wallace, Lance A.; Emmerich Steven J., Effect of ventilation systems and air fifilters on decay rates of particles produced by indoor sources in an occupied townhouse. National Institute of Standards and Technology, Gaithersburg, MD. MD. US Environmental Protection Agency, Reston, VA. 4 September 2003.

Several studies have shown the importance of particle losses in real homes due to deposition and fifiltration; however, none have quantitatively shown the impact of using a central forced air fan and in-duct fifilter on particle loss rates. In an attempt to provide such data, we measured the deposition of particles ranging from 0.3 to 10 µm in an occupied townhouse and also in an unoccupied test house. Experiments were run with three different sources (cooking with a gas stove, citronella candle, pouring kitty litter), with the central heating and air conditioning (HAC) fan on or off, and with two different types of in-duct fifilters (electrostatic precipitator and ordinary furnace fifilter). Particle size, HAC fan operation, and the electrostatic precipitator had significant effects on particle loss rates. The standard furnace fifilter had no effect. Surprisingly, the type of source (combustion vs. mechanical generation) and the type of furnishings (fully furnished including carpet vs. largely unfurnished including mostly bare flfloor) also had no measurable effect on the deposition rates of particles of comparable size. With the HAC fan off, average deposition rates varied from 0.3 h^-1 for the smallest particle range (0.3–0.5 µm) to 5.2 h^-1 for particles greater than 10 µm. Operation of the central HAC fan approximately doubled these rates for particles <5 µm, and increased rates by 2 h^-1 for the larger particles. An in-duct electrostatic precipitator increased the loss rates compared to the fan-off condition by factors of 5–10 for particles <2.5 µm, and by a factor of 3 for 2.5–5.0 µm particles. In practical terms, use of the central fan alone could reduce indoor particle concentrations by 25–50%, and use of an in-duct ESP could reduce particle concentrations by 55–85% compared to fan-off conditions.

Howard-Reed, Cynthia ; Polidoro, Brian; and Dols, W. Stuart, Development of IAQ Model Input Databases: Volatile Organic Compound Source Emission Rates. National Institute of Standards and Technology, Gaithersburg, MD. 2003.

Indoor air quality (IAQ) models can be used to predict airflows, contaminant concentrations and personal exposures for a given indoor environment. In order to generate such results, these models require the user to provide a wide range of input data including envelope leakage information, weather, ventilation system characteristics, contaminant source emission rates, sink removal rates, occupant schedules, and air cleaner removal rates. Many of the required data are available in the literature; however, this information has generally not been compiled in a convenient form for use in an IAQ model. As a result, finding appropriate model data can be a repetitive and laborious process for the user.

To make this effort more efficient, the National Institute of Standards and Technology (NIST) has begun an effort to compile model input data needs into searchable databases. The process involves collecting data from the literature, designing a database format to standardize data entry, entering the information into the database, and developing a computer program to search the database for specific records to use in an IAQ model. This process has been completed for airflow leakage elements, wind pressure coefficients, and ventilation system schedules and is currently underway for VOC source emission rates. With these databases, CONTAMW users and other modelers will be able to simulate a wide range of exposure scenarios in different types of buildings as well as simulate the impacts of potential control strategies. In addition, as a result of this work, it will be possible to identify important gaps in the data.

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