Modeling Study of Ventilation in Manufactured Houses.
Modeling Study of Ventilation in Manufactured Houses.
(7991 K)
Persily, A. K.; Martin, S. R.
NISTIR 6455; 87 p. February 2000.
Sponsor:
Department of Housing and Urban Development, Washington,
DC
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB2000-100623
Keywords:
manufactured housing; predictive models; ventilation;
residential buildings; air flow; air tightness; windows;
standards
Abstract:
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899