Transcript PANEL 98 - ba-pirc

TOUR OF NIST MANUFACTURED
RESEARCH HOUSE
Andy Persily, Steve Nabinger, Steve Emmerich,
Cindy Howard Reed
Building and Fire Research Laboratory
National Institute of Standards and Technology
Michael Lubliner
Washington State University
October 2, 2002
SCHEDULE FOR MORNING
• Background on NIST manufactured house
ventilation and IAQ research
– NIST Modeling study for HUD
• Mike Lubliner on DOE/EPA/HUD activities
• Tour of research house
A MODELING STUDY OF VENTILATION
IN MANUFACTURED HOUSES
Andrew K. Persily, Samuel R. Martin
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, Maryland USA
ASHRAE/BETEC/CIBSE/ORNL/DOE/NRCC Performance of
Exterior Envelopes of Whole Buildings VIII
December 2001
Funded by US Dept of Housing and Urban Development
BACKGROUND
US manufactured homes built to HUD Manufactured
Homes Construction and Safety Standards
MHCSS Requirements
Minimum air change rate of 0.35 h-1
Mechanical or passive system to provide 0.1 h-1
(assumes infiltration rate of 0.25 h-1)
Variety of systems being used to meet standard
Outdoor air intake on forced-air furnace return
Whole house exhaust fan with or without inlet vents
STUDY QUESTIONS
Validity of 0.25 h-1 assumption for infiltration
Ventilation rates, air distribution and energy use of
systems being used to meet the MHCSS standard:
Outdoor air inlet on furnace return
Whole house exhaust fan with passive inlet vents
Whole house exhaust fan without passive inlet vents
SIMULATION APPROACH
CONTAM multizone airflow model:
Exterior envelope leakage, interior partitions, forcedair distribution and duct leakage, exhaust fan
operation, and outdoor weather
Steady-state airflow simulations for different systems
Annual simulations for different systems: Miami
(hot/humid), Albany (cold/mixed), Seattle (temperate)
Albany: Forced-air intake controlled by heating & cooling demand
SAMPLE RESULTS (Albany)
Simulation conditions
Mean air
change
rate (h-1)
Envelope leakage and scheduled
0.27
exhaust fans
Forced-air inlet; operating on
0.37
outside temperature
Forced-air inlet operating
0.59
during occupancy
Passive inlets: whole house
0.41
exhaust on limited schedule
Passive inlets: whole house
0.50
exhaust on during occupancy
% of
hours <
0. 35 h-1
77
Effective
air change
rate (h-1)
0.17
46
0.19
18
0.34
42
0.24
29
0.34
ENERGY CONSUMPTION (Albany)
Simulation conditions
No Òmechanical ventilationÓ; duct
leakage and exhaust only
Annual Energy Use MJ (kWh)
Heating, Cooling and Fans
18459 (5128)
Forced-air inlet; operating on Tout
20140 (5595)
Forced-air inlet operating during
occupancy
31339 (8706)
Passive inlets: whole house exhaust
operating on limited schedule
21217 (5894)
Passive inlets: whole house exhaust
operating during occupancy
24646 (6846)
Constant air change rate; 0.35 h-1
14970 (4159)
CONCLUSIONS
0.25 h-1 assumption for infiltration
Ignores weather; < 0.25 h-1 for much of the year
Outdoor air inlet on furnace return
Provides sufficient ventilation and good distribution,
but impact depends on operating strategy; potential
for both under- and over-ventilation
Whole house exhaust fan with passive inlet vents
Sufficient ventilation and good distribution, but
depends on operation; potential for under- and overventilation; make more sense in tight buildings
RECOMMENDATIONS
Modify infiltration assumption in standard to
account for weather-induced variation
Standards need to address operation of mechanical
ventilation systems
“Optimize” by tightening ducts and building
envelope, then assess systems
Verify findings through field studies
Investigate pollutant impacts of ventilation
NIST RESEARCH HOUSE
Delivery and installation, January 2002
NIST RESEARCH HOUSE
Initial testing
Installation of instrumentation,
Spring 2002
RESULTS TO DATE (preliminary)
•Airtightness
–Whole building blower door: 9.1 h-1 at 50 Pa, ELA at 4 Pa = 103 in2
–Duct leakage: 225 cfm at 25 Pa
•Tracer gas measurements of air change rate
–Forced-air fan off: 0.1 - 0.2 h-1 (summer)
–Forced-air fan on, intake closed: 0.4 - 0.5 h-1 (summer)
–Forced-air fan on, intake open: 0.4 - 0.6 h-1 (summer)
•Initial VOC concentrations and emissions
•Initial relative humidity levels and removal by AC
CONTAM MODELS OF HOUSE
Crawl space
CONTAM MODELS OF HOUSE
Living area
SYSTEM AIRFLOWS (preliminary)
Measured and predicted with CONTAM
Measured Predicted
(cfm)
(cfm)
Sum of supply registers
Supply leak into crawl space
Total flow through fan
736
-942
736
197
933
Return grille
925
918
Outdoor air intake
16
16
EXHAUST AND INTAKE AIRFLOWS
(preliminary)
Design and measured values
Required Measured
(cfm)
(cfm)
Kitchen exhaust
Bath exhaust #2
Master bath exhaust
Whole house exhaust
100
50
50
53
47
20
20
20
Outdoor air intake
53
16
INDOOR VOC LEVELS (preliminary)
RESEARCH PLANS
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Complete initial characterization, fall ‘02
Air change rates under different operating modes
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Fans off, infiltration only
Forced-air operating on thermostat, with intake open/sealed
Forced-air operating, bath & kitchen exhaust fans on schedule
Forced-air operating, whole house exhaust, window vents open/sealed
Compare measured and predicted (CONTAM) air
change rates
Characterization of humidity performance, water
vapor storage in materials and furnishings
Performance of gaseous air cleaners
VOC/formaldehyde emissions over time (LBNL)
LONGER TERM RESEARCH
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Retrofit
First stage, could have been done at little cost
Address envelope and duct leakage
Second stage, more advanced and cost
Replace forced-air system
Efficient whole house exhaust
Details studies of moisture: sources, transport and
ventilation
Emissions from combustion appliances