TOUR OF NIST MANUFACTURED RESEARCH HOUSE Andy Persily, Steve Nabinger, Steve Emmerich, Cindy Howard Reed Building and Fire Research Laboratory National.

TOUR OF NIST MANUFACTURED RESEARCH HOUSE

Andy Persily, Steve Nabinger, Steve Emmerich, Cindy Howard Reed

Building and Fire Research LaboratoryNational Institute of Standards and Technology

Michael LublinerWashington 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. MartinBuilding and Fire Research Laboratory

National Institute of Standards and TechnologyGaithersburg, 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 RequirementsMinimum 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 standardOutdoor 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 returnWhole 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, forced-

air 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

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

-20 -10 0 10 20 30 40 50

Indoor-outdoor temperature difference (°C)

Air Change Rate (h

-1)

SAMPLE RESULTS (Albany)

Simulation conditions Mean air change

rate (h-1)

% of hours < 0. 35 h-1

Effective air change rate (h-1)

Envelope leakage and scheduled exhaust fans

0.27 77 0.17

Forced-air inlet; operating on outside temperature

0.37 46 0.19

Forced-air inlet operating during occupancy

0.59 18 0.34

Passive inlets: whole house exhaust on limited schedule

0.41 42 0.24

Passive inlets: whole house exhaust on during occupancy

0.50 29 0.34

ENERGY CONSUMPTION (Albany)

Simulation conditionsAnnual Energy Use MJ (kWh)

Heating, Cooling and Fans

No “mechanical ventilation”; ductleakage and exhaust only

18459 (5128)

Forced-air inlet; operating on Tout 20140 (5595)

Forced-air inlet operating duringoccupancy

31339 (8706)

Passive inlets: whole house exhaustoperating on limited schedule

21217 (5894)

Passive inlets: whole house exhaustoperating during occupancy

24646 (6846)

Constant air change rate; 0.35 h-1 14970 (4159)

CONCLUSIONS0.25 h-1 assumption for infiltration

Ignores weather; < 0.25 h-1 for much of the year

Outdoor air inlet on furnace returnProvides 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 ventsSufficient ventilation and good distribution, but

depends on operation; potential for under- and over-ventilation; 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 HOUSEDelivery and installation, January 2002

NIST RESEARCH HOUSE

Installation of instrumentation, Spring 2002

Initial testing

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 HOUSECrawl space

CONTAM MODELS OF HOUSE

Living area

SYSTEM AIRFLOWS (preliminary)Measured and predicted with CONTAM

Measured(cfm)

Predicted(cfm)

Sum of supply registers 736 736Supply leak into crawl space -- 197Total flow through fan 942 933

Return grille 925 918

Outdoor air intake 16 16

EXHAUST AND INTAKE AIRFLOWS (preliminary)

Design and measured values

Required(cfm)

Measured(cfm)

Kitchen exhaust 100 47Bath exhaust #2 50 20Master bath exhaust 50 20Whole house exhaust 53 20

Outdoor air intake 53 16

INDOOR VOC LEVELS (preliminary)

503

400

450

500

550

600

650

700

750

800

08/09 00:00 08/10 00:00 08/11 00:00 08/12 00:00 08/13 00:00 08/14 00:00

Date & Time

Concentration (ug/m3)

0

10

20

30

40

50

60

70

80

Temperature (C)

TVOC Temp_IN Temp_OUT Temp_CRAWL

RESEARCH PLANS Complete initial characterization, fall ‘02 Air change rates under different operating modes

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

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