IAQ Models of Representative U.S. Homes

Residential exposure analysis with CONTAM

Andrew PersilyNational Institute of Standards and

TechnologyGaithersburg, MD

andyp@nist.gov, 301 975-6418

NSF/UL 440 Environments & Products TeleconferenceMay 24, 2012

Topics for Today

• IAQ modeling with CONTAM

• “Suite of homes” CONTAM models of US dwellings

• Issues in modeling exposure

Building Airflow and Contaminant Transport Modeling

Macroscopic/MultizoneNetwork airflow analysis

Each zone: 1 node, 1 reference pressure, uniform temperature & concentration

e.g., CONTAM

Microscopic/CFDDetails of airflow and contaminant concentrations in a space

e.g., FDS, FLUENT, CFD0

CONTAM www.bfrl.nist.gov/IAQanalysis

CONTAM SketchPad

CONTAMW Inputs & OutputsEnvironmental FactorsWind Speed and DirectionWind Pressure CoefficientIndoor/Outdoor TempOutdoor Contaminants

FiltrationSteady State SimulationScheduled Flows, Sources

etc.Transient Simulations up to

One YearFirst Order Chemical

ReactionsData Libraries

Building and System DescriptionBuilding Zone ConfigurationBuilding Leakage CharacteristicsHVAC Airflow RatesDuct SystemsFilter Efficiencies

Contaminant InformationChemical Reaction DataContaminant Sink CharacteristicsContaminant Source StrengthOccupancy Schedules

Infiltration Rates

Interzonal Airflows

Pressure Drops across Openings

Contaminant

Concentrations

Exposure Levels

NIST “Suite of Homes”

HUD-funded effort to define a representative collection of houses based on U.S. building surveys (e.g., Census, DOE)– 209 dwellings that represent 80 % of the U.S. housing stock

Floor plans and CONTAM models available for

download

Variables used to define dwellings

Suite of Homes

Persily et al. 2006. A Collection of Homes to Representthe U.S. Housing Stock, NIST report NISTIR 7330.

Report, CONTAM files and floor plans: http://www.bfrl.nist.gov/IAQanalysis/case%20studies/cwcase_11.htm

Application “Suite of Homes”First statistically representative distribution of ventilation rates in U.S. homes

CONTAM models are being used for IAQ and exposure studies

Advantages: Established and documented; public domain; generates distribution instead of single value

Indoor CO exposure from emergency generatorsPersily et al. 2010. Indoor

Air. 20: 473-485.

Issues in modeling exposureBASIC QUESTIONSHow many dwellings: Which and why?Simulation duration: 24 h? Annual?Occupants: Number? Schedule?Contaminants: How many?

INPUTSWeather conditions: How many?Building tightness: Covered in suite modelsMechanical ventilation: Any? How much?Impose constant air change rate or calculate from leakage/weather?

Source strengths: Source areasRemoval mechanisms: Surface sorption? Air cleaning?

DATA MANAGEMENT AND ANALYSIS