A detailed model is developed for predicting the ventilation rates of the indoor, conditioned zone of a house and the attic zone. The complete set of algorithms is presented in a form for direct incorporation in a two zone ventilation model. One of the important predictions from this model is the leakage flow rate between the indoor and attic zones. Ventilation rates are predicted from a steady state mass flow rate balance for each zone where all individual flow rates through leakage sites are based on a power law expression for flow rate versus pressure difference. The envelope leakage includes distributed leakage associated with background leakage, localized leakage associated with vents and flues, and active fan ventilation. The predicted ventilation rates agree quite well with field measurements of ventilation rates in houses and attics with different leakage configurations, without the use of any empirically adjusted parameters or constants.

1 aWalker, Iain, S.1 aForest, Tom, W.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/attic-interior-infiltration-and01538nas a2200169 4500008004100000245013500041210006900176300001200245490000700257520091400264100002401178700002201202700002001224700002301244700002401267856007701291 2003 eng d00aPollutant Dispersion in a Large Indoor Space: Part 1 -- Scaled experiments using a water-filled model with occupants and furniture0 aPollutant Dispersion in a Large Indoor Space Part 1 Scaled exper a258-2710 v143 aPollutant dispersion experiments were performed in a water-filled 30:1 scale model of a large room. Theoretical calculations were performed to confirm that the effects from losses of molecular diffusion, small scale eddies, turbulent kinetic energy, and turbulent mass diffusivity were minimal, even without matching Reynolds number between model and full scale. In the experiments, uranine dye was injected continuously from a small point source near the floor of the model. Pollutant concentrations were measured in a plane using laser induced fluorescence techniques. The concentration profiles were measured for three interior configurations for the model: unobstructed, table-like obstructions, and table- like and figure-like obstructions. The presence of objects in the model interior had a significant effect of both the concentration profile and fluctuation intensity in the measurement plane.

1 aThatcher, Tracy, L.1 aWilson, David, J.1 aWood, Emily, E.1 aCraig, Mathias, J.1 aSextro, Richard, G. uhttps://buildings.lbl.gov/publications/pollutant-dispersion-large-indoor01147nas a2200145 4500008004100000245009500041210006900136300001200205490000700217520063900224100002100863700002200884700002100906856007400927 1998 eng d00aA Comparison of the Power Law to Quadratic Formulations for Air Infiltration Calculations0 aComparison of the Power Law to Quadratic Formulations for Air In a293-2990 v273 aAlthough the power law has been broadly accepted in measurement and air infiltration standards, and in many air infiltration calculation methods, the assumption that the power law is true over the range of pressures that a building envelope experiences has not been well documented. In this paper, we examine the validity of the power law through theoretical analysis, laboratory measurements of crack flow and detailed field tests of building envelopes. The results of the theoretical considerations, and field and laboratory measurements indicate that the power law is valid for low pressure building envelope leakage.

1 aWalker, Iain, S.1 aWilson, David, J.1 aSherman, Max, H. uhttps://buildings.lbl.gov/publications/comparison-power-law-quadratic01666nas a2200133 4500008004100000245010000041210006900141300001200210490000600222520118100228100002101409700002201430856008001452 1998 eng d00aField Validation of Algebraic Equations for Stack and Wind Driven Air Infiltration Calculations0 aField Validation of Algebraic Equations for Stack and Wind Drive a119-1390 v43 aExplicit algebraic equations for calculation of wind and stack driven ventilation were developed by parametrically matching exact solutions to the flow equations for building envelopes. These separate wind and stack effect flow calculation procedures were incorporated in a simple natural ventilation model, AIM- 2, with empirical functions for superposition of wind and stack effect and for estimating wind shelter. The major improvements over previous simplified ventilation calculations are: a power law pressure-flow relationship is used to develop the flow equations form first principles, the furnace or fireplace flue is included as a separate leakage site and the model differentiates between houses with basements (or slab-on- grade) and crawlspaces. Over 3400 hours of measured ventilation rates from the test houses at the Alberta Home Heating Research Facility were used to validate the predictions of ventilation rates and to compare the AIM-2 predictions to those of other ventilation models. The AIM-2 model had bias and scatter errors of less than 15% for wind-dominated ventilation, and less than 7% for buoyancy ("stack-effect") dominated cases.1 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/field-validation-algebraic-equations00487nas a2200133 4500008004100000245009000041210006900131260001200200300001200212490000600224100002100230700002200251856008000273 1998 eng d00aField Validation of Equations for Stack and Wind Driven Air Infiltration Calculations0 aField Validation of Equations for Stack and Wind Driven Air Infi c04/1998 a119-1400 v41 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/field-validation-equations-stack-and01678nas a2200145 4500008004100000245007600041210006900117300001200186490000600198520118700204100002101391700002201412700002001434856007801454 1996 eng d00aA Wind Shadow Model for Air Infiltration Sheltering by Upwind Obstacles0 aWind Shadow Model for Air Infiltration Sheltering by Upwind Obst a265-2830 v23 aThe wind shadow model has been developed to calculate the wind sheltering effects of upwind obstacles for air infiltration calculations. This effect must be determined for infiltration calculations because, in almost all situations, only the unobstructed mean wind speed is known for a building site. This model has adapted the theoretical calculation procedures developed for far wake centreline velocity deficit calculations to near field flows, where shelter has a significant effect. The model uses the concept of a wind shadow projected downstream by upwind buildings to determine the effect of wake velocity reduction on building surfaces. The turbulent nature of the wake is accounted for by "flapping" the wake over a range of wind directions. The effectiveness of this model in accounting for sheltering effects in infiltration calculations has been examined by comparing infiltration model predictions including the wind shadow model to measured data from a row of test houses. The measured data covered a wide range of wind speeds, wind directions and leakage distributions by using over five thousand hours of infiltration measurements from five houses.1 aWalker, Iain, S.1 aWilson, David, J.1 aForest, Tom, W. uhttps://buildings.lbl.gov/publications/wind-shadow-model-air-infiltration01814nas a2200157 4500008004100000245006000041210005800101260009400159300001200253490000600265520124700271100002101518700002001539700002201559856007501581 1995 eng d00aA Simple Calculation Method for Attic Ventilation Rates0 aSimple Calculation Method for Attic Ventilation Rates aCoventry, Great BritainbAir Infiltration and Ventilation Centre, Coventry, Great Britain a221-2320 v13 aThe ventilation of an attic is critical in estimating heating and cooling loads for buildings because the air temperature in the attic is highly sensitive to ventilation rate. In addition, attic ventilation is an important parameter for determining moisture accumulation in attic spaces that can lead to structural damage and reduced insulation effectiveness. Historically, attic venting has been a common method for controlling attic temperature and moisture, but there have been no calculation techniques available to determine attic ventilation rates. Current practice is to use rules of thumb for estimating attic vent areas. Simple algebraic relationships are developed here, using functions fitted to an exact numerical solution for air flow through attic envelopes. This algebraic model (AVENT) was developed to be easy to use as diagnostic or design tool. Key factors included in the model are: climate (wind and stack effect), wind shelter, leakage distribution and total attic leakage. This paper validates the model predictions by comparing to measured data from two attics at the Alberta Home Heating Research Facility (AHHRF). Average errors for the model are about 15% compared to the measured ventilation rates.1 aWalker, Iain, S.1 aForest, Tom, W.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/simple-calculation-method-attic00521nas a2200133 4500008004100000245007500041210006900116260006000185300001200245490000600257100002100263700002200284856008100306 1994 eng d00aPractical Methods for Improving Estimates of Natural Ventilation Rates0 aPractical Methods for Improving Estimates of Natural Ventilation aCoventry, U.K.bAir Infiltration and Ventilation Centre a517-5260 v11 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/practical-methods-improving-estimates00481nas a2200133 4500008004100000245008600041210006900127260000900196300001200205490000700217100002100224700002200245856008000267 1993 eng d00aEvaluating Models for Superposition of Wind and Stack Effects in Air Infiltration0 aEvaluating Models for Superposition of Wind and Stack Effects in c1993 a201-2100 v281 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/evaluating-models-superposition-wind00395nas a2200097 4500008004100000245007000041210006900111100002200180700002100202856007400223 1993 eng d00aInfiltration Data From the Alberta Home Heating Research Facility0 aInfiltration Data From the Alberta Home Heating Research Facilit1 aWilson, David, J.1 aWalker, Iain, S. uhttps://buildings.lbl.gov/publications/infiltration-data-alberta-home00472nas a2200109 4500008004100000245010300041210006900144260003100213100002200244700002100266856007500287 1992 eng d00aFeasibility of Passive Ventilation by Constant Area Vents to Maintain Indoor Air Quality in Houses0 aFeasibility of Passive Ventilation by Constant Area Vents to Mai aSan Francisco, CAc10/19921 aWilson, David, J.1 aWalker, Iain, S. uhttps://buildings.lbl.gov/publications/feasibility-passive-ventilation00446nas a2200109 4500008004100000245005500041210005500096260006300151100002200214700002100236856007900257 1991 eng d00aPassive Ventilation to Maintain Indoor Air Quality0 aPassive Ventilation to Maintain Indoor Air Quality bUniversity of Alberta Department of Mechanical Engineering1 aWilson, David, J.1 aWalker, Iain, S. uhttps://buildings.lbl.gov/publications/passive-ventilation-maintain-indoor00470nas a2200133 4500008004100000245004500041210004500086260006900131300001200200490000600212100002200218700002100240856007500261 1991 eng d00aWind Shelter Effects for a Row of Houses0 aWind Shelter Effects for a Row of Houses aOttawa, Ontario, CanadabAir Infiltration and Ventilation Centre a335-3460 v11 aWilson, David, J.1 aWalker, Iain, S. uhttps://buildings.lbl.gov/publications/wind-shelter-effects-row-houses00424nas a2200109 4500008004100000245004400041210003700085260007300122100002100195700002200216856007600238 1990 eng d00aThe Alberta Infiltration Model, AIM - 20 aAlberta Infiltration Model AIM 2 aEdmontonbUniversity of Alberta Department of Mechanical Engineering1 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/alberta-infiltration-model-aim-200443nas a2200121 4500008004100000245005500041210005500096260004100151300001200192100002200204700002100226856007400247 1990 eng d00aCombining Air Infiltration and Exhaust Ventilation0 aCombining Air Infiltration and Exhaust Ventilation aToronto, CanadabIndoor Airc07/1990 a467-4721 aWilson, David, J.1 aWalker, Iain, S. uhttps://buildings.lbl.gov/publications/combining-air-infiltration-and00421nas a2200109 4500008004100000245007000041210006900111490000700180100002100187700002200208856008100230 1990 eng d00aIncluding Furnace Flue Leakage in a Simple Air Infiltration Model0 aIncluding Furnace Flue Leakage in a Simple Air Infiltration Mode0 v111 aWalker, Iain, S.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/including-furnace-flue-leakage-simple00469nas a2200133 4500008004100000245008100041210006900122260000900191300001200200490000700212100002100219700002200240856007300262 1986 eng d00aRelating Actual and Effective Ventilation in Determining In-door Air Quality0 aRelating Actual and Effective Ventilation in Determining Indoor c1986 a135-1440 v211 aSherman, Max, H.1 aWilson, David, J. uhttps://buildings.lbl.gov/publications/relating-actual-and-effective00445nas a2200145 4500008004100000245004300041210004300084260000900127300001200136490001200148100002100160700002200181700001700203856007900220 1986 eng d00aVariability in Residential Air Leakage0 aVariability in Residential Air Leakage c1986 a348-3640 vSTP:9041 aSherman, Max, H.1 aWilson, David, J.1 aKiel, Darwin uhttps://buildings.lbl.gov/publications/variability-residential-air-leakage01104nas a2200145 4500008004100000245006500041210006500106260000900171490000700180520063000187100001700817700002200834700002100856856008100877 1985 eng d00aAir Leakage Flow Correlations for Varying House Construction0 aAir Leakage Flow Correlations for Varying House Construction c19850 v913 aFan pressurization techniques are being employed by an increasingly large number of contractors

and auditors to determine the leakage characteristics of structures. In this study, a large

data base of flow exponents and flow coefficients are compiled to determine the degree of

correlation that exists between flow parameters. The resulting empirical relationships are

then used to determine the feasibility of predicting these flow parameters directly from a

single pressure difference test. On the basis of these correlations, a new pressure

independent tigh~ness parameter is proposed.