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Infiltration-pressurization correlation: Simplified physical modeling
Abstract and Figures
A model is presented for predicting air infiltration that eliminates many site-specific parameters normally required. The only information necessary is the geometry and leakage of the structure. The leakage quantities, expressed in terms of effective areas, are total leakage area and the leakage areas of the floor and ceiling. Weather parameters are mean wind speed, terrain class, and average temperature difference. The model separates the infiltration problem into two distinct parts: stack and wind-regimes. Each regime is treated independently; the transition between them is sharp. The model has been tested with data from several sites, differing in climate and construction methods.
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... • ZoneInfiltration:EffectiveLeakageArea (referred to as ELA, is based on an ASTM Standard E779 effective leakage area calculation [23]. Sherman and Grimsrud developed correlations for small detached residential buildings [24]): ...
Model calibration refines design-stage inputs to align with real-world building performance. Accurate parameter selection, especially for highly sensitive variables like air leakage, is crucial. This study compared two building energy model calibration methods. The “classic” method adjusted indoor air capacitance, internal mass, and air infiltration, while a novel method focused on capacitance and internal mass, using empirical data for infiltration. The infiltration values were calculated using the decay equation and the EnergyPlus equations with site-specific coefficients. A triple validation assessed model performance in terms of temperature (CIBSE TM63), energy consumption (minimization), and indoor air quality (represented by CO2 levels in accordance with the ASTM D5157 Standard). Results demonstrated the novel method’s superiority across all three performance metrics. All calibrated models met the CIBSE TM63 criteria even during the validation period, which was five times longer than the training period. Compared to the classic method, models incorporating dynamic empirical infiltration showed a 29% and 26% improvement in MAE and RMSE, respectively, in temperature prediction. In energy consumption results, the novel method models presented a 31% reduction, and for CO2 level agreement, these models achieved a 130% higher R² value than the classic model. In addition, the classic method’s infiltration values failed to meet ASTM D5157 requirements, suggesting reliance on unrealistic parameter values for accurate temperature representation. The incorporation of calculated air leakage data into the BEM allowed a more realistic estimation of capacitance and internal mass values, emphasizing the importance of accurate air infiltration modeling for overall model reliability.
... A pesar de emplearse un valor de permeabilidad a una presión conocida para la caracterización de la exigencia, este valor no expresa las condiciones reales a las que se va a encontrar la vivienda. Las viviendas suelen experimentar diferencias de presiones en torno a 0-10 Pa [3], [4], [5], [6] es por ello por lo que se necesitan modelos o correlaciones que permitan caracterizar la permeabilidad de la envolvente a lo largo de las 8760 h del año. ...
La permeabilidad al aire de la envolvente térmica juega un papel importante en la caracterización de la demanda de energía y principalmente en las temporadas de frío. Actualmente se emplean ensayos normalizados a presiones de referencia siendo el más común el Blower Door Test a 50 Pa. No obstante, dicha presión no refleja las condiciones reales de uso de la vivienda la cual estará normalmente entre 0-10 Pa y es por ello por lo que se emplean modelos que tratan de simular las infiltraciones en condiciones reales. Actualmente los modelos más empleados son el modelo del factor-N, el modelo de LBL y el modelo de AIM-2. El objetivo de este trabajo se centra en comparar los resultados obtenidos por estos tres modelos en una vivienda real en la cual se realizó un ensayo Blower Door Test, para ello se empleó como herramienta de simulación TRNSYS y se modeló el edificio mediante el type56. Los resultados arrojaron una media de un 17% de influencia en la demanda de calefacción.
The air infiltration rate of buildings strongly influences indoor environment and energy consumption. In this study, several traditional methods for determining the air infiltration rate were compared, and their accuracy in different scenarios was examined. Additionally, a method combining computational flow dynamics (CFD) with the Swami and Chandra (S-C) model was developed to predict the influence of the surrounding environment on the air infiltration rate. Two buildings in Dalian, China, were selected: one with a simple surrounding environment and the other with a complex surrounding environment; their air infiltration rates were measured. The test results were used to validate the accuracy of the air infiltration rate solution models in different urban environments. For the building with a simple environment, the difference between the simulation and experimental results was 0.86%–22.52%. For the building with a complex environment, this difference ranged from 17.42% to 159.28%. We found that most traditional models provide accurate results for buildings with simple surrounding and that the simulation results widely vary for buildings with complex surrounding. The results of the method of combining CFD with the S-C model were more accurate, and the relative error between the simulation and test results was 10.61%. The results indicate that the environment around the building should be fully considered when calculating the air infiltration rate. The results of this study can guide the application of methods of determining air infiltration rate.
Description
Provides you with both the underlying theory and examples of practical applications of models. 20 peer-reviewed papers discuss:
• interactions between sources and sinks of indoor air pollution
• problem areas related to model validation and their solutions
• application of models to evaluate ventilation performance and indoor air quality implications of proposed indoor space designs
• design and assessment of natural ventilation strategies and prediction of smoke movement
• use of models to predict formaldehyde and radon concentrations
• development and use of models to predict human exposures to toxic contaminants such as benzene.
In three sections: modeling and measuring sources and sinks; model validation and application; and modeling of exposures.
Description
The result of a changing technology, STP 904 presents the latest information on air infiltration. There are 23 papers in this book which is divided into four sections: residential; commercial and industrial; techniques for measurements and infiltration reduction; and analysis.
Description
The result of a changing technology, STP 904 presents the latest information on air infiltration. There are 23 papers in this book which is divided into four sections: residential; commercial and industrial; techniques for measurements and infiltration reduction; and analysis.
Description
The result of a changing technology, STP 904 presents the latest information on air infiltration. There are 23 papers in this book which is divided into four sections: residential; commercial and industrial; techniques for measurements and infiltration reduction; and analysis.
Infiltration studies have been carried out in a typical tract home in the San Francisco Bay area. Houses in this region as a result of the mild climate are loosely constructed, and show large air leakage rates. Infiltration rates of up to 1-1/4 air changes an hour were measured using a controlled flow tracer gas technique with nitrous oxide as the tracer gas. Air leakage rates were meausured using fan pressurization of the house with a range of pressures from 7.5 to 75 Pascals. In addition to weather data taken on site, pressure sensors mounted on the exterior walls were critical in establishing a pressure model for air infiltration. Measured inside--outside pressure differences were less than a tenth of those expected based upon wind speed measurements made on site. Measurements also show significant (20%) duct leakage and air flow between the attic, living space and crawl space.
A model is presented whose input is two sets of measurements: air leakage under fan pressurization; and natural pressure differences between indoors and outdoors. The output is the house's natural infiltration rate. The model was tested on six United States houses, three conventional houses located in a region of mild climate and three energy-efficient houses located in a cold winter region of the country. Good agreement was obtained between infiltration rates measured using a tracer gas and rates calculated from the model.
Many models have been devised to correlate air infiltration in buildings with weather parameters. A particularly promising strategy is to predict the air flow through the building envelope from surface pressures, which in turn are predicted from measured weather parameters. Due to interference of the weather, it is difficult to measure the pressure-flow relationship in a manner that is valid for the low surface pressures which have been observed to drive infiltration. Conventional techniques rely on steady-state (DC) fan pressurization or depressurization of the structure. DC-measurements are unreliable at pressures less than 5 to 10 Pa, but this is the pressure range that often drives natural infiltration. Thus, it is of interest to make direct measurements of air leakage vs. pressure in this low pressure region. Measurements of the leakage function measured at low pressures using an alternating (AC) pressure source with variable frequency and displacement are reported. Synchronous detection of the indoor pressure signal created by the source eliminates the noise due to fluctuations caused by the wind. Comparisons are presented between these results and extrapolations of direct fan leakage measurements.
The semi-empirical equations derived from an earlier laboratory investigation of flow through cracks are reconsidered and a revised method of application is proposed. The equations offer an improved technique for estimating the open areas of room components, and experimental results are presented to support this. The implications of the equations regarding scale effect are demonstrated both for full-scale and model-scale situations. Some results of ventilation rate measurements at model scale are presented which illustrate the effects both of scale and wind turbulence and also show the different flow characteristics of scale model windows and simple circular holes.
Heasurement of Infiltration in Two Residences
- D R Bahnfleth
- D T Hoseley
- W S Harris
D.R. Bahnfleth, D.T. Hoseley, and w.s. Harris, "Heasurement of Infiltration in Two Residences," ASHRAE TP.ANSACTIONS,. §1, 439-452, 1957.
Ventilation Research in Occupied Houses
- J B Dick
- D A Thonas
J.B. Dick, and D.A. Thonas, "Ventilation Research in Occupied Houses,"
J. Inst. Heat. Vent. Eng.,.12, 306-332, 1951.
Field Studies of Dependence of Air Infiltration on Outside Temperature and ·Hind
N. ~1alik, "Field Studies of Dependence of Air Infiltration on Outside
Temperature and ·Hind," Energy and Buildings, 1, 281-292, 1978.
Reconmendations for the Calculation of Wind Effects on Buildings and Structures
European Convention for Constructional Steelwork, "Reconmendations for
the Calculation of Wind Effects on Buildings and Structures" • Technical
General Secretariat, Brussels, Belgium September 1978.
Full Scale Heasurements on a Flat Roof Area
- K C Kim
- Mehta
s. Kim, K.C. Mehta, "Full Scale Heasurements on a Flat Roof Area,"
Proceedings of the Fifth Int. Conf. Wind Engineering, Boulder, Colorado,
July 1979.
Average Pressure Coefficients for Rectangular Buildings
- R E Akins
- J A Peterka
- J E Cermak
R.E. Akins, J.A. Peterka, and J.E. Cermak, "Average Pressure Coefficients for Rectangular Buildings, 11 Proceedings of the Fifth Int. Conf.
Wind Engineering, Boulder, Colorado, July 1979.