Outlines causes of air infiltration. Discusses the air leakage paths of openings and measures that can be taken to reduce air leakage. Concludes that air infiltration should never be relied upon for ventilation but efforts should be made to make the building envelope more airtight, and a mechanical ventilation system should be installed.
Reports low-pressure measurements of the leakage function of a building using an alternating (AC) pressure source with variable frequency and displacement. Synchronous detection of the indoor pressure signal created by the source eliminates the noise dueto fluctuations caused by the wind. Finds good agreement between AC and DC leakage results in pressure regions where the results can be compared. The low-pressure values made with the AC source suggest that the air flow is dominated by orifice flow effects down to pressures less than one Pascal.
Presents a model for predicting air infiltration that eliminates many site- specific parameters normally required. The only information necessary is the geometry and leakage of the structure obtained from fan pressurization measurements. Theleakage 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.
Describes computer program for the prediction of the air infiltration load in small residential buildings. The model represents an oil-fired furnace, a smoke pipe with barometric damper, a chimney and a non-partitioned building, with leakage openings in the building envelope. The model can be used to predict the air change rate of a small house under various combinations of indoor/outdoor temperature, wind-speed, wind direction and operation of an oil fired furnace.
Outlines the problems of modelling air infiltration. Reports measurements of the leakage function measured at low pressures using an alternating pressure source with variable frequency and displacement. Synchronous detection of the indoor pressure signal created by the source eliminates the noise due to fluctuations caused by the wind. Presents comparisons between these results and extrapolations of direct fan leakage measurements.
Briefly discusses wind-pressure on buildings. Derives equations for air-flow in a building without internal walls caused by wind pressure from perpendicular and oblique wind. Gives simplified method for calculating air flows inside a building with internal walls. Gives tables showing results of calculation of air flows for a building with two and three rooms. Discusses more complicated building types and gives results of calculation. Outlines determination of ventilation heat loss, air leakage of windows and doors.
Describes methods of measuring the air tightness of whole buildings. Outlines three tracer gas methods; constant concentration; decreasing concentration and constant emission. Describes pressurisation method. Describes measuring equipment and test procedure and discusses calculation of ventilation rateand error magnitudes. Gives brief summary of measured results and an appendix contains a print-out of data on the airtightness of houses.
Reports model scale experiments to investigate the validity of digital analogue methods of predicting natural ventilation. Finds calculated ventilation rates up to 30% higher than observed model ventilation rates. Shows differences between observed and computed results caused by operating efficiency of ventilation openings being less than calibrated efficiencies. Corrected ventilation rates, allowing for changes in efficiency due to pressure fluctuations and lateral air flows over model surfaces showed close agreement with observed results.
Examines ways in which air leakage affects building performance. Heating load and building relative humidity in winter are affected by over-all air infiltration and ventilation rates. Windows and doors usually represent the major source of air leakage in buildings. Condensation problems occur when exfiltrating air deposits moisture on surfaces such as atticsand inside double windows. Discusses ways of reducing condensation. Finds that air tightness in inside of enclosure must always be many times greater than that of the outer cladding.
Reports measurements of air change rates made on approximately 250 dwellings, occupied by low income households in 14 cities, in all major climatic zones of the United States. Two types of measurements were used : a tracer-gas decay technique using air sample bags and a fan depressurization test that measures induced air exchange rates. Shows that for this group of dwellings natural air infiltration rates have an approximate lognormal distribution.
Login