air leakage

Describes LBL's Mobile Infiltration Test Unit (MITU) which spent the 1980-1981 winter in the field collecting the data required for infiltration modelling. Data included measured infiltration rates, surface pressures, wind velocities, indoor and outdoor temperatures, leakage area and leakage distribution. Comparisons of measured infiltration rates with values calculated from surface pressures (using MITU) have shown no decrease in accuracy when a square-root flow model is used instead of the general power-fit model of leakage.

The needs, history, procedures, and past case studies for the house doctor approach are outlined. This program of individualized instrumented energy audits and retrofits has reached a stage in development where steadily increasing numbers of house doctors are envisioned for the years immediately ahead.

Outlines a method for measuring the air leakage through the surface exteriors of an apartment, by adjusting the pressure of the adjoining apartments to that of the test apartment, so that no air leakage occurs through adjoining walls.

The air tightness of buildings is part of an investigation performed by the State Research Centre of Finland. Regulations are being developed in Finland for the maximum allowable leakage in buildings. These can be stated as 0.2 ach/hr for residences, 0.1 ach/hr for low apartment buildings, and 0.2 ach/hr for high rise buildings. Tightness can be measured using a suitable fan connected to a board in a window or door opening, or by thermography.

Gives air leakage measurements which show that improvement of the tightness of the outer core of a building gives an energy saving of 5000 Kw/a in comparison to a conventionally constructed building.< Finds that the most leakage occurs at the joints of walls and ceiling, followed by the breakthrough for electrical wiring, the corners of the buildings, the windows, the joints of wall and floor and the joints of ducts and ceiling.< Older houses in Sweden have approximately the same rate of leakage as in Finland, ie 5-10 changes per hour at 50 pa.

Shows that the leakage test in most buildings with mechanical ventilation may be performed with the ventilation system itself with only a slight reduction in the accuracy of the measurements. Using fans in the ventilation system, the pressure difference inside/outside may often reach a measurable value of 5-10 pa. If such a pressure difference is not obtained, the leakage exceeds allowable values and the building should be tightened. Before measuring, all of the supply air openings in outer core of the building should be closed and taped. All doors inside the apartment should be open.

Reports measurements on air transport through homes made by a committee working a Dutch Standard on Heating Load Calculation similar to DIN 4701, but taking account of air infiltration losses through joints and cracks between glazing, window-frame and facade construction. Describes the measuring method applied. Tables air leakage coefficients c and flow exponents, n ,of a number of flats and single family houses. Also tables c and n values of cracks according to type of construction and material, use of weather strips and measuring institute.

Discusses and analyses the characteristics of methods of determining local air flows through the building envelope, methods of determining the air leakage and ways of determining air changes in rooms. Summarises in a table methods of determining local air flows. Of the air leakage methods, treats static and non-static methods. Considers three commonly used tracer gas methods for air change measuring methods.

Describes an energy audit being developed at LBL to determine economically optimal retrofits for residential buildings, based on actual, on-site measurements of key indices of the house. Measurements are analyzed on a microprocessor and retrofit combinations compatible with minimum life-cycle cost and occupant preferences are then determined. An important element of this audit is its treatment of infiltration.

Describes tests performed on laboratory manufactured and prefabricated concrete specimens, to determine air leakage rates through cracks. Shows the expected increase of air leakage for increasing crack width and the decrease for increased element thickness. Appropriate theoretical assumptions are described, and the results show relationships for the calculation of the magnitude of air leakage through cracks.