Resistance to air flow through external walls.

Summarises data on air flow characteristics of walls from U.S.A. and Norway. Reports laboratory measurements on four test walls and identifies main sources of leakage for the different test facades. Average air leakage at 200 Pa varied from 5m3/h/m2 to 50m3/h/m2. Shows that wall leakage rate could provide 30% or more of the total leakage rate.