Just saying because I am pleased about it.
New house passed its air permeability test today. The tester basically puts a 2 foot diameter fan in an external doorway, with the surround sealed to the frame, and sucks air out of the house causing a 50Pa pressure drop (0.0005 bar) The rate at which the pressure rises again or the amount of suck required to maintain it is measured and they come up with a leakage value in "m³/(h.m²) @ 50 Pa". Our design value is 3.0, which we hit. Building regs specify a maximum of 10.
I think most developers work to 5.0, but as we have a mechanical ventilation system we have no window vents etc. so 3.0 becomes a reasonable target which contributes to a good energy rating. The air test is needed to get the energy performance certificate.
As you were.
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