Re: Re: Energy Efficiency/New Building Regulations

Air tightness refers to the uncontrolled infiltration of air into or out of a building when it is positivly or negativly pressurised. Air infiltration can be by channel flow through cracks or diffuse flow through permiable materials such as blockwork. Air leakage can be defined as:
“The uncontrolled movement of air in to and out of a building which is not for the specific and planned purpose of exhausting stale air or bringing in fresh air.”
Air leakage is measured as…
The rate of leakage per square metre of external envelope per hour at an artificial pressure differential through the envelope of 50Pa(m3/hr/m2 @ 50Pa). All wall, roof and floor areas that are exposed to the external environment are included within the calculated area. Floor slabs in direct contact with the ground are not included, on the basis that they will not allow any significant levels of leakage to occur.

Naturally ventilated Houses generally perform at about 9m3(h.m2) @50 pascals with of course ventilation openings sealed for the purpose of the test, best practice is 3m3hm2@50 pascals.

A leakage rate of 10(m3/hr/m2) @50 pa for a 2000m2 building would be the upper threshold of the UK part L regs, I will equate this to an air changes per hour rate, I think it is about 1.2, where 0.3 is desirable, 0.1 has been achieved in some low energy houses in north dublin.

more details to follow, I have a problem that the draft part L regs dont seem to set any benchmarks, need to read up on it more thoroughly, PM me if you need air testing info, i have a presentation i can email.