Mendip Energy - SAP assessment and domestic air pressure testing

Mendip Energy, energy performance consultants

what is air leakage?...
Air leakage is the uncontrolled flow of air through gaps and cracks in the fabric of a building. This is not to be confused with ventilation, which is the controlled flow of air into and out of a building through purpose built ventilators that is required for the comfort and safety of occupants. Too much air leakage leads to unnecessary heat loss and discomfort to the occupant from cold draughts.

The increasing need for higher energy efficient buildings and the need in future to demonstrate compliance with more stringent building regulations targets means that air tightness has become a major performance issue.

The aim should be to build tight - ventilate right.

what are the requirements?...
The test is needed near the completion of the build to establish how much uncontrolled air leakage occurs. The score is a measure of the amount of leakage divided by the area of the dwelling.

PassivHaus air testing...
PassivHaus developments are becoming more commonplace and as these types of properties or dwellings have much lower air permeability rates the air testing procedure has to adapt to suit the lower levels of leakage. Mendip Energy is fully qualified to carry out pressure testing to n50 and q50 as both results will be needed, the first for PHI compliance and the second for SAP compliance which is still required by building control.

why should we test?...
Gaps and cracks in the building fabric are often difficult find visually. Air leakage paths through the building fabric are obscured by internal finishes and external cladding. The only satisfactory way to show the building fabric is reasonably air tight is to measure the amount of leakage over a measured time period. Air leakage is quantified as Air Permeability. This is the leakage of air (m3/hour) in or out of a building, per square metre of building envelope at a reference pressure of 50 Pascals between the inside and outside of the building. This is shown as... m3/(h.m2)@50Pa The general requirement under current building regulations for domestic and non domestic buildings is for the building to be tested to comply with a maximum air permeability of 10m3/(h.m2)@50Pa

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