Air Tightness Testing
Something we get asked all the time with air testing is “How bad is that result?”.. Well, there’s no precise answer, as the result is dependent on many variables, but I will try to explain briefly here:
Firstly, the higher the result, the more air is allowed to escape through the building fabric. A leakier building will lose more heat energy as warm air is allowed to pass through gaps in the building, with colder outside air being drawn in to replace it.
So, what result is desired and or required for a “pass”?
Well - this depends on what the SAP calcs demand, or maybe there’s a special requirement (e.g. Passivhaus requires 0.6 ACH - air changes per hour, which is roughly equivalent to 1.0 m³/m²/hour at 50Pa). The maximum result allowed to be entered into SAP calculations is 10.0 m³/m²/hour at 50Pa but generally the actual target required to pass in SAP is usually much lower, at around 5.0.
But what does a result of 10.0 mean?
A result of 10.0 is the equivalent of a hole the size of a 20p coin in EVERY m² of the surface area of the building - that’s a lot of holes, which for an average house would be about the same as having one 30cm diameter beach ball-sized hole in the building fabric... WOW