Existing House, Milton Keynes

Existing House, Milton Keynes

Client: Homeowner
Testing: Air tightness & Identification of Leakage paths
Lead Test Engineer: Tom Gregory



The homeowner had recently purchased this 1980’s 3 bedroom detached house and found that it was difficult and expensive to heat. This also meant that it was uncomfortable especially when working from home all day.

Air Tightness Testing:

An initial air tightness test was conducted on the house which produced a result of 13.4 m3.h-1.m-2@50Pa. This is someway over the current maximum allowed in the Building Regulations for New Builds which is ’10’ (soon to be reduced to ‘8’). Most new build houses need to achieve ‘5’ or less so a ’10’ is already pretty draughty (the equivalent of a 20p piece-sized hole in every square metre of the external building fabric).

Negative pressure was created to show up the draughts as air flow inside the property which demonstrated the worst areas, the bathroom, utility room and kitchen. These areas were isolated and the test repeated to gauge the level of impact from each area in order that the most significant leakage paths could be prioritised. If the leakage from these areas was addressed the air leakage would halve which, would have a significant impact on heating costs and comfort levels.

Leakage paths:

Under depressurisation, we were able to pinpoint the leakage paths in each room. These were demonstrated to the homeowner, they were photographed and noted (it would be possible to video these as well using smoke). Some of the most significant areas were addressed there and then using expanding foam and flexible sealant.

A report was produced detailing the results and the leakage paths, highlighting the most significant ones and recommending solutions so remedial work could be completed in priority order and/or as other improvement works are undertaken.

The option of infra-red imagery to identify possible breaks in the continuity of insulation was not taken up in this case as the homeowner had already been advised that additional insulation could not be practicably installed.


“With the temperatures dropping, I knew there was an issue with my house. Rather than upgrading the heating, I wanted to know why the house was so draughty. The services offered by ALT were brilliant, they quickly identified the main issues in the house and the areas where I was losing the most heat. Now I have a clear plan around which areas to address and in what order, so I can make the house warmer and more energy efficient.”

Ms M Perry