Low Cost Blower Door
Heat loss through “air changes” - air flowing out of a house through draughts, vents and holes - is huge. An old and unimproved house might have 4 air changes every hour. For a typical 3 bed house on a cold 0 degree C day, that means 6 - 8kW being lost through leakage alone.
The actual energy cost is incredibly variable, so I wrote an interactive tool to calculate it.
At the new gas price cap of 7.37p/kWh, that means as much as £14.15 a day spent heating air which blows out the house.
The industry standard method of testing for air leakage is the blower door. This is a large fan which is sealed across and opening (usually a door) and which blows air into the house until the house is 50 Pa above ambient pressure. The airflow is then measured, and an air leakage rate (in m3/hr/m2 of floor area) can be calculated.
All new build houses must have this test done, but most older houses never do.
Current blower doors are made by a few manufacturers. They’re expensive (£2000+), bulky, and make use of lots of complicated equipment (eg a laptop running specialised software). Typically someone might hire them out for a few hours to perform a test.
During a test, draughts and holes reveal themselves. A smoke pen or incense stick can be used to find these. Even small holes will result in a fairly big draught at 50 Pa.
There would be a big benefit to low cost, accessible blower doors.
- They could be set up permanently and used regularly while hunting down leaks to improve a house
- Sealing draughts would become an instantly measurable activity - the feedback loop would be minutes rather than months
The components of a blower door are quite simple.
- A fan which is capable of blowing enough air at a 50 Pa static pressure
- A differential pressure sensor which can measure 50 Pa
- A control system which can control the fan speed to maintain 50 Pa
- Mechanical design to seal the system to a door or window opening