Air tightness definitely heading in the right direction!

Now that the attic roof and the extension roof have been "taped and membraned" to the hilt, we've had an air tightness test to see whether we are anywhere near the EnerPHit target of 1 ACH @ 50 Pa.

The average of the de-pressurisation and pressurisation (sucking air out and blowing air in) values came out at 1.078 ACH @ 50 Pa, which is certainly cause for optimism! We are extremely grateful to our merry band of Eco House Group helpers who came along and tracked down draughts during de-pressurisation, or went round with tape and sealant blocking up the draughts identified. While some draughts are easy to spot and solve, it is truly amazing how some draughts can be felt, but no obvious hole or fault in the taping can be seen.

In the days following the test there were some worrying moments when the plasterboard went on as this can stretch or puncture the membrane if it is a little tight in places (almost inevitable in a complex roof structure like this one). However, improvements elsewhere cancelled out any small issues which we could not detect behind the plasterboard, so we are still on track.

As long as the remaining refurbishment work results in a few improvements and no mistakes, we should be able to get below the magic figure of 1. But success is by no means guaranteed so we'll be waiting until the very end to find out if we have made it.

For those more familiar with the other way of expressing air tightness (air permeability), Midland Energy Services has also provided that figure: 1.07 m³/h.m² @ 50 Pa.

Air Permeability and Air Changes per Hour do not necessarily match, but in a medium sized house like this one, they can do. For a small flat or a large hotel, the two figures would be very different.