Last week BRE conducted the first airtest at Grove Road since work began on site. The test found the airtightness of the property to be 3.53 air changes an hour (ach-1). This a marked improvement on the original test in which the property was found to have an airtightness of 6 ach-1. However in order to achieve the desired Passivhaus Enerphit standard the project needs to reach an airtightness of 1ach-1. bere:architects have helped identify a number of areas for improvement with the Hounslow Homes team who are now taking the necessary actions to eliminate the remaining draughts.

It is interesting to note that if the airtightness had been calculated with standard industry methods the building would have reached an airtightness of 2.88 ach-1.

This is because the industry standard uses a volume calculation based on the entire floor area of the property. Airtightness tests on Passivhaus buildings previously used the industry standard ATTMA volume calculation but are now based upon a smaller volume, calculated from the treated floor area used in the PHPP software. Internal walls, chimneys, doors and window niches are therefore omitted from this calculation although stairwells are included. This recent change to the calculation method therefore makes it more difficult for Passivhaus buildings to achieve the same airtightness levels as previously.

Door blower fan applied to the front door as part of the airtightness test at Grove Road

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