Liquid membranes transforming airtightness work — Blowerproof UK

This article was originally published in issue 37 of Passive House Plus magazine. Want immediate access to all back issues and exclusive extra content? Click here to subscribe for as little as €10, or click here to receive the next issue free of charge

Blowerproof was used as the primary airtightness layer on the UK’s most airtight building, the Imperial War Museum archive in Duxford.

“Since its introduction Blowerproof has been widely used by self-builders and contractors to seal difficult corners and junctions, but it has significant potential to serve as the primary airtightness layer on projects of scale,” said Will Kirkman of Blowerproof UK. “For example, Blowerproof has been used as the primary airtightness layer on over 270 passive-standard schools in Belgium to date, typically being applied externally.”

Kirkman said that this method, where the airtight membrane is applied to the external side of the inner leaf with insulation subsequently fixed directly to the membrane, has been comprehensively tested and proven as reliably secure with no loss of airtightness.

“The Belgian Schools of Tomorrow program recognised the benefits of eliminating internal detailing issues and the cost savings of using Blowerproof in this way, and the scheme established a common practice for achieving airtightness at scale across much of northern Europe,” said Kirkman.

Blowerproof is a VOC-free, water-based, flexible polymer that is brush, roller or spray applied to create a permanent airtight seal. Manufactured in Belgium by Hevadex, Blowerproof was brought to the UK in 2016 by leading sustainable building materials supplier Ecomerchant, the product’s UK distributor.

Blowerproof is BBA and Passive House Institute certified. To date Hevadex has manufactured enough of the product to cover 2,000,000 square metres. The company also estimates that it has been used on approximately 1,000 certified passive builds globally.

Perhaps the most high-profile project to use the product to date is the Imperial War Museum’s (IWM) rich paper collection in Duxford, which was designed to the passive house standard and achieved an airtightness score of 0.03 air changes per hour - the best airtightness test result in the UK to date, and joint best in the world, as far as Passive House Plus is aware.

The 1,238 square metre IWM building is approximately twenty times more airtight than the target for certified passive buildings and 200 times tighter than the current UK requirements for non-domestic buildings. The warrantied installation of Blowerproof at IWM was completed by Ultimate Coatings Limited (UCL), Blowerproof ’s appointed application contractor. The building was designed by Architype with Nick Grant as passive house consultant and Fabrite acting as the main contractor.

“The IWM store has been a great way for us to demonstrate the capacity of liquid applied membranes to secure high levels of airtightness on budget and on time. These results clearly demonstrate what a professionally applied and warrantied application of Blowerproof can achieve in terms of airtightness,” said Kirkman. See www.blowerproof.co.uk for more.