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Mist-applied sealant could improve air tightness in buildings

Andrew Pearson

AeroBarrier, a mist-applied sealant system, can improve airtightness by sealing gaps in a building’s envelope of up to 12mm diameter

Mist-applied sealant system AeroBarrier.
Mist-applied sealant system AeroBarrier. Credit: AeroBarrier

A mist-applied sealant system that improves a building's airtightness has been launched in the UK as AeroBarrier. The system, which is established in the US and Canada, can seal gaps in a building's envelope of up to 12mm in diameter.

The sealing process takes place once construction has reached second fix. Before the sealant can be applied, the space is prepared by sealing all intentional ventilation openings, such as vents and fire places, in addition to protecting horizontal finishes. The building is then pressurised using a fan in the same way it would be for a Building Regulations air-leakage test.

With the building under pressure, a water-based, non-toxic acrylic sealant is sprayed as a fine aerosol mist from dispensing stations located in the various spaces. Entrained in the pressurised air, the sealant mist is drawn to gaps in the envelope by the air as it leaks out of the space. As it passes through the openings, the sealant is deposited around the edges of the gaps, where it accumulates and solidifies to form a vapour-permeable caulk-like seal.

New build house sealed up ready for application of the sealant.
New build house sealed up ready for application of the sealant. Credit: AeroBarrier

Real-time monitoring enables sealing stations to be turned off once the targeted air leakage rate has been achieved in each space. Excess sealant can be wiped from surfaces while it is still damp using a citrus-based cleaner. 

‘In general we see an envelope leakage reduction of anywhere between 40 and 95 per cent,’ says AeroBarrierUK head Hugh Franklin, adding: ‘If a building achieves Building Regulations airtightness, we can take it to the next level.’

The application process is warrantied by AeroBarrier for 10 years, while the sealant has been shown to be effective for over 50 years under third-party simulated environmental stress tests.

Franklin says this particular system is oriented towards new build, although retrofitted buildings are ‘definitely’ on the horizon. ‘There is no reason why we cannot do retrofit,’ he says, ‘but it is a lot of prep work, especially if you have finished surfaces in a building, because we need the sealant to be able to access every point of potential air leakage in the building envelope.’

  • Inside a room with the sealant mister.
    Inside a room with the sealant mister. Credit: AeroBarrier
  • Test seal of AeroBarrier.
    Test seal of AeroBarrier. Credit: AeroBarrier

According to Franklin, the system does not come under the construction products regulations ‘because of the nature of the product and its application’. However, it has been tested for compliance with ASTM and UL standards, which are both US-based standards organisations. ‘We have plans to reference European Standards,’ he says. ‘We are working with the NHBC to get the standards buttoned up and a full Agrément Certificate.’

AeroBarrier is also putting together an Environmental Product Declaration including a life-cycle carbon analysis. ‘We're doing parts A1-A3 of the EPD at the moment, which covers manufacture of the product,’ Franklin explains.

Life-cycle carbon of the product will be important if the proposed Part Z amendment to the Building Regulations is adopted. Part Z is intended to ensure that embodied carbon is assessed on all projects as part of a comprehensive whole-life carbon assessment.

Read more about AeroBarrier

Read how LEAP Architects created the UK’s most airtight home



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