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Coating The Most Airtight Building in Europe

Blowerproof airtight coating helps secure the most airtight building in the UK


The Imperial War Museum is home to an extensive collection of historic original documents, from photographs to wartime letters and ledgers. 

A state-of-the-art archive building was built to preserve this rich paper collection and protect it from any degradation. This required an airtightness system that ensured a carefully controlled environment that maintains optimum levels of temperature and humidity.


An effective and reliable airtightness coating was essential to achieving the required control of the room conditions. On top of this, the client needed a product that would stand the test of time, as the contents of the room needed protection for generations to come. With these criteria in mind, we proposed BlowerProof (BBA Certified) as the most effective solution for this project. 

However, when it came time to apply the coating it became apparent that further consideration was needed to effectively execute the work.

The whole construction team observed that once a line is drawn on a plan, delivering said line is a whole other matter. The reality of making a building passive with an airtight membrane is more complicated than just putting the coating on the wall”, said Marcus Locket, Managing Director of Ultimate Coatings. 

With the help of all teams involved, a new approach was designed. “Thanks to the fully cooperative attitude and input from Fabrite, UCL, and the design team at Architype, we delivered the most airtight building in Europe to date,” said Marcus.

With the new plan in place, we inspected the internal brickwork for any large cracks. Any that were over 5mm were infilled with our flexible mastic. Following this, two coats of BlowerProof were spray applied to 1,238m2 of internal concrete brickwork. After the first coats, the UCL team had concerns regarding the porous nature of the concrete block, so we conducted a preliminary air test. As a result, an additional coat of BlowerProof was applied to the entire area.


The building achieved a final airtightness score of 0.03 changes per hour (ACH) at 50 Pascals – breaking the record for airtightness in the UK. This score is 20 times tighter than the target for certified passive buildings and ~200 times tighter than the UK requirements for non-domestic buildings. 

A collaborative approach is the only way to achieve the new standards for airtightness. It has to be a way of life, a state of mind, rather than ‘just another trade to value engineer’”, said Marcus Lockett, Ultimate Coatings Managing Director. “To deliver exceptional results, the main contractor must have a truly harmonious partnership between the airtightness team and the design team”.

Fabrite’s Nigel Johnston agreed, stating “working together allowed Fabrite to shine, deliver the project on time, on budget and exceeding the requisite airtightness standard

Category: Airtightness

Client: Imperial War Museum

Location: Duxford, England

Surface Area: 1,238m2

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