Coating The Most Airtight Building in Europe

Introduction

UCL Ltd was appointed to apply an airtight coating system to a new archive building at the Imperial War Museum, Duxford. The facility was purpose-built to preserve historic documents — including wartime photographs, letters, and ledgers — requiring a precisely controlled environment with strict temperature and humidity parameters across 1,238m².

Our Solution

Following inspection of the internal brickwork, all cracks exceeding 5mm were pre-filled using a flexible mastic prior to coating application. BBA-certified BlowerProof liquid airtight coating was then spray-applied in two coats across 1,238m² of internal concrete blockwork. A preliminary air test was conducted after the initial coats, identifying areas where the porous nature of the blockwork required additional treatment. A third coat of BlowerProof was subsequently applied to the entire surface. The approach was developed collaboratively with main contractor Fabrite and design team Architype, recognising that achieving true passivhaus-standard airtightness demands close coordination across all trades and disciplines throughout the construction programme.

Key Benefits

• Achieved a final airtightness score of 0.03 ACH at 50 Pascals — the most airtight building recorded in Europe at the time
• Performance is 20× tighter than the certified passivhaus standard
• Performance is approximately 200× tighter than UK regulatory requirements for non-domestic buildings
• BBA-certified BlowerProof system provides long-term durability suited to a heritage archive environment
• Preliminary air testing mid-application allowed real-time quality control and informed additional treatment
• Project delivered on time and within budget

Conclusion

UCL Ltd delivered a record-breaking airtightness result for a critical heritage archive, demonstrating that exacting environmental standards are achievable through rigorous surface preparation, appropriate product selection, and structured collaboration between specialist trades and design teams.