Projects that include measures likely to affect a building’s airtightness, such as insulation or new windows are now required under PAS 2035:2023 to have a clear airtightness strategy in place. This strategy can include the setting of airtightness targets and the use of air leakage testing to confirm performance. By reducing unintended air leakage, these measures can significantly improve energy efficiency, but they also make it essential to provide suitable background and mechanical ventilation aligned with Approved Document F. Without a coordinated plan, there’s a risk of increased damp, mould, condensation and poor indoor air quality – Seal it Tight, Vent it Right. 

Airtightness sits within the broader whole-house approach, which considers how all elements of the building work together. If the building fabric is being upgraded, ventilation must be addressed at the same time to ensure the internal environment remains healthy and comfortable. This is especially relevant in light of Awaab’s Law, which is coming into force from October 2025. The law places legal duties on social landlords to fix serious issues like damp and mould within strict timeframes, highlighting the real world consequences of getting ventilation and moisture control wrong. The aim is not just a more efficient building, but a safer and healthier one too.