Summary
Most existing homes rely on natural ventilation (essentially, opening windows) or intermittent extract fans (e.g. in kitchens and bathrooms) which can be ineffective at ensuring good air movement in all rooms in a home.
Inadequate ventilation can lead to surface or hidden condensation, damp and harmful mould growth. These issues can create poor environmental conditions for occupants and can exacerbate a range of health conditions such as asthma. They can also cause damage to the building fabric/structure (e.g. rot).
A well designed and functioning ventilation system/strategy is key to avoiding these issues. There are a number of ventilation systems available, ranging in cost, complexity and effectiveness. Continuous ventilation is preferred, extracting unwanted, stale, moist air from ‘wet rooms’ (bathrooms, kitchen, utility rooms etc.) and delivering appropriate amounts of fresh air to ‘habitable’ rooms (living rooms, bedrooms, and studies etc.).
One available system is MEV – Centralised Mechanical Extract Ventilation. This is very similar to dMEV. In place of a unit in each room, ducts take stale air to a central extract fan unit from each ‘wet room’. The larger single fan can improve reliability, reduce noise and provide better volume control. They are also often easier to clean and otherwise maintain. Each ‘habitable’ room needs planned intake air points, whether via trickle vents in windows or wall mounted vents.
Cost/difficulty
MEDIUM COST
MEDIUM DIFFICULTY
Applicability in Letchworth
Applicable – No specific requirements.
Insights from ASBP
“Comment on breathability and ventilation TBC.”
Case study
Case study TBC
Read more
Links to further information
- HCCSP Retrofitting Your House Guide (2024), page 23
- Saltaire Retrofit Handbook (2024), page 44
- Retrofitting Your Home – Cambridge Guide (2022), page 21
- The Surrey Home Energy Improvement Guide (2025), page 49
This guidance is part of Ventilation
See more guidance notes on this topic below: