SIPs create a virtually airtight envelope. This is fantastic for energy efficiency, but it requires a rethink of how we ventilate our homes.
The Importance of Airtightness
Drafts are responsible for a significant amount of heat loss in traditional UK homes. By sealing the building envelope, we keep the heat in.
Mechanical Ventilation with Heat Recovery (MVHR)
When a building is very airtight (often less than 3 m3/h/m2 @ 50Pa air permeability), natural ventilation through trickle vents is often insufficient.
How MVHR works (simple version)
- Extract stale, moist air from "wet" rooms (kitchens, bathrooms).
- Recover heat in the MVHR heat exchanger (the air streams pass heat across a core and do not mix).
- Pre-heat incoming fresh air using the recovered heat.
- Supply warm, filtered air to "dry" rooms (living rooms, bedrooms).
Key terminals
- Fresh air intake: outside -> filter -> MVHR unit.
- Stale air exhaust: MVHR unit -> outside.