A loft conversion is usually the room with the worst indoor-air-quality in the house, and a small MVHR unit serving the loft alone is a more sensible answer than a whole-house retrofit.
Before any kit conversation, the building tells you what is possible. A loft conversion typically presents single skin of insulation between rafters. Most also carry velux roof lights. These facts shape every later decision about comfort.
The most common issue this property surfaces is bedroom overheating, followed by stuffy air. Any sensible plan addresses those first.
The constraint is space. The unit, the ducts and the summer bypass all need a home, and most loft conversions have already given that home to a bed or a bathroom. The trade-off is usually a shallower wardrobe or a cupboard the family had not planned to give up.
A compact single-room or two-room heat-recovery unit ducted from the eaves on either side of the conversion handles the moisture and stale-air load without the disruption of running ducts down through the house.
Pair the unit with an honest summer bypass and a roof-light blind and the conversion goes from the room nobody wants to sleep in by August to the calmest part of the house. Both decisions cost less than the original cooling kit most owners reach for first.
The published cost range for this work lives in the cost registry, not on this page. The scope it covers is mvhr system, full house install with ductwork.
A single-floor heat-recovery unit costs materially less than the published whole-house figure; treat that number as the upper bound, not the typical loft case.
Loft conversions are the room where the case for heat-recovery ventilation is easiest to make and the easiest to scope sensibly. The owners who treat the loft as one floor's problem rather than the trigger for a whole-house retrofit get the comfort gain without the cost of a project that the rest of the house did not need.
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