Loft hatch U-values by maker
A U-value measures how much heat passes through the hatch. The lower the number, the less heat gets through it.
| Maker | U-value range | Test method stated? |
|---|---|---|
| FakroRange covers several hatch models | 0.51–1.1 W/m²K | Not stated on the pages read |
| TB DaviesRange covers several hatch models, not one fixed figure | 0.59–1.3 W/m²K | Not stated on the pages read |
These ranges come from Fakro's and TB Davies's own published pages, read on the date given with the figures. Neither maker's page states which test method produced the figure, so a lower number cannot be read as directly comparable between the two without knowing that.
Does the airtightness rule for loft hatches apply to my house?
Approved Document L sets a requirement for loft hatches, but it only applies in one circumstance. Paragraph 4.21(i) concerns new dwellings where the roof is insulated at ceiling level, and it asks that the hatch into that loft be designed and fitted for good airtightness.
If you're replacing a hatch or ladder in a house that's already standing, this paragraph doesn't reach you. It's written for new build, at the point the roof and ceiling are being insulated for the first time. An existing home with a draughty hatch isn't being assessed against this provision, whatever the state of the seal around it.
That distinction matters because the two situations call for different things. A new dwelling has the requirement built into its design from the start. An existing home has whatever hatch is already there, and the question for most readers isn't which regulation applies but what to check and fix.
Checking a draughty loft hatch
A draught round a loft hatch usually comes from one of three places. Working through them in order tells you which one it is.
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Seal round the frame
A compressible strip fitted where the hatch door meets its frame closes the gap that opens up as timber moves with the seasons.
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Insulation trimmed flush at the edge
Loft insulation piled up over the hatch frame without being trimmed back leaves a gap at the edge for air to move through, even with a seal fitted.
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Latch pulling the door tight
A latch that has worked loose lets the door sit slightly open under its own weight, which undoes the seal whatever state it is in.
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Hinge alignment
A door that has dropped on its hinges no longer meets the frame evenly, so the seal only closes part of the gap.
Where the hatch still draughts with all three in order, the fault is more likely in the hatch itself than in the fitting.