ventilation of roof space?

[Jim Chisholm]

I've had soffit ventilators for 25 years, and recently tripled insulation in the loft and fitted refurb rafter ventilators to ensure air had free passage from soffits. I've roof felt rather than permiable membrane but although I've had no sign of obvious condensation, I'd thought of fitting vent tiles near to ridge. BUT someone said 'no need' just wedge a bit of polystyrene between overlapping layers of roofing felt, and that gives adequate ventilation.

Questions: Does that work? What stops wasps entering loft to make a nest?

Jim Chisholm

[Andrew Gabriel]

I used 25mm or 30mm oval electrical conduit. Cut lengths a couple of inches longer than the felt overlap. An inch from one end, cut almost through but not quite, and bend back to make a hook so the piece can't slide right through. Use a pair of these between the rafters, spaced so the felt is held apart between them. If you use them all the way along, that's pretty much the continuous 10mm gap required by modern building standards (and much less that this was used for many years).

I used these on the bottom felt overlap because the house has no soffits and very little opportunity for ventilation at the eaves.

Advice here was that high up vents can help draw in cold misty air in the winter, so I didn't put any high up.

I get wasps in the loft occasionally, but so far, not via that route. It will probably happen eventually, but that's not a reason not to do it.