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How do you insulate sloping ceilings?

Our house has sloping ceilings to all the upstairs rooms. The horizontal ceiling accounts for around 40% of the total ceiling area and is insulated with glass fibre between the joists, accessed via the loft hatch.

However, this leaves a lot of uninsulated sloping ceilings with little room (around 5 inches) between the plasterboard and the roof tiles. The only access to these voids is by peering down at 45 degrees, once you are in the main loft space.

I must be losing a lot of heat via the sloping ceilings. How can I insulate these sloping spaces between the rafters whilst allowing for sufficient ventilation? I should mention that I'm not keen on insulating from inside the bedrooms. The ideal scenario is to find a way that allows me to insulate from above but still keeping ventilation to the roof space and avoiding condensation...

...and I don't want to do the work myself!


2 Answers from MyBuilder Insulation Installers

Best Answer


If you don't want to strip the ceiling to use celotex/kingspan insulation cut between the rafters (this should still leave a void for ventilation) You'll have to strip the roof...


Answered 20th Dec 2011

The only way to insulate it, without removing the ceilings is, if possible fit some rigid insulation board to slide down between the timbers.
You only have 5 inches and you need minimum 50mm air flow between board and tiles so you might get away with 75mm kingspan.
You will need to check you have ventilation between the two.


Answered 19th Dec 2011

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