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The Natural Philosopher

wrote:
Can anyone help? We are wanting to insulate between the rafters of our
attic roof which are about 90mm in depth. It is an old house (1900),
the roof is tiled and doesn't have roof felt or sacking so the
insulation would back on to the roof tiles. We have read you need a
space of 50mm between the insulation and the roof tiles and some
suggestions that instead of insulating between the rafters you should
insulate across them. My thoughts are to get some 50mm Kingspan
insulation and leave a 40mm to the tiles given the age of the house
and the fact that there is unlikely to be condensation problems given
the age of the house and there being no roof felt barrier. Is 50mm
enough? Are there any guidelines?
Any advice welcomed - thanks in advance.

I tyhink insulating across is a VERY good idea if you have the space.
You reduce the problems of cold bridging, and create a really decent
airtight vapour barrier as well. You would have to slea teh celotex to
the celing below top prevent draights under the celotex of course.

50mm sounds good to me. More is better.

Curious as to why you want a warm loft tho..normal practice would be to
insulate the ceiling below..