Attic insulation, 30 cm rafter spacing

[Francis Kirby]

Attic insulation, 30 cm rafter spacing. What would be best way to insulate with this narrow spacing. Could I use spce blanket streatched over rafters?

[Rod]

I simply read that in the wrong way. It was me, not your post, but I wanted to respond:

But the parthenon didn't have insulation. :-)

[Andrew Gabriel]

I would get a roll of 100mm insulation (used for topping up), and cut it into several 30cm wide rolls. (This is quite easy with a long kitchen knife -- do it with the roll wrapping still on.) Some rolls come sort of pre-perforated for cutting to certain joist separations. If there's a 30cm pre-perforated one, go for that. Otherwise try to get one which isn't pre- perforated.

Having laid this between the joists, then lay another 100mm layer (or more if you want) uncut full width across the top at right angles.

The space blanket stuff has been discredited.

[<me9]

Has it? there's nothing wrong with this -- and it doesn't get up your nose and in your throat. Pity it only comes in 370mm, I need 600mm.

[Martin Bonner]

That stuff's fine. It's the stuff that /just/ consists of sheets of metalized polythene that is a waste of time/money.

[a]

Thanks for the info. I've changed my news server, hence the delay in responding.

I was going to do the roof rafters rather than the floor joists so to speak. How do I keep the insulation in place?

[Martin Bonner]

That probably makes the solid board (Kingspan, Celotex) a more attractive option. Cut to a friction fit, and just push between the rafters.

[stuart noble]

Or use Rockwool slabs. Cheaper than foam, and just as easy to maintain the 50mm gap under the roof tiles