Loft insulation

[MATB1]

The old owners of our house left loads of loft insulation stuff in the loft. DH is going to put it on the floor of the loft over the weekend. He's also been talking about putting celotex on the inside of the roof too. It's a big job and we're short on time so I'm wondering whether a) we actually need to do the celotex if the floor as been done, and b) should we pay someone to do it rather than have DH spend precious weekends doing it.

Any tips or advice? Thanks!

[roneik]

Make sure you lag any pipes and insulate any tanks, they will not have the benefit of the heat that got through before you insulated.

[PigletJohn]

Celotex is expensive. However it has about twice the insulating power of the same thickness of mineral quilt.

Current standard for loft insulation is 270mm of mineral wool. That means it is so thick that the loft timbers will be buried so it is difficult to walk about up there. If you are going to board it, you can fix foam insulating slabs to the tops of the timbers, and board on top of that.

Because of the pitch, if you want to insulate the rafters, there is more than twice the surface area to cover.

[roneik]

Insulating just the floor of the loft isn't a big job , should take less than 3 hours. Wear a mask and some goggles if using rockwool
If a fit pensioner can do in that time so can you.
Unless you are planning on living up there don't worry about the thickness.

[MATB1]

Thanks both.

Agreed that the floor isn't that big a deal (though with 4 double bedrooms and a bathroom on the first floor it is a lot to do). We've also got a lot of stuff up there so moving it all about is a palaver.

DH is a carpenter so I think he'll have the boarding under control and can get hold of celotex ok. So it's more about how much it's really worth doing the rafters as well as the floor? And if it really is worth it that's probably a couple of weekends' work, no? What with stop starting around the demands of two children under 3!

[PigletJohn]

You do the rafters if you want to make the loft into a warm living space, e.g. if DH is going to play with his Scalextric or homebrew kit up there. Otherwise it is normal and correct for a loft to be cold and draughty, which keeps it ventilated and dry.

It sounds like he knows how to do the insulating slabs plus boarding, and if he can get the materials I reckon that will be ample, and will give a suitable deck for light storage. He might want to do the rafters one day if he needs to hide up there.

[MATB1]

Ha ha thanks PJ! I was going to show him this but now I'm not so sure - don't want to go giving him any crazy ideas!