Roof joist insulation

Zither

Evening all!

Another question for you all if I don't mind!

I've just moved house and the loft is boarded out. There is insualtion under the boards (I don't know the type/age/depth etc at the moment). However, the space between the rafters is not insulated - there is just the membrane which the tiles sit on.

The loft is boarded out but currently only used for storage - it isn't a bedroom. So, would it be worth me, for the cost of materials, insulating the space between the joists as well? Would this help keep the house warmer in both summer and winter? Or would it only make a minor difference if we assume the existing ceiling insulation is of reasonable quality?

TY

zither

Doozergirl

You need a ventilation gap, so I would guess that's part of the reason it's there. I certainly wouldn't put anything down there in a willynilly fashion.

If it's over the rafters then it may well be solid insulation, which needs less depth than rockwool.

Of course we don't know, because we're guessing.

Zither

Doozergirl wrote: »

You need a ventilation gap, so I would guess that's part of the reason it's there. I certainly wouldn't put anything down there in a willynilly fashion.

If it's over the rafters then it may well be solid insulation, which needs less depth than rockwool.

Of course we don't know, because we're guessing.

Hiya - thanks! Totally understand the need for ventilation in the roof and appreciate not easy to answer with my vague description - unless I've misunderstood though (new to all this) I'm asking whether I should also insulate the currently un-insulated space between all the roof joists (save for an air gap between membrane and insualtion) or whether it wouldn't make much difference - seen as the floor of the roof already has insulation? Not sure if overkill, or?

Thanks!

ComicGeek

No, I can't see any benefit in insulating between rafters as well. Likely to cause problems with condensation. It would be overkill, and cutting insulation to fit between rafters is a pain.

Better to investigate what insulation is below the boards, and upgrade this if it's rubbish. I've installed Celotex PIR rigid boards below my loft boards, you can buy some cheaper seconds boards with only minor imperfections/damage.

Zither

ComicGeek wrote: »

No, I can't see any benefit in insulating between rafters as well. Likely to cause problems with condensation. It would be overkill, and cutting insulation to fit between rafters is a pain.

Better to investigate what insulation is below the boards, and upgrade this if it's rubbish. I've installed Celotex PIR rigid boards below my loft boards, you can buy some cheaper seconds boards with only minor imperfections/damage.

Ok great, thanks! How would I know how rubbish the existing insulation is? For example - aside from too thin/looking a big ragged - are there any telltale signs??

Thanks!

Z