Suggestions for insulating a boarded loft

Dylan80

Our loft is boarded, with about 100 mm of insulation below. Due to difficulty of access to loft it is very unlikely we will ever use it. There are some areas where there is insulation between the rafters, but this is very DIY and will probably get rid.

Would laying an extra layer insulation over the boards work? What type of insulation would be best?

Grenage

It would work, but it's better if you can remove the boards. At my last place I removed there boards and put an extra 250mm on top.

BoxerfanUK

Grenage wrote: »

It would work, but it's better if you can remove the boards. At my last place I removed there boards and put an extra 250mm on top.

I may be missing something but why remove the boards? I would just lay insulation on top of the boards.

TheCyclingProgrammer

I too would just insulate over the boards. The wood has a u value too! As long as the insulation below is not compressed it should be well insulated if you add 170mm on top.

Mr.Generous

I'd be tempted to carpet over the boards next time your getting new carpets, insulation, wood, carpet - must be half decent insulation. You could always insulate over that if you really want to.

stator

Personally I'd replace the insulation under the boards with PIR board/celotex. I can't imagine not having a loft for storage.

The concern with leaving the boards in place is that they act as a cold bridge, transfering heat between the joists

Dylan80

Decided to insulate using 200mm blanket over the boards. Some quick questions:

1. As there is no felt on the back of the slates (1930s), does this mean it will be well ventilated?
2. If part of loft is not insulated (storage area), will this cause problems? Keep reading about condensation.
3. We currently have a glass loft hatch which gives light to our staircase, getting a new hole and hatch on Saturday. If we leave the old hatch, will this mean the insulation on the rest of the loft is pointless?

Cheers

MX5huggy

1. Yes it's well ventilated.

2. If you mean totally not insulated then yes condensation would be a issue. But keeping the existing 100mm under the boards will probably be enough to avoid this if you want to improve this put 50mm of celotex under or over the boards, it doesn't matter.

3. Don't understand how a glass loft hatch lets light in, every loft I've been in is very dark! But yes the hatch needs insulating an un insulated hatch, glass or wood will make as you say increasing insulation fairly pointless due to how u-values work.

Dylan80

MX5huggy wrote: »

3. Don't understand how a glass loft hatch lets light in, every loft I've been in is very dark! But yes the hatch needs insulating an un insulated hatch, glass or wood will make as you say increasing insulation fairly pointless due to how u-values work.

All the houses on the street were built with a skylight in the roof above the loft hatch.

Would adding a secured piece of perspex on the top side of the hatch be enough to insulate? Would hate to have to get rid of it.