attic insulation

tipperary

our new house will include an attic, which due to the roof pitch will not be suitable for suitable conversion to living accomodation. We would however be keen to use this space for storage. I am aware there are 'cold' attics and 'warm' attics. With a cold attic it is recommended to provide 150mm insulation between the joistsand similar again above the joists, with a danger of compressing the insulation when walking acrosss the attic. However I don't want to be heating the attic space unnecessarily. I am wondering is there any reason against placing some insulation between the joists, with the rest between the rafters, thereby leaving the attic space as 'semi warm'?

If the attic is ventillated then the effect of having a second layer of insulation will be largely lost.

Better to raise the floor to get in more insulation at this level.

bakerbhoy

You could go with rigid between the joists and insulated slab under thereby allowing the flooring of the attic space .

Smoo_D

I was at a trade show a few weeks ago, it appears a new form of insulation will be entering the market soon, get this, its made from grass. its a green material but unlike hemp and sheeps wool it does not cost 3 times that of kingspan. I am looking into it more myself as i am building a house and think im going to go for it, i will keep you posted with what i find out. Its called gramitherm, does anyone else know anything about it, it think its a company called bio refinery that is going to manufacture it

Mellor

It probably isn't as green as it appears, to prevent it roting its going to have to be treated with borax or similar. Its conductivity isn't as high as I thought. I would be concerned about it sagging though.

cubix

A bit like Tip I want to put T&G chipboard flooring in the attic purely to make it easier to walk around up there. At the moment there is just the standard layer of fiberglass up there between the floor joists. I presume like Tip said if I put my T&G straight over the fiberglass and screw it down to the joist there by compressing the FG I will lose any heat it is trapping. Can I use that Kingspan stuff, the foam with foil either side and use it instead of the FG and get the same results

Thanks Cubix

ardara1

cubix wrote: »

A bit like Tip I want to put T&G chipboard flooring in the attic purely to make it easier to walk around up there. At the moment there is just the standard layer of fiberglass up there between the floor joists. I presume like Tip said if I put my T&G straight over the fiberglass and screw it down to the joist there by compressing the FG I will lose any heat it is trapping. Can I use that Kingspan stuff, the foam with foil either side and use it instead of the FG and get the same results

Thanks Cubix

Hi Cubix - it would take at least 180mm of a single layer of Kingspan between only to do the same as two layers of total 270mm fibre - it'll cost a fortune and it won't work - you'll not be covering the thermal bridge thru' the joists. If you're only using the space as storage - DON'T - your heatloss will be the charge for the privlege of having storage space - compressed fibre only works to the thickness it's compressed to. (Buy a garden shed for storage!)

Mellor

Use battens to increase the support height in the area requires and fix flooring to these.
Layer the battens 90 degrees to the joists, and only in the areas required to access. Use OSB as a flooring material, chipboard isn't as good

cubix

Thanks everyone,much appreciated but a shame all the same;)