Underfloor insulation

Claireful

Hi,

I am renovating my 1930's bungalow and was looking to insulate under the floor boards when lifting all the floors. I have been using a foam which I think is called Kingspan but is very expensive. Does anyone know of a more cost effective way of insulating underneath the house. I have seen on tv shows where they have used a substance that looked like chippings which were used in a net. Also is it really worth the cost of insulating under the floor or should I just lay moisture board over the beams underneath and forget about the insulation
.

Thanks for your help.

mart.vader

Hi,

I suggest Rockwool between the joists, held up by netting if necessary. Rockwool is cheap at the mo'

http://www.just-insulation.com/rockwoolcavity.html

the "chippings" that you refer to might be Vermiculite, but I don't think this is particularly suitable for underfloor, as you would not be able to use netting, unless the holes were very small.

brig001

+1 to Rockwool or similar between the joists. I have held it up with netting and fabric (garden weed variety) and had good results. I also sealed the floorboards to the skirting boards, and any holes for radiator pipes etc.

HTH,
Brian.

Claireful

Thank you that sounds a much cheaper option. Do you know if this would comply with building regulations. Also where do you buy the netting from?

chiefgoobster

Claireful wrote: »

Thank you that sounds a much cheaper option. Do you know if this would comply with building regulations. Also where do you buy the netting from?

You can get netting from any of the big DIY stores....I'd say a garden centre may be a tad expensive...or try Ebay.

brig001

Claireful wrote: »

Do you know if this would comply with building regulations.

Unlikely. I have only ever used 75mm thick batts between the joists, and if you wanted to do more than that, I would get specialist advice. I believe that increasing the insulation further can cause condensation the ends of the joists making them rot. Someone qualified in this area could do a proper condensation risk analysis and make recommendations - this gives you some idea of the potential problem http://en.wikipedia.org/wiki/Interstitial_condensation It may well be that something as simple as a VCL (vapour control layer (plastic sheet) ) under the boards and tucked behind the skirting would suffice, but I would check with a professional first.

HTH,
Brian.

Claireful

Thanks I am concerned about moisture being trapped and it causing dampness and rotting the joists and obviously I dont want to create a long term problem. The foam insulation is so expensive and costs more than the moisture board and laminate put together. At the moment I am tempted just to forget the insulation altogether and replace with moisture boards and laminate. At least the flooring will have a proper air flow circulating through it. It is difficult to work out whether the insulation will save enough long term to repay the cost. At least if the floorboards are removed no draft should come up into the room.

brig001

You have your priorities right - make it draught-proof first. If it were mine, I would still be tempted to put some Rockwool under there, or even fibre glass loft insulation - maybe separate it into two thinner layers. This might be messy, won't deaden the sound as much as Rockwool, but it is cheap.

ListysDad

Simple fact of the matter is that kingspan et al, properly fitted, will save you far more in the long run than less efficient rockwool.

Whilst it does cost more to install up front, energy costs are going up faster than the Empire State Buildings lifts so better quality insulation fitted now will save you shed loads down the line.

Being skinny now will cost you thousands long term.

As always it's your choice.

27col

You don't actually need netting, you can achieve the same effect by just stapling string to the underside of the joist. This would be easier to handle, because you could do it all from above. With netting you would probably have to get below the the floor to staple it in place.