Hi my loft is currently insulated with 4 inches of fibreglass and floored using chipboard flooring. There is also a lot of junk in the loft. Would I save a lot on my gas heating if I was to lay another 4 inches of insulation loose on top of the flooring?
Thanks Tricia
Not enough to cover the cost of a skip for all the junk! :)
Try calling your gas supplier and asking them what they would recommend, they are likely to have all sorts of information regarding this... their website might offer some advice.
I do believe that 4" is the norm as this is the height of the joists in most lofts, however there are now many products on the market which offer much higher insulation ratings within a 4" void than the age-old fibreglass, but they are more expensive and some calculations would need to be made for your particular situation before the cost could be justified.
HTH deano.
The message from "Tricia" contains these words:
Probably, but if you're going to be posh about it, empty the loft, raise the floor (I used 4x2s across the existing ones), fill, then replace the floor.
I know - I did it a couple of months ago.
Grants are often available for this sort of work. The wife gets mobility allowance so we got ours free.
You are unlikely to save a "lot" - obviously you will save something.
Much depends on where your house is least energy efficent. If for example 95% of your heat loss is through drafty windows, poor fitting doors, or uninsulated solid walls, or a grossly inefficent heating system then you would get better return for you money by fixing the most expensive source of heat loss first.
One way to assess the situation is to go round doing some heatloss calculations for the house. If you find that the loft does account for a significant proportion of the loss then you have your answer.
Not if its really covered in junk. Good insulation, is junk...;-)
|Hi my loft is currently insulated with 4 inches of fibreglass and floored |using chipboard flooring. There is also a lot of junk in the loft. Would I |save a lot on my gas heating if I was to lay another 4 inches of insulation |loose on top of the flooring?
Ours is boarded in the middle, covered in heavy junk and double thickness insulation round the outside, where were store the light junk.
Ah a sensible answer! All this "stuff *more* insulation in the loft and you'll save money" is a bit of a con (IMHO). There is a large saving to be made going from nothing to 4" and boarding but the returns after that are really not worth chasing in a "normal" house IMHO. You would have to live in a hermetically sealed house with draught strips on all the doors (which were always shut) for the effect to be noticeable. Most people like to breathe however and tend to leave bedroom/bathroom windows ajar for ventilation and go in and out of the house through the doors. Once you do that, *extra* insulation in the loft becomes pointless.
There are foolproof ways of saving money (some as mentioned by John):
Turn the thermostat down and wear warmer clothes. Get thicker curtains for the living areas. Use TRV's or zoning so that only the sitting room (for example) is toasty and other rooms are colder. Get a more efficient boiler (long payback time though).
A good test for the roof is during the winter. If when most houses have snow on the roof yours hasn't you really are in trouble heatloss-wise through the roof!
John, I recently had 250mm installed via a grant and £ 100 cost to me trouble is, they layed 100mm inbetween the joists then 150mm tangental to that (if thats a word?) Can I move the top layer round, push it in the joist gaps and board it ? or am I spoiling the effectivness of the insulation by crushing it ? TIA
Well, I wasn't John, but yes you will spoil the effectiveness by crushing it - worse it will be less effective than the 100mm that was there before (less trapped air)! All you can do is raise the joist height by adding wood. Personally I wouldn't bother - if you are going to board it stick with the
100mm, the board will add a bit. Where it's not boarded leave the orthogonally (rather than tangentially!) laid strips in place.
Yes. It is the physical height of the material that provides the insulation. By crushing it down from 250mm to 100mm, you are losing at least that much in insulation, probably considerably more.
Your alternative is to place additional joists (preferably at right angles to the existing) and board over those.
Better still is to insulate the rafters instead. This has the advantage of providing a warm loft, which is better for storage. However, the insulation scheme must be properly designed to ensure that there are no damp or ventilation issues.
Christian.
What the others said! Another option would be to get some ridgid board insulation like celotex or kingspan (or better still one of the cheaper alternative suppliers of PIR foam). Where you are going to board, remove the top layer of fibreglass (you can stick that on the unboarded bits), lay down the insualtion, and board directly on top of that. When fixing the boards just screw right through the boards and insulation into the joists.
Now that's a damn good idea - wish I'd thought of it! I would guess almost no loss of insulating properties as Celotex + board would be roughly equivalent to 150mm loose fibre.
You need to board under it as well. It isn't very strong and the joists would crush it when you walked over it. If entirely boarded underneath, then it would be strong enough.
Christian.
IME If the existing joists are 2" wide then you won't need any boards under it. It would end up being like most warm deck flat roof designs, and you can safely walk all over those without any problem. PIR foam is hard to crush unless you have an exposed edge you can stand on.
I was going to add that the weight on the ceiling joists would prolly be far too much with double boarding, but I guess you could get away with a much thinner sub-board and a thinner top board too.
One thing I can;t get my head round is how you get 1.8 x 2.4m sheets of ply/cellotex etc up through the loft hatch!
I'm surprised at this. Nice to know. It could save a lot of work next time I'm boarding a loft.
Christian.
I found with the boards I had (Ecotherm) you could safely stand on one without making any real depression in it, as long as you had your foot flat on it. If you stepped on an edge or corner you would crush it. With things like the dormer flat roof I used 80mm foil covered insulation boards laid directlyon the firrings, and then put 18mm ply directly on top. Then screwed through the lot with a few hundred 5 1/4" X 12 screws (paying particular attention at the edges of the ply to make sure there was no possibility of differential movement between the board edges which could damage the roof felt later when you walk on it). Even torquing up the screws to fully countersink them into the ply did not cause any real distortion of the insulation - perhaps one or two mm of localised depression.
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