# Loft insulation advice



## devonwoody (22 Nov 2013)

Recently done a living room refurbish, new ceiling boards etc.

The existing loft insulation (fibre glass upto 4" thick) was badly disturbed in places and I am wondering if this would be a good solution.

relay this on top of new plasterboards and then put firbreglass back on top.

http://www.diy.com/nav/build/insulation ... d=12108260

Anyone with experience of this product?

I don't want thicker insulation of 100mm because our loft is used for a lot of storage items and I do not want to part.


----------



## RossJarvis (22 Nov 2013)

devonwoody":2epzio5c said:


> Recently done a living room refurbish, new ceiling boards etc.
> 
> The existing loft insulation (fibre glass upto 4" thick) was badly disturbed in places and I am wondering if this would be a good solution.
> 
> ...



I fitted this for a friend on a dormer window, along with a new window. I found it fairly easy to use. It replaced fibreglass matting insulating the sides. They said the area was much warmer than before, however I can't say if that was the foil stuff or the other work "making good", such as double glazed window etc.


----------



## chippy1970 (22 Nov 2013)

That stuff appeared in the trade years ago and they said it would replace the usual celotex or fibreglass insulation in New builds . Well it never did as it was found out to be nowhere near as good as they thought. We still use celotex on all the new builds I work on.


----------



## devonwoody (22 Nov 2013)

Thanks Chippy, I suppose because I have a large amount of fibreglass insulation already, this foil insulation would still be an addition so I would not be losing effect but getting a plus.

However if the reflective foil is covered with fibreglass, perhaps it would do nothing?


----------



## RogerS (22 Nov 2013)

devonwoody":378bddgt said:


> Recently done a living room refurbish, new ceiling boards etc.
> 
> The existing loft insulation (fibre glass upto 4" thick) was badly disturbed in places and I am wondering if this would be a good solution.
> 
> ...



Useless, DW...a lot of building controls will not accept this stuff


----------



## No skills (22 Nov 2013)

I've got this under the floor in the front room. It did make a small difference compared to before installation but had I been more flush and better educated I would of used cellotex or similar. Hindsight, its great.


----------



## Lons (22 Nov 2013)

I haven't searched but the big sheds, B&Q and Wickes etc. usually have really good promotions an around this time of year on "top up" glassfibre so you would buy 180 or 200mm thick to bring it up to regs. I did this with mine a couple of years ago and it cost very little.

Bob

#-o Just read the rest of your post about not wanting thicker insulation


----------



## Jacob (22 Nov 2013)

Is no good I'm told. 
I'd put glass fibre between the joists, 3" celotex or similar over them with all the seams taped. Then 6mm plywood on top for light loading only. Loses 3" of height but good value insulation. If you can lose more space and get up to 12" celotex in this is worth doing.
Detailing important - pay particular attention to the joist spaces at the ends and sides, near the external walls or roof and pack them well so that the space can't get cooled under the insulation.


----------



## devonwoody (23 Nov 2013)

I would like to have thicker (and greater insulation) but I also must have the loft for storage use. 

How is this possible if insulation is above joists level?


----------



## No skills (23 Nov 2013)

Can you insulate the rafters instead? Maybe with the super quilt stuff?


----------



## devonwoody (23 Nov 2013)

No skills":2ksw4nvh said:


> Can you insulate the rafters instead? Maybe with the super quilt stuff?



Yes that's possible, I recall many years ago we had a newly built house where that was done, but these days of ventilated soffit boards I cant see the point.


----------



## RogerS (23 Nov 2013)

dw....I remember I used something very similar to lag a hot water pipe/joints/etc where normal pipe insulation wouldn't easily go. When I touch the outside of this foil, it is noticeably warm to the touch. When I touch the adjacent pipe insulation it is cold. OK...the foil stuff is better than nothing, I guess, but personally I don't think it worth the effort or money. Bit like double-glazing windows.....payback period measured in decades.


----------



## Jacob (23 Nov 2013)

devonwoody":2vckl513 said:


> I would like to have thicker (and greater insulation) but I also must have the loft for storage use.
> 
> How is this possible if insulation is above joists level?


Plywood on top of the insulation. Means you can store stuff but not a proper floor for regular use.


----------



## Lons (23 Nov 2013)

Jacob":p7zfltfk said:


> pay particular attention to the joist spaces at the ends and sides, near the external walls or roof and pack them well so that the space can't get cooled under the insulation.



You would need to check the method of roof space ventilation before doing that as if soffit type vents. Nothing wrong with what Jacob said except that the insulation must not block the ventilation path from the soffit, that would definately not be a good idea! Not an easy task to get that detail right in the restricted space available, especially for those of less than nimble ability or body larger than twiggy type :lol: 
Ventilation is a very important part of the construction and building regs - it's there for a good reason. 

Bob


----------



## devonwoody (23 Nov 2013)

Jacob":17ztdjfv said:


> devonwoody":17ztdjfv said:
> 
> 
> > I would like to have thicker (and greater insulation) but I also must have the loft for storage use.
> ...




Jacob I appreciate what you are saying but to walk across the loft on top of the plywood would compress the insulation down and also then press the plasterboard ceiling down because of the weight pressure. At present I walk on joists and avoid the bits inbetween. Your systems would require packing with timber to the top of insulation level?
Or what do you suggest.


----------



## Jacob (23 Nov 2013)

devonwoody":12xrghmg said:


> Jacob":12xrghmg said:
> 
> 
> > devonwoody":12xrghmg said:
> ...


3" thick celotex/kingspan etc is a fairly stiff board and you'd span it over the joists not between them, but would need ply on top to take any weight. It wouldn't take a lot of weight but enough to support the typical loft stored bits and bobs of furniture and stuff that nobody really wants and would be better chucked out!


----------



## devonwoody (23 Nov 2013)

Its getting to the cold water tank (for maintenance), its nowhere near the loft opening.
These are some of the problems with this increased insulation. Storing your three holiday suitcases etc. I do not have the space in our home, that's what I use the loft space for etc. 

I think I will have to pay the energy company and suffer the loss and not have that extra insulation.


----------



## Jacob (23 Nov 2013)

devonwoody":6n3psfhd said:


> Its getting to the cold water tank (for maintenance), its nowhere near the loft opening.
> These are some of the problems with this increased insulation. Storing your three holiday suitcases etc. I do not have the space in our home, that's what I use the loft space for etc.
> 
> I think I will have to pay the energy company and suffer the loss and not have that extra insulation.


You could walk on the ply no prob. It's just not strong enough as a proper floor for everyday use. So suitcases etc access to the tank no prob. The tank would want boxing in with insulaton over/around but not under it.


----------



## axe (23 Nov 2013)

Not sure if you can afford to lose the headroom but you could use this -

http://www.loftzone.co.uk/storefloor.html


----------



## MMUK (23 Nov 2013)

One thing to remember, and this is extremely important, if you have any cables in the ceiling void you must leave an air gap around them. Try pinning cables to joists wherever possible and leave an insulation gap of at least 1 1/2" around the cable. If you pack insulation tight to the cable, especially fibreglass, you could end up with a fire.


----------



## whiskywill (25 Nov 2013)

What about these? http://www.toolstation.com/shop/Access% ... 303/p44016


----------



## KevM (25 Nov 2013)

I used some of those Toolstation loft legs - they worked fine with chipboard flooring.
Would I want to clog dance on the finished result? No. 
Do they act as a safe base for the odds and sods that I'm waiting 10 years before throwing out? Yes.


----------



## mind_the_goat (25 Nov 2013)

You could raise the height of the joists by pinning some 4x2 (or whatever size you need) on top, then put your existing flooring on that.


----------



## scholar (25 Nov 2013)

DW

I have had similar issues and have looked at many solutions - I rejected all of the foil products, not because they don't work (in fact I think it would not harm as an additional element in the way you have suggested installing it), but because they can interfere with aerial reception and I have loft aerials.

What I used is this stuff (it's not that cheap, but I was lucky to find a big quantity being sold as surplus on eBay - it was a fairly hilarious sight carrying it all home on top of the Land Rover roofrack, easily doubling the height...)

http://www.space-insulation.com/product ... board-eco/ 

I think these are branded slightly differently to the boards I have been using, which I recall was branded Polyfoam - same stuff. The blurb on the link suggests various methods of installation, but what I have done is 100mm fibreglass between the joists, then 50mm Polyfoam on top of the joists and then 18mm t&g chipboard on top - the Polyfoam just sits in place and the chipboard is screwed to the joists through the Polyfoam (ends of the Polyfoam are cut to sit on a joist, but this is not necessary with the chipboard). 
It all feels very strong and overall is a good arrangement - it is more work than most people would want to put into insulating their loft.... But it was the best technical and practical solution I could find.

NB the point about the wiring is important - I have rerouted stray cables into a logical grid either running down the sides or in surface trunking, except in a few areas where this would be annoying - here I have cut a channel for a suitable sized trunking to be let into the top side of the Polyfoam - this is only for low current circuits eg a single light fitting.

I have not compared the compressive strength qualities of Kingspan etc to the Polyfoam, but if it is at least as strong, it would be a good alternative I think (although bear in mind that Kingpan comes in 8x4 sheets, whereas the polyfoam is 8x2. 

Polyfoam also makes a good sacrificial cutting surface for cutting sheet materials....


Cheers


----------



## beech1948 (25 Nov 2013)

DW,

Is there any way you can produce a wood based floor riser say 8 inches high, floor with chip board etc. Some of ones suggested are simply plastic so moulded and wood is stronger and easily shaped and fastened.

I think polystyrene is a fire risk and should not be used. Burns/ignites quickly and when molten drips fire down on everything. Ask the fire brigade advisory staff.?

regards
Alan


----------



## RossJarvis (25 Nov 2013)

I've spent a fair bit of the past few weeks walking about on unprotected celotex, placed on a concrete floor. Then someone bunged 5 ton of screed on it. If it's fully supported and doesn't have a high "point load". It seems to take a fair bit of abuse. Of course, ply over the top would make it much more robust. I can't stand the fibre-glass wool stuff, particularly laying it. It also acts as a perfect sponge to soak water up and rot stuff which the foam board doesn't.


----------



## devonwoody (26 Nov 2013)

Thanks to those latest responses, should be a solution there.
Have to have a word with an electrician and find a way to reroute wiring, mainly lighting, but there is a 6mm cable to a shower and also to the workshop up there.

Also when we have to replace the boiler it is going to have to go up in the loft on an outside wall and that will need a pathway up there.


----------



## AndyT (27 Nov 2013)

I went through a similar exercise and ended up with a hybrid solution. In the full height area where we need storage I left existing fibre between the joists and put closed cell boards across, with chipboard loft panels on top, screwed down with long screws. In the inaccessible parts I just topped up the fibre. But it was a fiddly, horrible job to do. I know that you won't get anything like it on the subsidised free insulation schemes, though they can at least mean that the materials are cheap to buy. And I did reroute all the cables to run above the insulation.


----------



## morfa (27 Nov 2013)

I got some 2" by 8" joists and put them at opposite angles to the existing joists. Used metal plates to join them to the existing joists. They're about 400/500mm apart, plonked standard loft insulation over the top and then I've got normal loft flooring over the top of that. Cost me about £300 for the various materials all in.

You've all got me worried about the cables however. I've just got standard mineral wool loft insulation and it's not compressed, just laid loosly over the existing insulation (and cables). It's been in a year and the house hasn't burned down (yet). Is it worth getting the sparky in to lengthen the cables to they run over the flooring?


----------



## AndyT (27 Nov 2013)

An answer on cables from a non-electrican. When I looked into it to do mine, I found the reason for keeping cables clear is this. Cables are sized so that when carrying working current, they can safely lose the heat produced in the conductors. If you prevent a cable from cooling, by covering it in insulation, the Max rated current reduces. Similar downrating applies if buried in plaster. I looked at the total load on the loft cables and since they all now connect to low energy lights not 150W bulbs, the total is tiny. So it would be fine to cover them. But I played safe in case a future owner wanted to do something different.


----------

