Encapsulated loft insulation

[Theo]

I'm looking for fibreglass loft insulation that comes wrapped in a plastic wrapper, to prevent the installer having to handle the fibreglass. This is for two reasons: one is the loft is very awkward to work in, so it's hard not to come into contact with the insulation, and the second is the cat likes to go in there if somebody left it open, and she then licks all the fibres off herself :(

The popular brand is Knauf 'Space Blanket' which is only sold in the sheds, but nobody seems to have any stock of that (Wickes has a few rolls in random stores but not for delivery, and at 3x the price of un-encapsulated). I came across another brand called 'Super Loft Blanket' from a company called U-spec of St Helens, but their distributor appears to be out of stock too (in the 170mm thickness).

Are there any other brands or sources of this stuff?

(The alternative no-itch product is polyester fleece, but the nice thing about Space Blanket is the wrapping is supposed to be silvered mylar film to reduce thermal radiation - kills two birds with one stone)

Thanks Theo

[alan_m]

Although not ideal for the cat IMO rockwool is a lot better than fibreglass. You can also get real wool insulation but more expensive and you need a thicker layer.

Most of the insulation in my loft is rockwool but where I laid down some boards to give access to water tanks and TV distribution boxes I have some Space Blanket insulation on top of the boards which can be easily moved to one side when I need to go into the loft. From memory, it was around x2 to x3 the price of un-encapsulated even in "more normal" times (per unit area/thickness) I doubt of the metallised layer adds anything to the effectiveness of the insulation

[John Rumm]

There is a Knauff product called Eko roll - made from recycled materials but treated in such a way that its soft and non irritating to handle, and does not make any fine floating fibre dust. Its not an encapsulated product though.

[Theo]

Thanks. I saw that (seems to be the new thing the sheds are touting) but I can't seem to find a datasheet for it anywhere. B&Q/Tradepoint links to a minimalist Declaration of (fire) Performance that admits 'Wickes Loft Roll Combi Cut', 'Eko Roll' and 'Space Combi' are all the same thing, but they're also shed-only brands with no information.

I assumed fibreglass, glassfibre, glass wool, mineral wool, Earthwool and Rockwool (trade names) were all the same thing, or are there differences in composition between the brands?

Theo

[John Rumm]

Those are one class of product...

and those a distinct separate one IIUC.

Then there is another class of products that has additional sound deadening properties.

There seems to be a different "binders" used to stick them together, I expect the various shed brands like the Eko wool all are variations of:

(I used the B&Q one when I did my bathrooms a couple of years back - there was an area of ceiling void that was uninsulated, so I picked up a couple of rolls of the Eko roll. It was definitely noticeable that it was much much nicer to handle than normal glass wool)

[John Walliker]

I laid a few rolls of this (the 170mm thick variety which comes with partially cut widths for 400 or 600mm joist spacing) recently wearing gloves and a facemask but with bare arms which occasionally came into contact with it. I was pleasantly surprised not to have any itching afterwards. There was very little airborne dust.

John

[Dave Liquorice]

But very nice to handle and no irritating fibres or dust. It does shed fibres though.

ICBA to do the research/maths but above 8 to 10 inches of these forms of insulation you get into the releams of diminishing returns. We've got 4" of real wool but under 22 mm chipboard which also has some insulation value. An IR thermometer tells me the ceiling is the same temp as the external internally insulated with 50mm celotex walls and an IR camera showed the the same. Internal plasterboard walls are at most 0.5C warmer...

[Theo]

It seems prices are pretty constant across suppliers. According to my calculations:

Mineral wool: £3/sqm (200mm thick) Encapsulated mineral wool: £10/sqm (200mm thick) Polyester: £14/sqm (200mm thick = 100mm@£7x2) Sheep's wool: £13-18/sqm (150mm thick)

I probably have 50sqm to do plus some walls, so that's quite a price jump.

It's currently 4 inches, dropping to zero in some places. Thermal camera photos aren't terrible, but interested in blocking solar gain as well as heat loss.

Theo

[Theo]

Interesting. It seems they still recommend gloves but it's less scratchy. Perhaps I should grab some rolls from Wickes and give it a test...

It appears their contractors' version (Earthwool Loft Roll 44) is made of the same stuff and that's readily available.

In other news, what would the team recommend for insulating the rear of vertical stud partitions? There's already fibreglass insulation, but the back of the studs is exposed? If I were to pin some Celotex to it I'd compress the wool in there. I don't think rockwool is good for vertical surfaces, especially not strung horizontally?

Theo

[PeterC]

Some heat is lost by convection causing percolation throgh the insulation; the chipboard will stop this. Since I boarded about 70% of the loft I'm very careful with vapour and use the extractor in the bathroom for the obvious reasons and also for about 40 min. or so in the morning.

[RJH]

Reading this, I'm not sure why you don't just celotex the ceiling (and verticals) with, say, 75mm. You could loose board over too, without the need for stilts over wool etc. If I had my time again it's what I would have done.

[Andrew]

102 uses for many dead cats ?. (Loft insulation). :-)

[Andrew]

Be careful with sheeps wool. It is supposed to be treated to kill any possible parasites, but there have been incidences where people have used it, with good intentions inside walls of super-insulated new builds and the treatment was either not done, or ineffective.

Don't overlook PIR , 'Celotex'. Unless you have a lot of aluminium or magnesium up there, a domestic fire won't get up to the temperature where PIR actually burns.

[Theo]

Hmm, that is a good thought. I had previously looked into using EPS-backed chipboard, but there's no a lot of available products and reckoned it would be easier just to lay rolls on top.

I hadn't considered replacing everything with celotex. I can see that has merits. One issue is the space - no part of the loft is more than 4' high and the roof slopes from 4' to 0', so it's not much fun to work in there. Access is also awful (can't get large items through, very limited turning circles). Cutting celotex is a bit of a pain too. I had hoped throwing some encapsulated rolls down would be least-work.

A second concern was that installing foil-backed insulation is likely to make RF conditions worse - mobile signal and wifi. But that's likely the case with any insulation to block solar radiation, which is a big issue. The second can be addressed with more access points, I could probably live with worse mobile signal. So I should probably stop worrying about this and go with the flow.

However losing some of that height for insulation would also be a pain and celotex has advantages here.

I might think about a mixed strategy: replacing the tall parts with celotex and boards on top and the awkward bits with rolled insulation. Probably put celotex behind the batts on the existing stud walls too.

Methinks I should go and grab some samples to try...

Thanks (and to RJH too) for a good idea :)

Theo

[The Natural Philosopher]

???

Yes foil in walls messes up inter room wifi and makes mobile coverage strange but foil in ceilings is a different matter. You aren't receiving signals in that direction except GPS, so your phone wont know where it is when it's at home...

..and as far as solar radiation goes, what on earth are you talking about? cosmic rays? Curiously the fact that its dark in a loft is a fairly sure sign that all incoming solar radiation is stopped by the roof...not by any insulation thereafter.

[charles]

Depends on how high up the mobile phone mast is in relation to your house

That's the visible radiation. gives no indication of other frequencies, If you logic was correct, there's be no heat loss through roof tiles.

[Andrew]

Sharpen the back of a hacksaw blade into a knife and make a handle for it. AVoids sawing and creating lots of dust. If you get the sharpness right and pull it through at the correct angle it just slices through PIR up to 70mm thick.

[T i m]

<snip>

Ignoring the cats for a second, do you know you are allergic to contact with fibreglass or is it just a precaution (in case you are or for some other reason)?

I know I'm not allergic to it and have often been amongst it (inc insulating my loft) with no obvious ill effect?

Maybe if one can build up a tolerance of such things I did when I was shoved into small lockers and under-deck spaces fiber glassing over wooden pads for cleats and the like on Dads various boats when I was a kid. ;-)

Cheers, T i m

[RJH]

I thought the main danger was inhaling the glass fibres/dust?

[T i m]

<snip>

I think you are right (medically) typically re insulation materials and if sanding or grinding (fiber)glass reinforced resin, but I'm also aware that some can quickly come up in a rash or itch if they simply come in contact with it (I don't).

Mum is allergic to Guinea pigs (their fur, not eating them) but nothing else (that we know of).

Cheers, T i m