I have a new 20'x7' shed which my wife will use as an artist's studio. The shed is heavy duty T+G. I want to insulate the walls and roof.
My local Sheffield Insulation Trade Counter recommends new-fangled stuff called "Frame Foil" stapled onto the uprights of the shed walls, with "moisture board" directly on top of that. But it will be pricy - I reckon about =A3600 for the Frame Foil alone.
How good is "Frame Foil"?
What alternatives are there? Preferably cheaper...
Could I use T+G pine cladding?
What gaps do I need between "moisture board", insulation and outside walls?
There will be a 5-socket ring in the shed. What is the best way to get the connections to the electricity sockets through any wall covering/plastic membrane/insulation?
I have a new 20'x7' shed which my wife will use as an artist's studio. The shed is heavy duty T+G. I want to insulate the walls and roof.
My local Sheffield Insulation trade Counter recommends new-fangled stuff called "Frame Foil" stapled onto the uprights of the shed walls, with "moisture board" directly on top of that. But it will be pricy - I reckon about =A3600 for the Frame Foil alone.
How good is "Frame Foil"?
What alternatives are there? Preferably cheaper...
Could I use T+G pine cladding?
What gaps do I need between "moisture board", insulation and outside walls?
There will be a 5-socket ring in the shed. What is the best way to get the connections to the electricity sockets through any wall covering/plastic membrane/insulation?
Have a look at Celotex and Kingspan. This is polyisocyanurate foam with foil front and back as a vapour barrier. 50mm would be fine for this application or thicker if you don't mind losing some space.
Yes
I did a similar project for a cabin. I put vertical studs of pressure treated timber fitted to the outside walls and 75mm deep. The whole inside was then sprayed with Cuprinol clear wood preservative - the solvent based proper one as opposed to the watery girls version.
The Celotex sheet was sandwiched in between and taped using the special foil tape, thus leaving a space of about 25mm between the backside of the sheet and the outside wall for ventilation. The same thing was done for the pitched roof. I had already done the floor by laying in Celotex on spacers before butting down the floor boards.
I then used a 9mm T&G cladding secret nailed to the studs (hint an air nailer is good here) and finally used a clear acrylic matt varnish (watery girls one).
I put in 20mm plastic conduit throughout for hidden sockets and ran PVC single conductors inside.
I then ran three compartment trunking around the whole thing. This allows for easy modification.
It's all surprisingly expensive. You need to learn what R,K & U values are about, then run the numbers (simple spreadsheet) to make any sense at all. Watch out, as most things are listed (on the web anyway) in US units for R value. Also look at finished costs, including battens, membranes and plasterboard.
K is an inherent property of the material. R is the overall performance of a wall component (one material layer), taking into account its thickness. You can get total wall performance by adding up the R for each layer (Big R is good). To a rough approximation, R for bulk materials (glasswool) is their thickness divided by their K. U is the reciprocal of R and you might see building standards for finished wall expressed in it (little U is good).
If you use SI units, that's it. If you use US units, there are screwy conversion factors everywhere.
For a material like Frame Foil or plasterboard that only comes in "finished thickness", then there's no K value, just one overall R.
Frame foil is deliberately designed to have an R value about the same as 150mm glasswool, a "typical" insulation level for walls.
What's good about it?
Thin. It's about 65mm thick overall - inch for the foil layer, 3/4" airgap either side. You _must_ preserve this airgap!
Built in vapour membrane.
Easy to install. Not so much bulk to worry about.
Resistant to cold bridging. You can squash it narrow without loosing too much performance and you can squash it entirely flat and still have a little. Compare this to glasswool against a stud where it tips away a little and leaves a gaping gap.
Easy to install, especially on walls.
What's bad?
Performance isn't quite as good as a really thick glasswool layer.
Easy to screw up the installation. Squashing it or not providing the airgap (use counterbattens before plasterboarding over it!) will produce a poorly performing wall.
Easily confused with "bubble" foils that only have about half of the R performance.
Bad reputation with some regulatory bodies, owing to inept testing methods a few years ago. Lots of people will tell you "it doesn't work".
Cost.
About the best (practical) insulation / thickness performance is from Cellotex etc. yellow foam rigid boards with isocyanate foam and silver foil faces. These are 65mm too, about the same as Frame Foil.
Cheapest (and perfectly good) is rockwool or glasswool of 150mm or so. Somewhat more labour to fit and it's two or three times thicker, which can be an issue for headroom in some retrofit locations.
Your price appears to be roughly =A310/m^2, which is slightly more than glasswool (by the time you've put plasterboard over it). Yellow foam is more than this, maybe =A315-20 / m^2 and the bubble stuff is half this, maybe =A35/m^2.
I use the foil on walls, because the ease of installation is useful. If I don't care about thickness, I'd go with glasswool. For retrofit insulation I'd look at the yellow foams, which I don't otherwise like owing to price and chemistry.
Thanks for the advice so far. A little more background:
The shed is already installed. It backs up against a rough stone wall i.e. I can't get behind it.
The internal wall battens are about 44mm thick, the roof battens about 66mm. I won't build out thicker than that or the shed will become too claustrophobic. What is the best insulation I can provide in those depths? I realise the shed will need heating in the depths of winter.
BTW the Frame Foil expert at Sheffield Insulation said it would be fine to put plasterboard directly on top of the foil i.e. no air gap on the internal side. Would you disagree?
Thanks for your advice so far. A little more background:
The shed is already installed. It backs up against a rough stone wall i.e. I can't get behind it.
The internal wall battens are about 44mm thick, the roof battens are about 66mm. I won't build out thicker than that or the shed will become too claustrophobic. What insulation can I use in those depths?
BTW the Frame Foil expert at Sheffield Insulation said it would be fine to put plasterboard directly on top of the foil i.e. no air gap on the internal side. Would you disagree?
No problem. Either foil, yellow foam or even (with a struggle) rockwool can retrofit from the inside alone.
If you're that tight for space, then by all means go with the foil.
I'd suggest attaching a "sub-batten" alongside the wall battens and stapling the foil down to those. You can get away without the full airgap, but you do need _some_ reliable airgap. If you have contact on the sides of the foil, then its insulation ability drops radically.
Yes. Of course you _can_ do this, but if you put pressure on the foil then it presses flat and turns into a cheap vapour barrier and no more. So don't do that.
If you can do it without putting excess tension of the foil _and_ without leaving the foil loose enough that it can flap around and rest on one of the inner surfaces .
On Thu, 24 Jul 2008 10:51:28 -0700 (PDT), a particular chimpanzee, Andy Dingley randomly hit the keyboard and produced:
Multi-foils have been caught out in recent years lying through their teeth about the performance of their materials. Some manufacturers have had it tested properly, and use resistance figures of ~1.7m²K/W; YBS I notice still quote the very discredited 6.1m²K/W. Real world testing has been done proving that anything more than 1.7m²K/W is bullshit.
On Fri, 25 Jul 2008 23:35:49 +0100, a particular chimpanzee, Andy Dingley randomly hit the keyboard and produced:
Actually, they have. One manufacturer (Thinsulex, IIRC) has a BBA certificate for their product.
You may be thinking of the discredited TRADA test. TRADA, who are UKAS accredited but not for insulation, certified Tri-Iso Super 9 as having the equivalent R-value as 200mm of Rockwool. Many in Building Control questioned the methodology of the test[*], but no-one seemed to have spotted that their certificate wasn't worth the paper it was emailed on.
[*] This involved two small 'rabbit hutches' in the south of France, one insulated with 200mm Rockwool, the other with Tri-Iso. The test reports said that both used similar amounts of energy to maintain the internal temperature, which therefore proved that Tri-Iso was the equivalent of 200mm Rockwool. What the report didn't say, and what TRADA refused to say when asked, was what the amount of energy used was. In other words, both 'hutches' could have been unheated.
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