insulating single skin brickwork

[chasfromnorfolk]

Can't see exactly this in previous posts... advice please on alternative ways of bringing a single skin brick detached garage wall up to current "habitable" building reg standards. I followed up a useful Knauf link from these pages and spoke to their technical guys who have suggested 140mm studs, 140mm foam and 12.5 foil-backed plasterboard - but that knocks a considerable amount off available floorspace from a single garage!

I'm reluctant to consider external solutions - is there a more "compact way" to do the job?

Cheers,

Chas

[A.L.]

I'm reluctant to consider external solutions - is there a more "compact way" to do the job?

- not for an economic cost, incidentally the U-value is about 0.24W/m²°K

[Barrie]

Are you able to do anything with the external wall?

Would an insulating render be possible?

Other brands are available....

http://www.thermakote.com/products/building-products/insowall-eco-insulating-plaster.html

[biff]

hi chas,
       i guess you will only reap what you sow but a few years back i did a job for a friend,i drylined his garage,
   we hung a vapour barrier from the wallplate right round the garage,
  then we rawplugged tanalised 2 x 2 battons onto the wall at "16 centres
  we cut the kingspan sheets to fit between the battons
 and cladded the lot in foil backed 12.5 plasterboard.
    the vapour barrier which hung from the wallplate also came out onto the floor a good "12 right round,
  we then laid 1200m heavy duty visqueen on the garage floor,fired down runners at "16centres and again filled in between with kingspan. we floor the lot with an 18mm ply,taped the joints and rolled out a wood paterned vynl.
 it was quick and neat and the finished job(taped and skimmed joints) presentable.it is now used as an office and he says it is the easiest heated room in the place.it is not passivehause but a massive improvement.
                                                                                               biff

[Baz]

What insulation material was the Knauf proposal. It looks like rockwool for economy but polyurethane like Celotex or Kingspan would be better. You can probably get away with 50-75mm of that but if the room is actually going to be heated a lot like an office it would pay ie save to go with 6 in of Celotex.

[Baz]

This site has some interesting stuff.
http://www.woodsinsulation.co.uk/Building_regs/pdfs/PART%20L%20PAGES.pdf
You need an absolute minimum U value of 0.35 to scrape through building regs.

WRT Biff's suggestion you need a breather membrane on the outside for walls not solid and tape up the foil plasterboard joints to seal.

[pb]

This site has some interesting stuff.
http://www.woodsinsulation.co.uk/Building_regs/pdfs/PART%20L%20PAGES.pdf
You need an absolute minimum U value of 0.35 to scrape through building regs.

That's not quite true; there are some weasel-words in the regs which permit a lower standard in some cases.

Document L2B (existing buildings other than dwellings, which is probably the one that would apply here) says that walls with internal or external insulation should be 0.30W/m2K or better "provided this is technically, functionally and economically feasible".  (Their test for economic feasibility is a simple payback period of 15 years or less and they state that, for example, a loss of more than 5% floor area would count as not functionally feasible.)  If it isn't possible to get to 0.30W/m2K within those constraints then the regs say that you should just do the best you can, though there is an expectation that you should be able to achieve 0.70W/m2K or better in almost all cases.

All that said, building regs as such don't apply to small detached buildings so long as they meet certain criteria, and your garage might well fall into that category.  If you're just interested in making the space heatable to use it as an office or something then you would probably find that lining it with 50 or 75mm PIR or similar would be sufficient.  (See e.g. Knauf Thermal Laminate Phenolic or BG Thermaline Super.)  You can trade off thickness for cost to some extent: if you use cheaper insulation (e.g. rockwool, EPS) then you need more of it for the same effect.

If you do need to get it passed by building control for some reason then your best option is probably to talk to the BCO and see what he thinks.  My general experience has been that they aren't actually all that fussed about exact U-values for anything other than new build and, so long as you can convince them that you are making some kind of effort to be reasonable, they will probably be happy.

[chasfromnorfolk]

As ever, thanks for all input - I'll cover further points raised:

A.L.- not for an economic cost, incidentally the U-value is about 0.24W/m2°K well, it certainly has the performance then

Barrie - we don't want to change anything externally

Biff - i guess you will only reap what you sow but a few years back i did a job for a friend,i drylined his garage... just what I would have done Biff, though Knauf's 140mm is a bit of a mystery, I think (like Baz suggests) it's a rockwool or something similar

Baz - I'm drawn to space-saving foamboard rather than  the Knauf 140mm of whatever...but 150mm of Cellotex would require the sale of a kidney as well as being bulky....
While not challenging, but for my education:WRT Biff's suggestion you need a breather membrane on the outside for walls not solid and tape up the foil plasterboard joints to seal?
Surely, with the foiled pb and taping plus foiled Cellotex (both impervious) providing something permeable against the brickwork is a bit superfluous as nothing will get through from the inside with a need  to escape, and you do want to keep the potentialy damp brickwork very much outside...

PB - interesting Regs caveat, and refreshingly practical of them... I seem to remember something similar in the upcoming April heat initiatives, along the lines of "insulate...where practical".
I'm drawing towards 100mm of Cellotex. It's to make a studio/office from the garage, so not likely to excite BC.  I wasn't planning to ask them and risk paying a fee, though since starting this thread today, the Chief Designer has already escalated things to include a toilet - so it may all go expensively kosher after all.

So what about this breathable / poly liner question then?

Chas

[bxman]

have a look at
http://www.proctorgroup.com/products/thermal

I am told it is quite pricey and those that know more about insulating properties will be in a position to recommend what thickness you should choose . Good luck and let us know how you get on.

[Baz]

You're right about the brick being damp. Celotex isn't totally waterproof and does absorb a bit so I'd put in the membrane to discourage it from working inwards before it has had time to evaporate. It isn't shown on most internal insullation diagrams though so I was rather reacting to Biff's suggestion and not wanting you to trap moisture between to layers (foil and plastic).

New build regs have traded specific values for a whole house concept so you can trade one bit off against another and without getting into details about those options I figured the 0.35 min would avoid a disaster of under specifying it and landing in planning trouble but not sure how much less a conversion allows.

for the wife: http://www.busyoutdoors.com/portable-toilets/c61

[pb]

have a look at
http://www.proctorgroup.com/products/thermal

I am told it is quite pricey and those that know more about insulating properties will be in a position to recommend what thickness you should choose . Good luck and let us know how you get on.

Not quite sure which of the Proctor products you were thinking of there.  If you mean Spacetherm then yes, it is extremely expensive and probably only a sensible proposition where thickness is the overriding concern.  I do have a couple of timber doors at home with spacetherm laminated inside the panels, where it seems to work well enough, but I wouldn't want to try to line an entire building with it.  It would probably be cheaper to knock the building down and start again on a slightly larger footprint than to insulate the whole thing with Spacetherm.

The Proctor "Retrophix" line is similar to the BG and Knauf laminates I mentioned earlier (i.e. dry lining board bonded onto Celotex-type insulation), except with Fermacell rather than plasterboard.  Fermacell, again, is a fine material (and most of the walls in my house are made of it!) but it might be overkill/over-priced for the case at hand.

[Eleanor]

Out of interest any idea of rough cost per m2 for Spacetherm? We just need a few m2 for insulating dormers. Thanks.

[wookey]

I'm doing my garage at the moment. 100mm PIR on the walls, 50mm XPS on the floor. That's not unreasonably expensive. The wall/floor covering cost about the same as all the insulation (multipro boards).

I've got 42.5m2 of wall to do and 21m2 of floor.

30 sheets of 50mm PIR (recticel) cost £567 (inc, delivered) from minster insulations.
28 boards of sirap gemmatherm XPS cost £214 from Green Footprint Solutions. (shop around for this stuff - that less that half the first quote - for cellecta X2i).

The technique is vapour (but not airtight) barrier on external walls (roofing membrane from screwfix). 50mm PIR glued to walls with PUR foam glue. All seams taped and joined to plastic sheeting on floor and to roof airtightness layer.
50mm timber battens on top, 160mm m10 frame fixings through to walls, with 50mm PIR in between. 9mm multipro boards on top (OSB would be a lot cheaper but not such a nice surface, nor fireproof). U-value 0.2.

Floor is 1000guage DPC on the concrete, tescon taped to wall insulation airtightness layer, 50mm interlocking XPS, with 12mm multipro magnesium oxide board for fully-floating floor. I'm not quite sure what the U-value of this ends up as, but it's only about half as thick as is required for U=0.22, so it'll be around U=0.36 I guess. I'll be putting some UFH pipe in the floor too.

The floor insulation depth is compromised in order not to make the doors so low that people bang their heads.

The wall construction is done like that so as to provide strong walls I can hang lots of workshop shelving off. If you don't need that you could just use 100mm PIR and no timber which would save a lot of faffing.

[JohnS]

Out of interest any idea of rough cost per m2 for Spacetherm? We just need a few m2 for insulating dormers. Thanks.

Eleanor

Proctor's have an online shop on their website.  http://www.proctorgroup.com/shop

1200mm * 1200mm * 10mm is £61.82 inc VAT ex delivery.

That is approx £43 per sq m.

John

[biff]

hi wookey,
         that should be an exellent job,i would not worry about the thickness of the insulation on the floor,i have done this floating floor dozens of times with fantastic results,,the chill disappears immediatly.
                                                                   biff