Stephen wrote:
> Hello,
>
> I have a garage constructed of a single brick skin with a leaky roof
> (see flat roof post). I am thinking about insulating it with some
> Kingspan or Celotex. Would a 50mm thick sheet be sufficient if I fix
> it to all three walls and the ceiling or should I use a thicker sheet?
> Or is it a waste of time, after all, the fourth wall is not a wall at
> all but a door. Is any saving made by the Kingspan on three walls
> going to be lost due to heat loss through the door?
>
> Do I have to leave a gap between the kingspan and the brick? I thought
> I read on this group that I should leave an air gap? Would a gap of
> one or two inches be sufficient? Is this just to stop condensation on
> the bricks?
>
> I presume an air gap alone is not sufficient and that the gap requires
> to be ventilated? Would having it open at the eaves be sufficient?
>
> If I cover the Kingspan with plywood, would 12mm ply be sufficient to
> withstand knocks and would it support shelves, or would I be best to
> use 18mm?
>
> Thanks.

I did my garage/workshop by covering the walls with DPM plastic
sheeting, fixing 2x2 treated battens vertically with 1400 gaps, 8x4
sheets of 50mm polystyrene in the gaps and then 8x4 18mm shuttering ply
screwed to the battens (I trimmed the polystyrene slightly so it was
narrower than the ply). The thicker ply means I can screw almost
anything to it, almost any where.
I cut thinner celotex to fit the panels in the steel doors and stuck
them directly to the steel. A rubber wiping strip on the bottom of the
doors and some bits of rubber up the sides stop most of the draft.
I also cut polystyrene to fit between the rafters and just wedged them
in (but you need to fix your leaks first!).
I also put the boiler and DHW tank in the back of the garage, together
with a small radiator to heat the work area when needed.

So far it's been through one or two winters and has been successful

Dave

Stephen wrote:
> On Thu, 23 Apr 2009 15:35:50 +0100, NoSpam <(E-Mail Removed)>
> wrote:
>
>> I did my garage/workshop by covering the walls with DPM plastic
>> sheeting, fixing 2x2 treated battens vertically with 1400 gaps, 8x4
>> sheets of 50mm polystyrene in the gaps and then 8x4 18mm shuttering ply
>> screwed to the battens (I trimmed the polystyrene slightly so it was
>> narrower than the ply). The thicker ply means I can screw almost
>> anything to it, almost any where.
>
> Sorry, I am bit unsure why did you need to use DPM?

To reduce the moisture entering the workshop

>
> I notice you used polystyrene rather than kingspan/celotex. I thought
> realise that polystyrene is very much cheaper than celotex but I
> thought it was a much poorer insulator? 50mm of polystyrene would be
> equivalent to how much celotex? I won't have the advantage of a boiler
> and water tank, so I wonder whether I might notice the difference?
> Should I pay more for the celotex?

You need to get the thermal conductivity figures and do the sums to
decide whether the cost is worth the performance. I stumbled over a pea
processing factory that was being dismantled so the polystyrene sheets
were free.
>
> Polystyrene is also more flammable, so is that another good reason not
> to use it?

I tested it and it appeared to have a flame retardent in it, it burnt
slightly but then went out. It's down to cost-benefit again
>
> John seems to be able to screw anything to the 12mm ply he used, so I
> hope to use 12mm rather than 18mm, just to help keep the cost down. Do
> you think that would work as well as your 18mm ply?

Obviously it depends what you might want to fix to it and how it will be
fixed to the wall.
>
> Thanks again.

In message <(E-Mail Removed)>, Stephen
<(E-Mail Removed)> writes
>On Sun, 26 Apr 2009 10:46:22 +0100, NoSpam <(E-Mail Removed)>
>wrote:
>
>>> I notice you used polystyrene rather than kingspan/celotex. I thought
>>> realise that polystyrene is very much cheaper than celotex but I
>>> thought it was a much poorer insulator? 50mm of polystyrene would be
>>> equivalent to how much celotex? I won't have the advantage of a boiler
>>> and water tank, so I wonder whether I might notice the difference?
>>> Should I pay more for the celotex?
>>
>>You need to get the thermal conductivity figures and do the sums to
>>decide whether the cost is worth the performance. I stumbled over a pea
>>processing factory that was being dismantled so the polystyrene sheets
>>were free.
>
>I thought that would be a simple exercise so I went away to look for a
>web site listing u values. I've now got a headache!

The Celotex site has a calculator. You need to sign up and then remove
most of your security but it will give a printed result suitable for
presenting to building control.

regards

--
Tim Lamb

On Apr 26, 10:36*pm, Stephen <inva...@invalid.org> wrote:

> I've seen sheets of polystrene, kingspan, and celotex for sale in
> places like Wickes and B&Q.

You'll probably get more for your money here:

http://www.secondsandco.co.uk/

They've been mentioned on here several times, and I've used them and
found them fine.