Insulation, what should I get

[timothyedoran]

What insulation should I get for my workshop. 4m X 3m

Polystyrene sheets @ 75mm would cost about £200
Celotex type stuff in seconds quality would cost about £400

I know that the celotex is about twice as insulting, but would I ever notice the difference?

Comments gratefully received.

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[9fingers]

What insulation should I get for my workshop. 4m X 3m

Polystyrene sheets @ 75mm would cost about £200
Celotex type stuff in seconds quality would cost about £400

I know that the celotex is about twice as insulting, but would I ever notice the difference?

Comments gratefully received.

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Be aware of the flammability of polystyrene and the resulting fumes.

Whether you need the extra insulation is complicated.
If the shop is going to be very well sealed and you are going to heat it and be in there long term then you will possibly notice the different. If there are going to be draughts then these will lose heat faster than little or no insulation.

Bear in mind that you can buy celotex and similar in a wide range of thicknesses and proportionate prices
Also there are outlets selling seconds - usually just damaged corners - at reduced prices.

Bob

 

[Rod]

celotex is not flame resistant unless you buy the R grade.

Rod

 

[timothyedoran]

Actually I got my sums wrong. It would be £200 for new polystyrene and £330 for seconds celotex. Both at 75mm.

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[timothyedoran]

So I think I shall go for the seconds celotex. That way I won't lay in bed thinking about if I should have spent the extra money

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[Mike G]

Never, ever put polystyrene in a building. Celotex every time.

 

[the bear]

Completely agree with you Mike but what's the polystyrene sheets in builders merchants and diy sheds sold for?

Mark

 

[Tusses]

Never, ever put polystyrene in a building. Celotex every time.

Out of interest Mike .. why do they sell it in the sheds then ?

A long time ago I'd have used it, but not any more.

but then , I'd still probably go for rockwool .. just because that's what I got used to.

 

[Mike G]

No idea, I'm afraid. I once 25 years ago put polystyrene under screed in a ground floor build-up, and even there, protected by concrete top and bottom, I still feel guilty about it. Terrible, terrible product.

 

[Rod]

We used polystyrene in bridge building as temporary formwork especially for forming gaps between concrete sections as you could dissolve it out with diesel when the concrete had set.

Rod

 

[timothyedoran]

Next question. Do I need to leave a gap between insulation and breathable membrane on outside, or can it almost touch?

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[Mike G]

In the walls it can touch. The roof is different, depending on what your build up is.

 

[timothyedoran]

In the walls it can touch. The roof is different, depending on what your build up is.

Thanks for the confirmation. I have a good amount of air space in the roof.

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[timothyedoran]

Thanks all for the advice. I have ordered some seconds of celotex. I opted for some boards that vary 70-90mm. Fingers crossed that it's actually in stock.

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