Barn conversion - best way to insulate roof.......?

[John Rumm]

Even with a cold deck roof, you can do away with the vents if you use a breathable felt.

[Christian McArdle]

It isn't just the ridge line that matters. It will still require planning permission if you increase the volume at all, so you might as well apply and do it properly with 100mm all the way. Also, the highest point of the roof is where most of the heat would be lost. Leaving that part uninsulated would be disproportionately bad for the thermal performance.

Do you have a target u-Value yet? 100mm entirely above would give you a u-Value of 0.20 (figure 6a method).

Christian.

[Simon Hawthorne]

I don't Christian...

My previous plan was to have renotherm do what they do - and not worry about insulation. I've battled with the planners for a year now and do not intend to go back to them for anything - so I don't want to change the roof volume/height. As I've now opted for local roofer to come in, remove tiles & lathes, get rid of tons of old 'torching' (which has all pretty much much fallen off and is on the upper floor), and then reubuild using breathable membrane and original tiles.

Seriously considering having spray insulation when the job is complete as there is an awful lot of work involved in everything suggested here so far - and I don't have the time or expertise to do any of it!

Why isn't anything ever as easy as it looks!

Cheers

Simon

[Pete C]

Hi,

Why not insulate to rafter depth, plasterboard on top, then lengths of wood and plaster to simulate roof beams and 'ye olde' plaster ceiling?

98% of the population won't know better, the other 2% will look at the other beams and know the roof is relatively recent anyway.

cheers, Pete.

[Mike]

Are you sure on this ? Unless it is in line with another building I can't see it being an issue. You aren't increasing the internal volume after all.

I was assuming you'd still have the 50mm you suggested between the rafters as well. Agree without it all the heat would shoot out the top.

[Christian McArdle]

Avoid spray on like the plague. Not only does it prevent future roof maintenance, but it has a lower insulation value than Celotex. You would probably need well over 100mm of it, which will totally bury the rafters anyway.

If you don't want to raise the roofline, then you will have to bury the rafters. End of story, I'm afraid.

You are planning to submit a building notice aren't you? Because the BCO WILL require you to install a goodly amount of insulation, probably at least

100mm of celotex/kingspan or 200-300mm of anything else.

Christian.

[Christian McArdle]

External volume is the deciding factor for planning permission.

You would have to do some serious calculations to show that the performance of the whole roof (or if preferred, the whole building) meets the regulations as a whole. It is permitted to use less than the recommended insulation in one part, if the lost energy efficiency is regained elsewhere on the property.

Christian.

[Doctor Evil]

That is poor advise. It is just foam. Foam sprayed on.

it doesn't. It can be cut away.

It makes up for that by making the roof air-tight.

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[Yekal]

[Doctor Evil]

There is no independent evidence that this Tiso Super actually works. It is like bubble wrap. There is some insulation value in bubble wrap and the stuff does make the roof airtight, not much else though.

I didn't mean to rain on your parade but it really doesn't work, so I wouldn't like others to do the same as you.

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[Mike]

Hang on. Wasn't it you in your IMM guise who pointed to some web-site in the US showing these products did work the last time we had this discussion ?

[Doctor Evil]

When cooling is required. They have an effect in Florida and that is what the web site stated. In more northerly states the effect was minimal to not worth considering.

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