Insulating rafters

[cooperphilip]

Hi all.

I am currently in the process of converting my loft into a room for storage. It is strictly just for storage but I would like it to look tidy like a room. I have have had a plumber and electrician in to do there part. I have installed the loft ladders and the flooring. I am now up to insulating the rafters before they get plaster boarded and now need a bit or alot of advice. The rafters are 3 x 2. I want to know the best way of insulating it as they a only shallow, I do not want to start adding more timber to the rafter's to make them deeper as this would loose head height and the roof height is already tight. I need to know are there any insulations out there for my purpose.

Appreciate any advice.

Thanks

 

[SUPERSLASHER]

You can get ceoltex in all sizes from most builders merchants or Wickes diy stores.It is easy to cut to size and will fit well between the rafters.

 

[cooperphilip]

Thanks for reply.

Do I need to leave a gap in the rafters with Ceoltex as I have read with other insulation's ?

I have got a lot of the fiber glass insulation. This will not be suitable for my purpose will it as it will completely fill the whole 3 inches ?

 

[SUPERSLASHER]

No need to leave a gap finish flush with rafter and then screw plasterboard on top.

 

[cooperphilip]

Ok.

Am I right in saying then I can get the 75mm deep insulation to fill the whole depth of the rafter's ?

Do I need to use a vapour barrier then ?

I am going to get silver backed plaster board as a extra insulation. Is this a good option.

Thank you for your advice

 

[noseall]

as you will be effectively creating a 'cold deck' roof then a 50mm air gap should be maintained above the insulation.

 

[noseall]

this is a good guide.

 

[cooperphilip]

Thanks noseall. I have only got 75mm of space in the rafters so that leaves me with 25mm left for insulation if 50mm gap is left. I cant add more timber to rafters to achieve deeper space as the head height is very tight now.

It it essential for this air gap as I have read different ways of doing it.

What is the best way in my situation where I only have 75mm rafter's ?

Thanks

 

[noseall]

50mm insulation and a 25mm airgap.

 

[cooperphilip]

Thanks Noseall.

I have read that you can fill the whole 75mm of the rafters with insulation as long as you do not insulate under neath the big 9 x 2 eaves where the storage is ( The shallow part of the roof).

Is this true or aload of crap ?

 

[noseall]

you could but it may get a bit sweaty below the felt.

type in the words 'cold deck roof' and google more info'.

 

[cooperphilip]

Thanks I will do.


Just a few more questions if you can answer I would greatly appreciate it.

I have got aload of the fiber glass insulation what I have not used. Is that possible to be used in the rafters or is it not effective.

Also do you need a vapour barrier in between the plaster board and the insulation ?

thanks again

 

[noseall]

a vapour barrier will help or use duplex (foil backed) plasterboards.

fibreglass is not really ideal, but would be slightly better than nowt. it is just difficult to deal with the condensation issues.

 

[cooperphilip]

Ok

I think I go with 25 mm air gap and 50mm Celotex.

Would it be better using Celotex then Polythene Vapour Barrier then foil backed plaster board. Or is the foil back plaster board sufficient ?

 

[masona]

Ideally you should have ridge tile vents at the top for air flow circulation