How Much Roof Insulation Have you Got?

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How Much Roof Insulation Have you Got?
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Downsizer Forum Index -> Energy Efficiency and Construction/Major Projects

How much roof insulation have you got?

1 inch or less

[ 2 ]

2-3 inches

15%

[ 4 ]

4-5 inches

19%

[ 5 ]

6-7 inches

15%

[ 4 ]

8 + inches

30%

[ 8 ]

I've not got a roof / normal roof!

11%

[ 3 ]

Total Votes : 26

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Jb

Joined: 08 Jun 2005
Posts: 7761
Location: 91� N

Posted: Wed Nov 23, 05 9:50 am Post subject:
Either not enough or too much! I have about 10cm of insulation on the floor of the loft. I also have a combi boiler in the loft which over the last few nights has fired up the central heating on the frost protection leaving the house roasting at 22 degrees while the loft remains at a nice chilly 4 degrees - whats the best way to insulate the roof of the loft? (rather than the floor of the loft)

Alchemist

Joined: 02 Mar 2005
Posts: 123
Location: Aberdeenshire

Posted: Wed Nov 23, 05 11:41 am Post subject:

I insulated my loft by fitting rockwool between the rafters. My rafters are 150mm deep, so I fitted 100mm thick rockwool between them, using garden twine and a staple gun to make a criss-cross web between the rafters to hold them in place. The rockwool lays on the web, leaving 50mm of breathing space against the back of the sarking boards to allow air flow for removal of moisture. It's a pretty quick and dirty method, but works a treat, especially if you keep an eye out for B&Q's half-price deals (sponsored by one of the 'leccy companies).

Jb

Joined: 08 Jun 2005
Posts: 7761
Location: 91� N

Posted: Wed Nov 23, 05 1:09 pm Post subject:

Alchemist wrote:

Is twin adequate to hold that in place? I was thinking of something like that but either stapling laths across the rafters on which 2" of rockwool could sit or doing the same but with a plastic moisture membrame on which the insulation would sit. The latter seems to be recommended but using a lath strikes me as easier (ie I wont have large sheets of membrame to handle while crawling upside down through the attic and won't leave me trying to prevent the insulation all slipping and collecting in one ventilation blocking pile at the base of each rafter)

What do you do for ventilation at the apec of the roof? If I take the insulation all the way up then it will reduce the ventilation, if I run it short then it reduces the insluation

Alchemist

Joined: 02 Mar 2005
Posts: 123
Location: Aberdeenshire

Posted: Wed Nov 23, 05 3:46 pm Post subject:

I started laying (hanging?) the insulation about 2 months ago and it sits in place no problem with just twine. Lath would also work, but I used the twine in preference just because it seemed simpler at the time.I think the trick is to cut the wool slightly too wide for the spaces between the rafters so that there's a little friction.
I have actually backed up the wool with a reflective membrane which is basically two layers of aluminium foil with bubble-wrap sandwiched between. I stapled this to the backs of the rafters and sealed the edges with aluminium foil tape. This is great for banishing any remaining draughts, largely eliminating the thermal break from the rafters, and claims to be a good insulator in its own right. I tend to agree that crawling around with this stuff in the attic is not easy, but ours is floored out, which at least means I can sit down whilst i'm working with it.

Ventilation at the apex in our case is simply due to the gaps between the slates and the steel apex cover. No problem with ventilation there I assure you! I stopped the insulation about 200mm short of the apex on the inside to give a reasonable air channel. I never did check up on the recommendations in the books, which may be wise if your house is a bit newer and better sealed than ours, but I have checked the sarking a few times since and everything seems dry.

If you want I can post some photos. It's a bit of a work in progress due to the number of jobs under way on the place, so you'll be able to see what i'm doing easily enough.

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