Insulating a loft?

[Kathy]

We're in the process of improving the insulation in our loft. We wish to put insulation at rafter level and plasterboard over this. Now, the internet is contradictory on the best method. A number of the more detailed instructions refer to a "vapour control layer/barrier", such as diagram eleven on this guide. However, nowhere can we find what this "vapour control layer" should be made with, nor can we find anywhere claiming to sell it.

Any advice/hints from people who have already done this?

Ta.

 

[Wowbagger]

Have you applied for a grant? Such things used to exist and when we insulated our first place the Government paid for most of it.

Why do you want to put plasterboard over the insulation? We put loft boards over ours so that we can walk on them.

[GruB]

Friends of ours did that to their house in Gloucester.  It was to ensure the condensation had a chance to dissipate.
We didn't do it to our loft, instead we had all the felt replaced and the roof relaid. 

[alan]

A vapour barrier is essentialy a layer of heavy gauge plastic sheet.

[FatBloke]

Have you applied for a grant? Such things used to exist and when we insulated our first place the Government paid for most of it.

Why do you want to put plasterboard over the insulation? We put loft boards over ours so that we can walk on them.

I think they want to put the insulation in the roof, just under the tiles and then put plasterboard over to give an even finish. They don't want to walk on them.

Celotex is the stuff you need!

[Wowbagger]

Ah ... such things are beyond my experience. We don't even have felt in our roof.

[Woofage]

A vapour barrier is essentialy a layer of heavy gauge plastic sheet.

TPX is the stuff that's used in the trade. You can get rolls of it from builders' merchants. I think I paid about 16 quid last year. Also called vapour barrier.

Make sure the space above the insulation is properly ventilated as otherwise the moisture from the (warm) space below the insulation won't have anywhere to go once condensed out. The Wickes guide states having a ventilated 50mm air gap which was the method we employed when we built the extension to the old Woofage Towers. The reason for this is that traditional roofing felts are impervious so ventilation has to be provided by other means. If you roof has either no felt or a modern breathable felt there is no need to ventilate the space, but you still need one.

[Kathy]

Have you applied for a grant? Such things used to exist and when we insulated our first place the Government paid for most of it.

Need to have a kid or a disability to get a grant in this area.

Coincidentally, if we were to have a kid which were to mysteriously die in a way we were not found to be at fault once we'd benefitted from all the kids' grants (heating, childcare etc), we'd then also make a killing on the life insurance. It's a good thing we're honest, isn't it?

Why do you want to put plasterboard over the insulation? We put loft boards over ours so that we can walk on them.

Fatters guessed it correctly. We already have insulation and floorboards wot we can walk on in the loft. There is also a velux window installed, so it could be a lovely little room. However, there is no insulation at all under the tiles, so the loft gets freezing in winter, and today, with the sun on the black slate tiles, it was about 45 degrees...

Ta for the tips and information everyone.

[Quisling]

Have you applied for a grant? Such things used to exist and when we insulated our first place the Government paid for most of it.

Need to have a kid or a disability to get a grant in this area.

Coincidentally, if we were to have a kid which were to mysteriously die in a way we were not found to be at fault once we'd benefitted from all the kids' grants (heating, childcare etc), we'd then also make a killing on the life insurance. It's a good thing we're honest, isn't it?

Why do you want to put plasterboard over the insulation? We put loft boards over ours so that we can walk on them.

Fatters guessed it correctly. We already have insulation and floorboards wot we can walk on in the loft. There is also a velux window installed, so it could be a lovely little room. However, there is no insulation at all under the tiles, so the loft gets freezing in winter, and today, with the sun on the black slate tiles, it was about 45 degrees...

Ta for the tips and information everyone.

Have you contacted your energy supplier with respect to grants?  Any supplier with more than 50000 customers has to take part in the CERT scheme from April 2008.  They are given a Carbon Emissions Reduction Target which they must meet or face 10% of their turnover sized fines.  Accordingly, all the big 6 suppliers run CERT schemes (which are funded via a hidden levy in every customer's bills).  Under the current scheme only 40% of the CERT actions have to go to "priority" customers.  You won't get free insulation but you should get supported costs.  I'm not on any benefits and I got part of my cavity wall insulation paid for.

The downside is that the savings will be against the full cost of professional installation. If you're doing a DIY job then you'll save more than that in labour most likely.

Good luck.
C

[valkyrie]

It might be easier to use Kingspan panels between the rafters rather than glass wool. I've a vague recollection that you don't need a vapour barrier with Kingspan because it's not vapour permeable anyway.

[Woofage]

Celotex is the stuff you need!

Kathy: I see that the Celotex website now requires one to register for downloads. I have all the spec sheets and I can e-mail them to you if required. Just PM me with an e-mail address.

[alan]

It might be easier to use Kingspan panels between the rafters rather than glass wool.

an excellent suggestion because

you don't need a vapour barrier with Kingspan because it's not vapour permeable anyway.

this is correct

[urban_biker]

I did this in the roofspace of my old house and used glassfibre  block insulation from Wickes. This is like solid blocks of glassfibre which can be cut to size and is just jammed between the rafters with a gap behind it to allow airflow under the roof. you need to be very carefull about this as blocking the airflow can allow condensation to build up and end up rotting the joists.

Once you have covered the whole inside of the roof with this you can then buy plasterboard which has a vapour-proof layer attached. This is in the form of a shiny pastic coating on one side. Then simply screw the pasterboard onto the joists, shiney side upwards, covering your insulation.

You should then tape all the joins between the plasterboard panels to get a full mosistureproof seal

All these items can be bought at your local DIY place, its all fairly standard stuff.

[Kathy]

I did this in the roofspace of my old house and used glassfibre  block insulation from Wickes. This is like solid blocks of glassfibre which can be cut to size and is just jammed between the rafters with a gap behind it to allow airflow under the roof. you need to be very carefull about this as blocking the airflow can allow condensation to build up and end up rotting the joists.

Once you have covered the whole inside of the roof with this you can then buy plasterboard which has a vapour-proof layer attached. This is in the form of a shiny pastic coating on one side. Then simply screw the pasterboard onto the joists, shiney side upwards, covering your insulation.

You should then tape all the joins between the plasterboard panels to get a full mosistureproof seal

All these items can be bought at your local DIY place, its all fairly standard stuff.

This is pretty nearly exactly what our plan was - we are even aware of the existence of  plasterboard with the vapour-proof layer attached. Only problem is, we can't seem to find it in Wickes or B&Q (our two local DIY centres). This was when we began looking for a seperate membrane, and couldn't find that either, hence my original post.

Does the plasterboard with the shiney plastic coating have a special name, and do Wickes stock it but we just can't find it?

Ta.

[urban_biker]

It was a few years ago I did this but I think I bought the plasterboard from an online supplier due to the size of it and had it delivered to my house.

A quick search found this:

http://www.ebuildingsupplies.co.uk/custom/shop/category?categoryID=668

or this which has larger sheets

http://www.buildingsuppliesrus.co.uk/sections.asp?id=5714&aid=&aguid=&b=&guid=

I think its just called foilbacked plasterboard or plasterboard with a vapour membrane.

Remember to buy a size that will fit through your loft hatch.

[Mr Larrington]

When TWFKAML & I did our loft proto-conversion we jammed ordinary fibreglass insulation between the rafters and then held it in place with insulated plasterboard panels for further toastiness.  These consist of a layer of ordinary plasterboard, a layer of aluminium foil and a layer of strawberry blancmange fairly dense insulating foam.  AFAIK, they're not readily available in normal DIY places or builders' merchants, though a decent builders' merchant should be able to order it for you.  If this is the sort of Stuffs you're after, TWFKAML can probably find out the details fairly easily, as this is what she does for a living.

[FatBloke]

This is our loft showing the inter rafter space filled with Xtratherm which comes in sheets of differing thicknesses. Thick for between rafters, and thin for then going over the top. It is already foil covered.



Another pic showing various stages.



The stuff on the floor to the right of the picture is the sheets of insulation.

The room is toasty in winter and cool in summer. 

[Wombat]

Have you applied for a grant? Such things used to exist and when we insulated our first place the Government paid for most of it.

Need to have a kid or a disability to get a grant in this area.

 Comment from an energy efficiency officer (me):
Nope.  We all get it grant aided, by a substantial subsidy under the CERT scheme.  However, this does mean you have to get it professionally installed.  Contact your local Energy Advice Centre on 0800 512012 (don't do it from a mobile, or it won't know where you are from.  Folk over 70 or on certain benefits get it free (its got nothing to do with kids or disability, thats the Warm Front scheme that does that).  Rafter level insulation is tricky, though, and is probably best to do yourself, using the vapour barrier advised.