Green Building Forum - Loft insulation...but different

Loft insulation...but different

Katymac — Tue, 06 Feb 2007 18:26:46 +0000

DH & I wants to extend into our loft in the near future (1 or 2 yrs)......But we have about 6 inches in insulation up there

I am insistant that we have more - he doesn't want to put more down for it to be ripped up is 18m time

Can we insulate the roof rather than the floor - or will that have no value??

If we can....how??

Loft insulation...but different

tony — Tue, 06 Feb 2007 18:34:53 +0000

150mm will do in the loft for now then. No further action needed. You may as well wait til you do the loft conversion.

Loft insulation...but different

Katymac — Tue, 06 Feb 2007 18:50:35 +0000

Really - it wouldn't be worth filling the "up" bits - as I assume they will need filling when we do convert?

Loft insulation...but different

tony — Tue, 06 Feb 2007 23:27:19 +0000

I presume that you have 150mm everywhere in your loft? with no gaps?

Loft insulation...but different

Katymac — Wed, 07 Feb 2007 07:49:04 +0000

Not the loft panel/door bit & I glue a piece of foam to that - but it seems to be everywhere....oh & not under the cold water tank (my dad said not too)

Loft insulation...but different

Kit — Wed, 07 Feb 2007 08:28:08 +0000

If the insulation isn't up to the top of the existing floor joists and they are going to be left in-situ when you convert - there is nothing preventing you from topping up the insulation to the level of the joists. Not much point if it has to be taken up again shortly though. 150mm isn't too bad a level of insulation for now.
As for the cold tank, you could insulate the outside of it including the supply pipe of course and then it would be possible to put insulation beneath.
You can insulate the roof - either between existing rafters (leaving a 50mm airgap above the insulation) or on the underside of the rafters using counter battens to board to over the insulation afterwards. My current project has 150mm of Thermafleece in the loft floor and 75mm in the rafter space plus a 50mm airgap above the breathable sarking. This is achieved by counter battening the roof prior to slating so the slates stand off the rafters by 50mm. In your case with an existing roof, you will probably need to counter batten your existing rafters to give you sufficient depth allow for insulation and the airgap, assuming your existing rafters are about 75mm. You can leave out the airgap if your sarking sheet is not breathable. It is also good to insulate across the inner face of the rafters to stop them cold bridging.
Non of this is worth doing if you intend to rip out your loft soon though.
Kit
Kit

Loft insulation...but different

Katymac — Wed, 07 Feb 2007 20:10:08 +0000

Thanks.....I guess I need to wait until I extend

Loft insulation...but different

Anke — Sat, 10 Mar 2007 19:45:11 +0000

Posted By: Kit You can leave out the airgap if your sarking sheet is not breathable. It is also good to insulate across the inner face of the rafters to stop them cold bridging.

Hi Kit,

first post after lurking for ages on the old forum...

I am currently debating insulating my roof between and over the inside of the rafters (75mm deep), but am confused by the above statement..

I thought the 50mm air gap was necessary if the roof felt (is saking the same?) is non-breathing to prevent condensation building up. To my thinking -if the roof felt is breathing than the air gap is not necessay, as moisture can escape through it.. have I got this right? - cause if I don't need the air gap the job would be a lot easier for me ;-). BTW, I intend to use 75mm thick foil coated PU sheets for this job...

Anke

Loft insulation...but different

tony — Sat, 10 Mar 2007 21:49:15 +0000

In the UK you will need the 50mm air gap in all cases. Sad but true.

Loft insulation...but different

biffvernon — Sun, 11 Mar 2007 07:27:59 +0000

Air in the UK is little different from air elsewhere and even here there is no legal requirement for a 50 mm air gap. Don't fall into the common mistake of regarding Building Regulations Guidance as legally binding.

Loft insulation...but different

Guest — Mon, 12 Mar 2007 18:36:56 +0000

So how do you get round Building Control if you don't follow the guidance?

Loft insulation...but different

ken davis — Thu, 15 Mar 2007 16:50:57 +0000

katy, you seem to have a few problems understanding building issues; happy to answer any queries i can by phone ,
ken davis dip.arch,RIBA,dip.build.cons,IHBC,MA,etc (35 years experience): 01424 752311

Loft insulation...but different

Katymac — Thu, 15 Mar 2007 19:40:03 +0000

Ken - Thanks

I have written down your number - do you think you should delete it from your post......in case of mad hairy stalkers??

I will be in touch (is that daytime or evening ......& do you know what you have let yourself in for?)

Loft insulation...but different

Katymac — Thu, 15 Mar 2007 19:54:18 +0000

Posted By: ken daviskaty, you seem to have a few problems understanding building issues

(btw - I don't think I have been doing too badly - relatively speaking)

Loft insulation...but different

biffvernon — Thu, 15 Mar 2007 20:30:34 +0000

Posted By: ken davisken davis dip.arch,RIBA,dip.build.cons,IHBC,MA,etc (35 years experience):

Gosh. Biff (swimming certificate)

Loft insulation...but different

ken davis — Fri, 16 Mar 2007 17:37:21 +0000

10 yards breast stroke, cycling proficiency, and several other building related qualifications.

Loft insulation...but different

marionhaste — Mon, 19 Mar 2007 19:34:32 +0000

We also insulated ours over the rafters and under the tiles, which would solve your problem. We used a high-tech but very thin insulation on the roll - it didn't come cheap (around Â£22/sq m), but the effect was amazing. I can't remember the name of the stuff, but could look it up if needed.