Housing - New Build: Insulation question

1 to 21 of 21

- CommentAuthordebbiel
- CommentTimeFeb 28th 2014
I was thinking of using Warmcel insulation in timber frame studwork, with vapour control layer then plasterboard, but architect suggested putting a layer of rigid insulation onto the studwork before the vpl to get rid of the problem of thermal bridging. Is there an ecofriendly rigid insulation I could use for this?

Also, what dimension timber should I be looking at for the studwork if using Warmcel?

Thanks,
Debbie
- CommentAuthortony
- CommentTimeFeb 28th 2014 edited
What u value are yo aiming at? I would put any sheet insulation on the outside and a good vapour membrane on the inside. Your architect is good to want to reduce thermal bridging.

All insulation is eco friendly if you are meaning organic then you need to be careful as organic can rot and decay. All loose fill insulations can slump leaving very awful thermal bridges.
- CommentAuthorfostertom
- CommentTimeFeb 28th 2014
Posted By: tonyAll loose fill insulations Dan slump leaving very awful thermal bridges
Can be readily designed-out.
- CommentAuthortony
- CommentTimeFeb 28th 2014
But isn't always
- CommentAuthordebbiel
- CommentTimeFeb 28th 2014
I'm concerned about the toxicity of some insulations, as well as manufacture, whichis why I was drawn to Warmcel.

So would you put the sheet insulation on the outside of the studwork, then the sheathing board, then the breathable membrane? Is there such a thing as an insulated sheathing board to combine the two?

I don't actually know what U value I'm aiming at - sorry, I'm a real newbie at this! Just want to create a well insulated, healthy home (unfortunately restricted by low budget). Any guidance VERY welcome!
- CommentAuthortony
- CommentTimeFeb 28th 2014
Warmcell is manufactured and can contain toxic substances, indeed warm cell dust is likely to be highly hazardous.
- CommentAuthorjamesingram
- CommentTimeMar 1st 2014 edited
I think most building materials are potentially harmful . Some more than others. Check out greenspec for an over view. http://www.greenspec.co.uk/insulation-introduction.php
- CommentAuthorNick Parsons
- CommentTimeMar 1st 2014
''So would you put the sheet insulation on the outside of the studwork, then the sheathing board, then the breathable membrane?

Is there such a thing as an insulated sheathing board to combine the two?''

depends whether you need it to perform an anti-racking function. Diffutherm (wood-fibre) is used as outer sheathing on TF, but will not, I think, perform as anti-racking board. Heraklith ('Wood wool') is not as good an insulator, but probably wold (subject to manuf's confirmation) do anti-racking. It's also a really good render carrier beacuse of its coarse texture. (Diffutherm, with a really fine texture, is actually a much better render carrier than you'd think).
- CommentAuthorPaul in Montreal
- CommentTimeMar 1st 2014
You shouldn't put unbreathable insulation on the outside, it should go on the inside. We used foil-faced polyisocynaurate in exactly that manner to break the thermal bridge of the studs and also to do double duty as vapour barrier. All joints were taped and all corners were sealed with acoustic caulk (this is very sticky and never sets). Cellulose insulation has a lot of fire and rot retardants in it so the dust is pretty grim if you breathe it. Once installed, it's OK. Most companies use a mix of ammonium sulphate and ammonium borate.

As for the depth of the studs, 6" should be fine I would think - you can use wider spacing between the studs which also reduces thermal bridges.

Paul in Montreal.
- CommentAuthordavidfreeborough
- CommentTimeMar 3rd 2014 edited
Posted By: debbielSo would you put the sheet insulation on the outside of the studwork, then the sheathing board, then the breathable membrane? Is there such a thing as an insulated sheathing board to combine the two?
Some grades of woodfibre insulation provide some racking strength, but it may be more cost effective to use 9mm OSB as the racking board & cover it with cheapest woodfibre insulation.

http://www.ecologicalbuildingsystems.com/products/gutex-wood-fibre/

http://www.pavatex.co.uk/en/products/wall/isolair/

http://www.steico.com/en/products/wood-fibre-insulation.html

David
- CommentAuthorslidersx200
- CommentTimeMar 4th 2014
I haven't looked into it myself, but styrodur c alleges to be one of the "greener" XPS board insulations as the cells are air filled. I have seen it used externally on timber frames.
- CommentAuthorjwd
- CommentTimeMar 5th 2014
The pavatherm/steico method is good (but not cheap) :
plasterboard
service void
osb (racking and vapour barrier)
studs stuffed with wood fibre insulation
pavatherm boards to provide cold bridging protection

cladding

I like the internal use of osb as it is a lot more resilient than a thin membrane - think what happens when you drill the wall to mount a picture and tear the membrane.

Another good idea is to use Masonite beams as studs as that will avoid cold bridgeing to a degree.

cheers
- CommentAuthorcollonach
- CommentTimeApr 1st 2015
I am interested in following the design of the Model D house as at
http://www.ads.org.uk/sust/case-studies/model-d-house
http://www.modeldhomes.com/introduction/
this uses a double panel wall system [95mmx2] with an air tight membrane on OSB between.
I am wondering how in practice you tie the two panels together without puncturing the air tight membrane?
I wonder what folk think of this design as an approach to high insulation/low heating?
- CommentAuthortony
- CommentTimeApr 2nd 2015
Looks like the roof might blow off to me!

Sounds not so economic to use two sets of studs, twice the labour and 0.15 sounds a bit high to me prefer 0.1

It seems strange to bury the airtight layer in the middle of a wall where it is difficult to access and I can't see what it is, if it is the osb I can see gaps and cracks opening up as it all dries and settles.
- CommentAuthordebbiel
- CommentTimeApr 8th 2015
2 more insulation questions-

If I were to use sheepwool insulation in a 140mm studwork wall with OSB on the outside, would I need to use insulation on the inside to stop thermal bridging? Someone suggested alumaflex - I'm still ideally looking for natural/non toxic ideas.

Any ideas for natural/non toxic for insulation for beam and block floor? (Unfortunately discovered the insulated version too late)

Thanks
- CommentAuthordjh
- CommentTimeApr 8th 2015
Posted By: debbielIf I were to use sheepwool insulation in a 140mm studwork wall with OSB on the outside, would I need to use insulation on the inside to stop thermal bridging?

It depends on whether the bridging is a problem for you. You might find it easier to use a double stud design instead.

Posted By: debbielSomeone suggested alumaflex - I'm still ideally looking for natural/non toxic ideas.

There's been a lot of discussion of multifoil insulation on here. Obviously, it's not natural, but if you're still considering it then investigate the technical specs and commercials (warranty etc) carefully.

Posted By: debbielAny ideas for natural/non toxic for insulation for beam and block floor? (Unfortunately discovered the insulated version too late)

Cork? Wood fibre? Sheeps wool in a cassette? How are you dealing with the thermal bridge at the wall-floor junction?
- CommentAuthortony
- CommentTimeApr 9th 2015
Does rock or glass count as natural or will you accept pumice? Natural need not mean organic there are a lot of inorganic things that are natural and some natural things that are harmful, asbestos is naturally occurring and henbane is toxic.
- CommentAuthorSeret
- CommentTimeApr 9th 2015
Posted By: debbielI'm concerned about the toxicity of some insulations

Don't eat them then!

Seriously though, what risk are you trying to avoid and at what point? During construction? Outgassing during occupation? During a fire? Any risks are likely to be small and manageable.
- CommentAuthortony
- CommentTimeApr 9th 2015
Sheepswool wool is edible to some insects and so has to be treated with something. Also as it is biodegradable there could be problems with it.
- CommentAuthordjh
- CommentTimeApr 9th 2015
Posted By: tonySheepswool wool is edible to some insects and so has to be treated with something.

Moths, specifically, and it usually gets treated with borates as per timber or newspaper etc. On the plus side, it has been used as floor coverings for thousands of years, usually these days called 'carpet'. I have heard that since the use of formaldehyde has been banned in carpet manufacturing there has been an upsurge in moth damage to carpets. I don't know what current thinking on protecting wool carpets is.
- CommentAuthorthe souter
- CommentTimeApr 15th 2015
If you have the budget to consider double stud design, look at Steico wall I studs, which can come pre-insulated and virtually eliminate cold-bridging. I have combined I-studs with sheep's wool, using 25mm wood-wool board as anti-rack/ lime plastering surface (fully breathable build-up) but different application than timber frame...

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