What to do with gaps in insulation in timber frame ?

[Anonymous]

>:(
A while back a roomful of helpful aecbites recommended building my porch out of timber frame…so I did.it's not finished yet & I've noticed that the “factory fitted” 12cm phenolic insulation has rando
gaps between it and the frame, ranging from 5mm to almost 10mm. My builder doesn't think it's an issue, but I think they're howling cold bridges throughout the structure.
Firstly, putting aside that it's only a porch, who's right about whether it's important or not?
Secondly – assuming I am – what should I do about it? I was planning on filling them myself with no warp expanding foam, but a couple of people reckon it won't go far enough. Ideas & comments very much appreciated!

Thanks,

Tania

[Anonymous]

insulation has random gaps between it and the frame, ranging from 5mm to almost 10mm. My builder doesn't think it's an issue, but I think they're howling cold bridges throughout the structure.
Firstly, putting aside that it's only a porch, who's right about whether it's important or not?
Secondly – assuming I am – what should I do about it? I was planning on filling them myself with no warp expanding foam, but a couple of people reckon it won't go far enough.

You're right; you should fill those gaps. In a way it's good news that they're wide gaps, since that makes it easier to squirt foam in. As to exactly what type of foam to use, I'm afraid I don't know. Hopefully somebody else will!

[Geoff Stow]

I agree with Dave the gaps should be filled especially if the porch is heated in any way. If you have any off cuts of foam it is easy to cut with a fine saw and slithers can be pushed in. I have not heard of any problems using foam filler but it can be difficult to get it in to very narrow gaps. I suggest you contact the insulation manufacturers and speak to their technical dept for advice just in case any of the foam filler reacts with the boards.

[Anonymous]

I don't know how you'll effectively fill 5-10mm gaps. A general note on gaps and cold bridging is that contractors really aren't aware of the implications unless they see it in a form that they can understand. The main carpenter on our house whinged endlessly about Alan Clarke and his pernicketiness on airtightness and uninsulated gaps until he watched an episode of Grand Designs where they built a passivhaus (don't know which one I haven't seen it). He came in the next morning and said he now understood why it was so important. Similarly our engineer ended up introducing several cold bridges which might have been avoided if he'd cared enough about the project to engage constructively with architect and builder.

I guess what I'm saying is that anyone building an airtight structure should get the whole team to watch something that is engaging and informative at the outset. We've been lucky in that our builders are very easy to work with and we have a good relationship but things could have easily gone tits up with a different contractor.

[Anonymous]

Sorry to be a downer but its a timber frame, what did you expect? Its a leaky boat and all you need is enough solar powered bilge pumps then its a zero carbon boat. And like a wooden boat the hull never stops moving and the leaks will continue to spring up randomly. Concentrate on the vapour barrier.

[Mark Siddall]

Gaps in insulation are bad news, to simply because of thermal bridging but also thermal bypass: http://www.aecb.net/PDFs/Impact_of_thermal_bypass.pdf

Mark

[Anonymous]

Thanks all for your comments. I liked the idea of putting the professionals through an education programme; sadly necessary in many instances. Call me dozy, but I hadn't thought of timber frame (and I mean seasoned small timbers, not green oak here) as a leaky moving boat. Not a metaphor I warm to, since I used to live on a number of old wooden leaky boats and know rather more than I'd care to about their maintenance issues.

The comments about a vapour barrier are probably pretty timely. I'm not sure that there is one. I say not sure, because it's not rendered yet and there's a lot of blue fabric on the outside, but nothing on the inside and I presume that's where it should be if there was one…on the inside of the structure before the plaster board?

By coincidence I had an interesting chat with Ecological Building solutions today on the subject of reducing air infiltration in a cold loft; I presume that intello membrane (?) would do the job on the inside of my porch? I'm guessing I'd just line the inside and tape the joints? Would this be overkill for a porch though?

I feel a bit stupid asking all these questions, but then this isn't my area – I just hold the opinion that it's not very many builders' speciality subject either, so I feel I need to work it out myself, even if that means asking stupid questions.

I'm going to start another thread in the appropriate place, but if anyone reads this and has an opinion – do you reckon I should use insulated plasterboard on the outside wall that is now inside the porch (if you follow me)? It occurred to me that it would reduce the heat loss to the porch and as my hallway's always been really cold, that would be a good thing.

Much obliged again for any thoughts and comments,

Tania

PS I've expanding foamed some of the insulation gaps; even using no warp foam it got behind the insulation and pushed it forward – on the bright side, it clearly went right to the back and beyond!

[Author]

Posts