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Thermal bridging at window detail


Nic

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Hi 

timber frame ( triple glazed Norrsken windows ) attached on outside stud work.

 

what sort of thermal bridging detail do I need to have / consider ?  Is what’s shown enough? 
 

 

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A quick check is can you draw a line straight to outside without hitting any insulation. As far as I can see, yes you can, straight through the syuds to outside, so it needs mitigating. I don't know the scale on the plan of the window, but it seems like at very least you could insulate the reveal. Could use PIR and 9.5mm plasterboard or splash out and use Aerogel and Magnesium Oxide  board. It is expensive but for a relatively small area it might be worth the £££ expense /m2.

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53 minutes ago, Iceverge said:

What type of windows are they?

 

Inwards opening or ouward openers?

 

1 hour ago, Redbeard said:

A quick check is can you draw a line straight to outside without hitting any insulation. As far as I can see, yes you can, straight through the syuds to outside, so it needs mitigating. I don't know the scale on the plan of the window, but it seems like at very least you could insulate the reveal. Could use PIR and 9.5mm plasterboard or splash out and use Aerogel and Magnesium Oxide  board. It is expensive but for a relatively small area it might be worth the £££ expense /m2.

Any chance you can draw and show what you mean please 🤗

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14 hours ago, Nic said:

Any chance you can draw and show what you mean please 🤗

 

At this stage sorry, no, as it's a tedious drawn-out (sorry!) process with my level of un-technology. @Iceverge has drawn my answer for me, in any case (Thank you!). For future reference in such situations, take the line which terminates at '3,373'. Angle it R or L and for a good while you still have the 3G window 'interrupting' the potential heat-loss. Then move it a little further till the line intersects one of the pairs of studs on either side, and the only thing between inside and outside (apart from the external sheathing boards and membranes) is those studs. That then shows you where action is needed. Similar diagonal lines on a ground floor/foundation section often highlight similar lack of 'cloaking' to potential thermal bridges.

 

Edit: Interestingly the 0.83W/m2K which @Iceverge's detail shows is probably v close to that of a high-spec 3G window, which is good compared to the 'base case' shown, but not as good as better 'wall' insulation. What are the actual dimensions and could you perhaps get say 40 or 50mm PIR on the reveals (or use v expensive Aerogel as I mentioned)?

Edited by Redbeard
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3 hours ago, Redbeard said:

which is good compared to the 'base case' shown, but not as good as better 'wall' insulation.

 

The best windows with the best install are typically still worse than the worst new build wall by about a factor of 4. 

 

3 hours ago, Redbeard said:

What are the actual dimensions and could you perhaps get say 40 or 50mm PIR on the reveals (or use v expensive Aerogel as I mentioned)?

 

Depends on your window frames. 

 

I would leave say at least 10mm of the frame exposed. Beyond that fit as much insulation as you can.

 

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  • 2 weeks later...

Another Thermal bridging question 🙂 

 

how do you deal with services into the property? Such as electric , water,  broadband and things like an external tap for example… trying to get a better understanding of it all 

thanks 

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Ideally bring them up through the slab in a duct and avoid holes in your walls. 

 

If you can't do this I wouldn't be too concerned about point breaches of the insualtion envelope.  They make little differnce to the thermal performance. The airtightness is more important. 

 

Insert conduit's during the build to allow wires to be pushed through and seal them well, both to the airtight and windtight layer . Don't push individual wires or pipes through as they'll be difficult to replace in future. Use a duct or conduit. Holes drilled in a sheet of OSB or ply are easier to seal well and more robust than holes in a membrane so consider a ply "patch" on the membrane to  seal these consuits to. 

 

The mantra is always ONE HOLE for ONE PIPE/WIRE too. A bunch of wires is impossible to airseal. 

 

Always slope the hole outwards slightly for drainage. 

 

 

Edited by Iceverge
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