Green Building Forum - Thermal break at wall starters?

Green Building Forum - Thermal break at wall starters? Tue, 19 Dec 2023 07:05:47 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174970#Comment_174970 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174970#Comment_174970 Mon, 29 Apr 2013 22:05:22 +0100 Shevek
Any good ideas for doing this in a cost-effective way? Should we just use a normal wall starter kit and then fill gap with PU foam instead of mortar?]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174971#Comment_174971 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174971#Comment_174971 Mon, 29 Apr 2013 23:23:48 +0100 tony Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174977#Comment_174977 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174977#Comment_174977 Tue, 30 Apr 2013 08:27:22 +0100 davidfreeborough
David]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174979#Comment_174979 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174979#Comment_174979 Tue, 30 Apr 2013 08:35:29 +0100 Shevek
There's a perimeter upstand of floor insulation going under the blockwork where it meets the brickwork wall too:
http://www.greenbuildingforum.co.uk/forum114/?PostBackAction=Download&AttachmentID=4027]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174980#Comment_174980 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174980#Comment_174980 Tue, 30 Apr 2013 08:38:14 +0100 Shevek Posted By: davidfreeboroughYou need something with reasonable compressive strength if the wall starters are to work as intended. I've seen Foamglas used in this application.
I think that's further than I want to go at this stage (cost us loads to get out the ground!).

Why the need for compressive strength? What about some mineral wool?]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174989#Comment_174989 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174989#Comment_174989 Tue, 30 Apr 2013 10:53:04 +0100 davidfreeborough
That said, you may not need much compressive strength & EPS100 may be enough.

David]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174997#Comment_174997 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=174997#Comment_174997 Tue, 30 Apr 2013 13:38:51 +0100 tony Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175569#Comment_175569 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175569#Comment_175569 Tue, 07 May 2013 13:01:12 +0100 Shevek Posted By: davidfreeboroughYou need something with reasonable compressive strength if the wall starters are to work as intended. I've seen Foamglas used in this application.

David
Maybe I misunderstand you David but if you look at the literature, which shows the joint being sealed with a compressive sealant, it seems to me there shouldn't be any problem simply filling the gap with mineral wool.
http://www.strongtie.co.uk/pdf/c2k.pdf]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175596#Comment_175596 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175596#Comment_175596 Tue, 07 May 2013 18:23:26 +0100 davidfreeborough
Building the two walls apart means the ties will need to take the entire shear load without the bracing/stiffening provided by the masonry/mortar bed.

Perhaps one of the steel frame ties would be more appropriate? Or could you use TeploTie cavity wall ties bonded to the old wall with resin?

David]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175599#Comment_175599 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175599#Comment_175599 Tue, 07 May 2013 19:34:49 +0100 TimSmall
Given that your neighbour is going to be heating their bit the other side of the boundary, I'd guess that bridge there isn't going to be too serious. In my case I tackled the bridge in a somewhat similar situation by stitching in ~400mm of aircrete "coursing bricks" into the original external wall i.e. just above where it says SVP in your plan. In my case, I was building a new load-bearing engineering brick pillar at this point, so taking a couple extra of the original bricks out at the same time wasn't too much hassle, I only had space for 400mm, but more would have been better.

Model it in Therm?

Tim.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175600#Comment_175600 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175600#Comment_175600 Tue, 07 May 2013 19:36:29 +0100 Shevek Posted By: davidfreeboroughThe literature doesn't seem to have any requirement for compressive strength between the two, but they do require that the new masonry is built tight against the old...
But how can it? The starters themselves are about 8 mm thick.

Edit: I've read a number of instructions for starters now and none of them are clear but I they all assume a vertical mortar joint between the new and old it seems to me, even if there is a flexible sealant as well.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175613#Comment_175613 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=175613#Comment_175613 Wed, 08 May 2013 08:42:12 +0100 davidfreeborough
What concerns me is separating the two by 50-100mm & using the wall tie to carry that shear load unsupported. Normally its buried in masonry/mortar & so cannot twist or bend. If its effectively spanning a cavity then the safe working load may be significantly reduced.

That's what made me think of using a cavity tie instead (but these are not usually rated for shear).

David]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302431#Comment_302431 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302431#Comment_302431 Thu, 13 Jul 2023 14:14:15 +0100 lineweight
This kind of situation comes up quite often: here a new cavity wall is meeting some existing solid brickwork.

I'd like the insulation layer to be continuous, as drawn, but as drawn the inner blockwork leaf is not attached to the brick wall it needs to tie into - other than by my red "what can this be" rectangle.

Some kind of "insulated wall starter" that would do this, would be very useful. As of yet I've not found any off the shelf product that deals with this.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302433#Comment_302433 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302433#Comment_302433 Thu, 13 Jul 2023 14:59:19 +0100 Dominic Cooney
In terms of compressive strength, the screws were done up incredibly tight with no noticeable compression of the PUR. Not sure if in your case the bit of P/board would compress easier?

Please note I am not a Structural Engineer nor an Architect.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302434#Comment_302434 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302434#Comment_302434 Thu, 13 Jul 2023 15:07:40 +0100 lineweight
I suspect that even if what you did would work fine - the structural engineer would not be able to calculate it. If there was an off the shelf product designed for the particular situation then it would be easier to prove it was appropriate.

Perhaps the wall ties between the inner & outer leafs, in conjunction with the fact that the outer leaf can be bonded in to the existing brickwork, can be considered to provide suitable restraint. At some point I will just have to ask.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302435#Comment_302435 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=302435#Comment_302435 Thu, 13 Jul 2023 15:09:46 +0100 lineweight Posted By: davidfreeboroughYou need something with reasonable compressive strength if the wall starters are to work as intended. I've seen Foamglas used in this application.

David

In that case, were there foamglass blocks, toothed in with the bricks/blocks either side, simply as if a few bricks/blocks had been swapped out for foamglas ones?]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304025#Comment_304025 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304025#Comment_304025 Tue, 24 Oct 2023 12:05:49 +0100 wookey I cut in foamglass blocks for our extension, or just cut out some wall so the insulation was continuous, depending on how much structure was needed.
Slot for insulation and wall tie-ins
http://wookware.org/pics/house/extension/html/104-image00225.jpg.html
inner leaf tied in:
http://wookware.org/pics/house/extension/html/113-image00238.jpg.html

New wall tied in here, then slot cut for insulation once one leaf built:
http://wookware.org/pics/house/extension/html/105-image00226.jpg.html

Row of foamglass where extension roof joins wall:
http://wookware.org/pics/house/extension/html/105-image00226.jpg.html

This bit would offend structural engineers - it's rather relying on the wall-ties (it's a cavity wall) to hold everything together - smaller stepped blocks would have been more kosher:
http://wookware.org/pics/house/extension/html/123-image00265.jpg.html
No sign of cracks or movement 10 years later now, so looks like it was OK.

Doorway going in here - roof timbers provide bracing to hold things together.
http://wookware.org/pics/house/extension/html/126-image00268.jpg.html
http://wookware.org/pics/house/extension/html/180-image00335.jpg.html
http://wookware.org/pics/house/extension/html/152-image00307.jpg.html

Nearly all extensions just leave massive thermal bridges at all these locations.
Some more robust ways of doing this for when you haven't got a cavity wall would be good, so the wall can be tied in tension across the thermal break. Something like the schock products for balconies]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304080#Comment_304080 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304080#Comment_304080 Tue, 31 Oct 2023 09:17:39 +0000 lineweight Posted By: wookeyThe big thermal bridge people leave when adding a new wall bugs me. It's very obvious in lineweight's drawing.
I cut in foamglass blocks for our extension, or just cut out some wall so the insulation was continuous, depending on how much structure was needed.
Slot for insulation and wall tie-ins
http://wookware.org/pics/house/extension/html/104-image00225.jpg.html
inner leaf tied in:
http://wookware.org/pics/house/extension/html/113-image00238.jpg.html

New wall tied in here, then slot cut for insulation once one leaf built:
http://wookware.org/pics/house/extension/html/105-image00226.jpg.html

Row of foamglass where extension roof joins wall:
http://wookware.org/pics/house/extension/html/105-image00226.jpg.html

This bit would offend structural engineers - it's rather relying on the wall-ties (it's a cavity wall) to hold everything together - smaller stepped blocks would have been more kosher:
http://wookware.org/pics/house/extension/html/123-image00265.jpg.html
No sign of cracks or movement 10 years later now, so looks like it was OK.

Doorway going in here - roof timbers provide bracing to hold things together.
http://wookware.org/pics/house/extension/html/126-image00268.jpg.html
http://wookware.org/pics/house/extension/html/180-image00335.jpg.html
http://wookware.org/pics/house/extension/html/152-image00307.jpg.html

Nearly all extensions just leave massive thermal bridges at all these locations.
Some more robust ways of doing this for when you haven't got a cavity wall would be good, so the wall can be tied in tension across the thermal break. Something like the schock products for balconies

Thanks, interesting to see these and good to know I'm not entirely alone in worrying about these things.

You are right, in general domestic extensions are built with massive thermal bridges everywhere and people tend to look at you like you're crazy when you suggest these kinds of mitigations.

The other day I was looking at these:

https://www.ancon.co.uk/products/windposts/thermal-windpost-twp2

and wondering if they could be re-purposed in this situation.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304112#Comment_304112 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304112#Comment_304112 Wed, 01 Nov 2023 07:12:44 +0000 tony
We frequently took down the outside skins completely when building extensions adding 15mm or mor space in the new room(s)]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304123#Comment_304123 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304123#Comment_304123 Wed, 01 Nov 2023 13:44:23 +0000 lineweight Posted By: tonyI also worry about the fact that there can be a cavity wall inside the newly extended building with all the possibilities of air ingress, ‘in house winter cooling systems’ thermal bypass on top of the relatively minor thermal bridging at the junction.

We frequently took down the outside skins completely when building extensions adding 15mm or mor space in the new room(s)

You're describing a situation where you extend onto a building that has cavity walls itself, right?

Agreed that in that scenario the outside skin should be removed where it becomes part of the interior - I guess the reason it often isn't is to avoid having to provide structural support for it at higher level.

Assuming it is removed though - it's then fairly easy to tie the new cavity wall to the old one, without any thermal bridges because inner leaf can tie to inner leaf, and outer to outer, at the corners. It's more difficult when the junction is to a solid wall, because whether it's internally or externally insulated, you can't tie in both leaves of the new wall to the existing one without a cold bridge.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304129#Comment_304129 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304129#Comment_304129 Wed, 01 Nov 2023 16:57:41 +0000 djh Posted By: lineweightIt's more difficult when the junction is to a solid wall, because whether it's internally or externally insulated, you can't tie in both leaves of the new wall to the existing one without a cold bridge.Why not build a new solid wall in that situation? Then the insulation can just continue whatever was chosen for the house.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304133#Comment_304133 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304133#Comment_304133 Wed, 01 Nov 2023 18:30:41 +0000 tony
‘Assuming it is removed though - it's then fairly easy to tie the new cavity wall to the old one, without any thermal bridges because inner leaf can tie to inner leaf, and outer to outer, at the corners. It's more difficult when the junction is to a solid wall, because whether it's internally or externally insulated, you can't tie in both leaves of the new wall to the existing one without a cold bridge.‘

I saw a guy cut through the corner and internal walls of a solid wall house and join the internal wall insulation to the new cavity wall insulation seamlessly, he had to strap the cut walls together during the process.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304134#Comment_304134 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304134#Comment_304134 Wed, 01 Nov 2023 18:59:52 +0000 lineweight Posted By: djh

Posted By: lineweightIt's more difficult when the junction is to a solid wall, because whether it's internally or externally insulated, you can't tie in both leaves of the new wall to the existing one without a cold bridge.

Why not build a new solid wall in that situation? Then the insulation can just continue whatever was chosen for the house.

If it's an option to externally insulated both the existing house and extension that would make sense yes. Otherwise I don't think it would.]]> Thermal break at wall starters? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304150#Comment_304150 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10610&Focus=304150#Comment_304150 Fri, 03 Nov 2023 12:09:52 +0000 cjard