Tue, 01 Sep 2026 23:37:36 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311292#Comment_311292 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311292#Comment_311292 Sun, 30 Aug 2026 09:27:39 +0100 Victorianeco
Still undecided if I'm going to adopt the fabric first approach (focussing on CWI beads and then EWI with windows in the insulation layer)

or

More later research focussing on reducing embodied energy at source and just use CWI beads and then silicone render over existing.

Just wondering if anyone could share the optimal window fitting detail for each approach and how I could mitigate thermal bridging particularly if I adopt the latter approach?


Property is currently ~20mm render on external reveals and PB and skim internally on the reveals but solid render/skim on the internal walls.

Windows will likely be alu-clad 3G from Allan Brothers, property will be having ASHP and solar.

I know I've harped on about which approach to take but this decision of CWI v CWI with EWI is holding up the project and causing conflict with her indoors.

Property in question linked below for context:
https://drive.google.com/file/d/12ZZsoLmjjSMoA4AW8HBQ_oQzmi9waWuE/view?usp=drivesdk]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311301#Comment_311301 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311301#Comment_311301 Tue, 01 Sep 2026 18:42:55 +0100 Victorianeco
Thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311302#Comment_311302 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18472&Focus=311302#Comment_311302 Tue, 01 Sep 2026 22:26:35 +0100 fostertom
CWI is cheap and easy, as it goes - small embodied carbon I'd a thought. So might think to do that, then thinner EWI to top U-value up to what you want it to be. But if EWI is thinner, can't mount windows in the EWI zone.

I'd say the lo-embodied route would be a 3rd option - CWI alone, which only makes sense if doing the consequent extra heating by increasingly decarbonised electric heat pump incl, for best COP, likely greater or lesser re-engineering of any extg rad system (ideally UFH).

If sticking with gas and extg rad system, then the old approach, concentrating on in-use carbon-fuel saving, is a must. In that case, thick EWI only, simplifying window location.]]>