Fri, 10 Jul 2026 15:30:36 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308136#Comment_308136 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308136#Comment_308136 Sun, 06 Apr 2025 18:44:13 +0100 Peter_in_Hungary
For the walls the first thought is
Remove the tile hanging, battens and membrane then fix EPS to the 2x4s and treat as normal EWI (EPS, adhesive with mesh then thin film render to finish)
No breather membrane between the 2x4s and the EPS as the EPS will serve this function (correct ??)
For fixing the EPS to the 2x4s I would plan foam and mechanical fixings.

Would this work?

Would the sides need to be sheathed in OSB first?

If the above won't work what does the team recommend?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308137#Comment_308137 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308137#Comment_308137 Sun, 06 Apr 2025 19:34:10 +0100 owlman https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308138#Comment_308138 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308138#Comment_308138 Sun, 06 Apr 2025 20:23:10 +0100 djh Posted By: owlmanHow about re-thinking the dormer shape and extending the dormer rafters down into the main roof rafters and creating what some call a gable fronted dormer. With just a small vertical element at each end thereby creating a greater under tile area for insulation outside of the original side dormer. walls.That has the advantages of (a) increasing the interior space and (b) reducing the overall insulated surface. Seems like a good idea.

FWIW, I think PiH's proposal will also work. I'm not clear how much insulation there would be in the 'roof' area of the dormer?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308139#Comment_308139 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308139#Comment_308139 Mon, 07 Apr 2025 08:04:33 +0100 GreenPaddy
- sheathing would provide racking/strength to the side panels, which will be lost when you remove the tile battens, so I would OSB them. The OSB could be added internally, if you felt that was a more vapour open buildup.
- I sense there is "some" risk, in that you would be building a timber frame with no ventilated cavity, but it's a relativey small area, albeit exposed at roof level.
- a major part of the role of the VPM on timber frame construction, is to protect it from rain during construction, whilst waiting for the outer skin. If you'll immediately add the EWI, then the VPM will not add anything.
- a lot of the issues with heat loss at dormers is the junction elements (ie, where it butts the rest of the roof). So adding the EWI will tend to cover the main roof rafters, and elements of structure immed around the roof penetration, so that's a bonus (assuming you take the EWI tight to the existing roof, and relocate the flashings out to the EWI face (or close to it).
- insulating the void above the dormer could include some rigid insulation like PIR/PUR at the roof/wall junctions, where you won't get much wool at all, angling the rigid board and foaming in place. Then utilise wool, once you have enough depth to make it effective.
- owlman's suggestion would alter the look of the property (better? worse?) and I guess would need local gov't approval of whatever form in Hungary? You would only gain internal space if you removed adjacent roof rafters, which will have structural implications.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308143#Comment_308143 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308143#Comment_308143 Mon, 07 Apr 2025 11:40:01 +0100 djh Posted By: GreenPaddysheathing would provide racking/strength to the side panels, which will be lost when you remove the tile battens, so I would OSB them.The sides of a dormer are triangles, so I don't think there's any question of racking. Hanging tile battens wouldn't provide any racking strength anyway, I don't think.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308146#Comment_308146 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308146#Comment_308146 Mon, 07 Apr 2025 12:49:07 +0100 owlman I hadn't envisaged doing anything more than simply extending the dormer rafters either side and an obvious continuation of the dormer roof insulation. I assumed that upsetting the internal decor to fit the new gable dormer was a no-no.
The original side faces of the dormer would all stay the same albeit maybe with additional insulation. This would create two forward facing right angled triangles left and right of the old window. For those, re-use old vertical tiles?
Personally I wouldn't bother with local gov, I'd just do it, but that's me.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308154#Comment_308154 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308154#Comment_308154 Mon, 07 Apr 2025 20:39:56 +0100 Peter_in_Hungary
Extending the rafters would be difficult due to the proximity to the adjacent wall. Changing the shape would (theoretically) need planning but for the odd 20 cm I wouldn't bother, but the wall would stop this anyway.

I take the point about putting rigid foamed in insulation over the wall/roof junction.

I would prefer not to have OSB on the side to get a more vapour open construction but my doubt is whether the wall timbers would give enough support for the EPS if it was just foamed and mech. fixed to the timbers or would a backing of OSB be needed?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308157#Comment_308157 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308157#Comment_308157 Tue, 08 Apr 2025 11:13:29 +0100 WillInAberdeen

I have just been through a similar-ish thought process, although not for a roof or with EPS.

I was looking at gluing sheets of insulation onto a timber frame, using beads of foam glue along each timber, and then putting a finish onto the sheet insulation.

I was convinced (by someone I thought was experienced) that the narrow ribbon of adhesive would tear off the face of the insulation. Instead a wide bed of adhesive was needed, eg onto sheathing.

I changed plans and cut the insulation to fit inbetween the timbers, this took ages. This messed up the plan to use the insulation boards for draft stopping (wind washing) and so meant a lot of filling gaps. The timbers turned out not exactly level, so there was more faff adjusting to get the finish to fit onto them, wouldn't have been a problem onto flat insulation.

I now wish I had stuck with plan A. I should have done a test panel to check if the insulation would stick to the timbers without tearing.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308159#Comment_308159 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308159#Comment_308159 Tue, 08 Apr 2025 12:23:12 +0100 djh
Another consideration with the EPS is rigidity. Depending how thick and dense it is, it's rigidity will vary. Will the external render stay stuck to it and either flex with it, or restrain the EPS so it doen't flex, or will the render peel off and leave the EPS flapping?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308161#Comment_308161 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308161#Comment_308161 Tue, 08 Apr 2025 21:09:20 +0100 Nick Parsons https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308163#Comment_308163 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308163#Comment_308163 Wed, 09 Apr 2025 09:30:15 +0100 owlman Another thought; Is render the best finish in an exposed position as this, e.g. maintenance, cleaning etc?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308168#Comment_308168 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308168#Comment_308168 Wed, 09 Apr 2025 18:16:10 +0100 Peter_in_Hungary
I'm not too concerned about splash up or maintenance, the sides have some roof overhang and are a v. small triangle and the front is painted wood - render must be easier than that! The building faces S.W. so gets a good amount of sun so algae growth won't be a problem (the adjacent roof has 18 PV panels that produced 8755 kWh last year).

Hopefully it will be a fit and forget, unlike the existing timber T&G.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308176#Comment_308176 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308176#Comment_308176 Thu, 10 Apr 2025 18:21:44 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308178#Comment_308178 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308178#Comment_308178 Fri, 11 Apr 2025 08:51:58 +0100 Peter_in_Hungary Roof current 0.31 will be 0.16
Windows timber frame with Ug 0.7 stays as existing.

Currently heating with gasifying wood boiler with wood from my own (on farm) sustainably managed forest (overseen by state forestry authority), for the future A2W heat pump fully funded by additional PV.

So the question arises - how much carbon (or/and money) do you invest to reduce the footprint of todays heating or the future heating plan?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308179#Comment_308179 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308179#Comment_308179 Fri, 11 Apr 2025 09:54:49 +0100 owlman
For personal comfort, yes
For upgrading as part of otherwise required general maintenance, yes
For ROI; dependent on your age, quite likely no
For increasing property value, maybe, but unlikely. Buyers usually buy for other reasons and will rip the place apart and "do it up", to their own taste.
For "Saving the planet" doubtful depending on what the total job is but arguably all the embodied energy in the new stuff could be making things worse.

Catch 22..... but, remember Flanders and Swann..."Oh, it all makes work for the working man to do..."]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308180#Comment_308180 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18281&Focus=308180#Comment_308180 Fri, 11 Apr 2025 18:18:08 +0100 Peter_in_Hungary Posted By: owlmanFor upgrading as part of otherwise required general maintenance, yes
This is where I am, re-tiling needed and something has to be put on the dormers so it might as well be insulation as anything else.]]>