They had to apply for planning anyway because PD states it has to be used for heating only and they use theirs for cooling too. There was a reason why the installer recommended against a multi-split in their situation but I can’t remember.

Thanks for all the really useful advice everybody, despite doing the last house ourselves and basically stripping everything out to a shell, we’re feeling a bit daunted by all the new-to-us very technical work that we are having to learn and then do! So every little bit of advice builds our confidence that we can do this successfully.

As a result we have decided to do the EWI ourselves, but get a renderer in, we will fit the windows in the EWI as advised.

We’re pretty certain that we’ll go the warm roof option, but we’ll strip a section of the ceiling first, which we need to do anyway, to see what we’re up against, and if necessary take some tiles off.

I have requested a quote for windows from Russell timbertech and a quote for EWI from parex - thanks fostertom for the recommendations.

I’ll post in the products category when it comes to product selection for each job - if the renovation category makes more sense, someone let me know.

Thanks again



Ps. I’m thinking about doing a blog - I’m not aware of any for similar properties, but maybe I just haven’t happened across them. Thoughts?

Russell Timbertech are far from consumer-friendly - completing the specification is arduous, with options largely undocumented from their side; their spreadsheet which has to be signed off before the order is placed has to be carefully checked for errors, iterations taking weeks sometimes; and delivery is often delayed. So it all has to be worthwhile and to me it is, as their prifces (every time I've sought other competive quotes) are one third below anyone else and the quality is definitely adequate, if not superb.

Am I wholly wrong or just being pedantic, as usual, when I say that I thought the phrase 'warm roof' (as used by several in this thread) more correctly referred to insulation OVER the rafters (or, on a flat roof, over the joists), thus keeping the rafters or joists warm and preventing them from acting as thermal bridges? If I am correct, is what the OP is suggesting not correctly referred to as a 'conditioned attic', which is rather different, is it not?

Apologies if I am entirely wrong. That is just one of the pitfalls of being a non-specialist in an unfamiliar field (and possibly of too much reading of the US Green Building Magazine articles and forums, where units are mostly non-metric and almost everything is in American English).

Thank you, Nick. My understanding is that there is a considerable likelihood of any internal membrane being provided as a vapour barrier being penetrated by less uninformed and less-invested building services work during the life of the building. Am I correct in believing that as a result, in order to avoid that interstitial condensation risk which you mention, the insulation must be air- and vapour-tight, such as well-taped and joint-sealed PIR or alternatively, on a hybrid WR pitched roof, must include professionally-installed closed-cell spray foam between the rafters, which can act as a vapour barrier (as long as its inner surface is undisturbed)?

Apologies, @PlHadfield, for not seeing your post till today, and thanks @djh for answering!

You said: '' Am I correct in believing that as a result, in order to avoid that interstitial condensation risk which you mention, the insulation must be air- and vapour-tight, such as well-taped and joint-sealed PIR or alternatively, on a hybrid WR pitched roof, must include professionally-installed closed-cell spray foam between the rafters, which can act as a vapour barrier (as long as its inner surface is undisturbed)?''

Yes to air-and vapour-tightness, but (in my view) no to ''on a hybrid WR pitched roof, must include professionally-installed closed-cell spray foam between the rafters, which can act as a vapour barrier (as long as its inner surface is undisturbed)''.

In a between-rafter installation I cannot see how one could guarantee the air-tightness of the spray-foam layer, interrupted as it would be by timber joists which vary their size and shape with changes in humidity. It seems like the 'cause' would be the enemy of the 'solution'. I think that makes sense, unless I have missed something.

Full-coverage (preferably 'intelligent') VCL for me, and service void as per @djh.

(Also, on the pedantic front, although I have 'shot holes' in your idea of closed-cell foam between rafters as VCL, surely your rider ''(as long as its inner surface is undisturbed)'' would be unnecessary as it's closed-cell and does not rely only on the 'skin' as I understand it.)