Hello friends, I'm new here. Probably have a few crazy ideas that you've all shot down already but I'll go through them slowly... starting with ideas on floor insulation and underfloor heating.

My building is:

Top floor, 1890s enormous tenement flat in the Southside of Glasgow
Blonde limestone solid walls (around 600-800mm deep)
Lath and plaster inner walls
Drafty but pretty original floorboards throughout
U=1.0 mechanically sealed wooden sliding sash windows throughout (fitted by me a few years ago)
Well insulated roof space - in comparison to no insulation anyway
Fairly enormous rooms and huge headroom - around 3.2m
Ornate cornicing in most rooms which is in pretty good condition.
Standard gas and radiators heating.

I have aspirations to drastically but safely (for the building) reduce our energy consumption. There's some things that I just can't find almost any information on and I hope you lot might be able to give me some guidance. Some things I am planning:

- internal wall insulation (EWI out of the question, at least on the front of the building and real complicated, becasue of neighbours, on the back). Chats on that for another day.
- drastically improving airtightness and implimenting mechanical ventilation. For another day.
- installing wet UFH throughout. Initially fed from gas but future plans for alternative heat sources.

Let's pause at this.

What I am thinking to do for UFH is to build on top of my suspended timber floor. I have a huge amount of headroom and raising the floor 60mm or so would not make much of a noticeable difference. I would have to be careful with my skirting woodwork and door frames but I believe it would be a better option than destroying the floorboards pulling them all up. I've not found much information on WUFH over the top of suspended timber floor, maybe because it's mad, maybe because most buildings don't have so much headroom to play with?

Lay up I'm imagining:

Original Timber floor
Waterproof layer - line of defence from flooding downstairs neighbours if there were ever a disaster/failure.
Woodfibre insulation 30-40mm or so with 18mm UFH pipework inlayed
~18mm layer of screedboard to act as a thermal mass as well as disperse heat
Finishing layer - depending on the room...

Has anyone got any pointers on this? Is it mad?

Things I know:

- It's going to be hard to do
- I need to be very careful about insulating regarding interstisial condensation build up etc.
- It would be easier to move to a building that uses less energy (false arguement if you ask me. This building isn't going anywhere for another 100 years at least and other people would likely use a lot more energy in it).

Thanks for any support or good informaiton :)

I'm renovating an 1840s top-floor apartment and - though it's far from enormous and featured only 1970s architectural features(!) - it sounds there there are similarities in the problems and our objectives.

While I'm using hemp insulation everywhere else, over the existing floorboards I installed up to 280mm of in-situ sprayed closed-cell PU foam, topped by a sand-cement screed incorporating UFCH. This replaced an earlier screed, which went for recycling.

PU was the best option in the circumstances, overcoming problems caused by very undulating floors and irregular room shapes, while adding little additional weight, avoiding interstitial condensation, and adding an airtight & more-or-less waterproof layer.

Posted By: Nick ParsonsI realise the practicalities, but 30-40mm is not much, when you consider that the delta T at the floor will be more than double what it would be if you were heating with rads. Apologies if i am teaching you to suck eggs, but air temp from rads at 20 degrees, and neighbours' flat below empty (at say 10); delta T is 10. UFH flow temp at 40 degrees, flat below 10 degrees - delta T is 30.

Thanks Nick, good point. I hadn't thought about that. So yes, I would need to consider probably quite a bit more insulation below the UFH layer. Hmmmm.

Posted By: Mike1I'm renovating an 1840s top-floor apartment and - though it's far from enormous and featured only 1970s architectural features(!) - it sounds there there are similarities in the problems and our objectives.

Hi Mike, does indeed sound like some strong cross over here. Would be good to hear more about what you're up to. 280mm! That's a a fair bit.. Quite a bit more than I had ever thought. The sand screed idea was something that crossed my mind too. Hope it's going well?

And Hi Gareth - yeah, I'm in with Locohome. We talked about sharing my experience in what I'm trying to do amongst the community here. Hopefully some positives to be shared!

Hi Jake, if you're with Loco Home you probably already know about this, but there's a great video where Lisa Ann Pasquale talks through her retrofit journey on a Glasgow tenement:
https://www.youtube.com/watch?v=Ge3nxP8JCl0

See also the amazing work on Niddrie Road:
https://passivhaustrust.org.uk/news/detail/?nId=1020

Posted By: Warm JakeHaha, sorry for the noob attempt at quoting your messages!

Just go back and edit the post. You don't need to change the text, just click on the Html radio button instead of the Text one under the comment textbox. (just had to do it myself )

Posted By: Peter_in_Hungary

Posted By: Mike1The external walls will have similar insulation ranging from 100mm-ish to 150mm-ish thick, depending on location,

Will this be an excessive amount of insulation with regard to the risks of Interstitial condensation ?

That's one reason for the difference in thickness, and the "-ish" endings.

My understanding - I'm not an expert - is that In fact there are several elements to be considered, including interstitial condensation, moisture penetration from outside, orientation & the ability of the structure to dry during the summer, and properties of the materials, particularly adsorption / desorption.

The Southern 'wall' is actually part slate-clad mansard, part brick/stone with lime plaster, sheltered by a generous roof overhang, so there should be little rain ingress - which seems to be a key factor in avoiding problems (cf. Joseph Little's WUFI studies in Breaking the Mould, paper 5). Due to the structure there's a good amount of air reaching the inner face, and while I'll be stopping that reaching the insulation with a layer of Mento 1000, that will be spaced off the face to allow some air to circulate between the wall and the insulation. The natural insulation will provide good adsorption / desorption of moisture vapour and, on top of that, there's MVHR to help regulate the internal RH, and it's south facing so plenty of opportunity for the warmth of the sun to aid drying in summer. Overall then, the risk seems low and I'm likely most likely to choose 145mm of insulation (100 + 45) for a U-value of around 0.24, but may scale it back to 120mm for U = 0.28. I still have a few weeks to decide.

The other wall is 400mm of rendered brick-stone mix, away from the prevailing winds and driving rain. On the other hand it's north-facing and therefore more problematic, so I'll be going no higher than 100mm of insulation (U = 0.32). I don't want to sacrifice more internal space on this wall anyway.

What I'd really like are the full results from the French 'Réhafutur' experiments (see http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17349), where they used between 30 and 36 cm (not mm!) of various natural materials as internal wall insulation to achieve some ultra-low U-values, with full instrumentation for 3 years. Unfortunately I've not had much time to pursue that since my linked-to post.

https://www.historicenvironment.scot/archives-and-research/publications/publication/?publicationid=651e6f16-087f-408b-ab3d-a59300fd971a
there is some information on the above