Iceverge

You could fill the holes with some tile compound first. Self levelling is mis named I think. More like localised self smoothing compound. 10mm over 2m won’t make much difference and don’t expect it to come out level unless you use 20mm+. It’s a 1:200 slope. Get it as flat and clean as you can first. Then get all your compound mixed up thoroughly. Mop the floor with water so it’s all soaking wet and get the SLC down in one go. Spiked roller or even a trowel may be useful to get it spread out evenly.

How're you planning on fixing the plasterboard?

You could sub in k118 kooltherm plasterboard and probably shave another few mm if you were really in the mood for setting fire to money.

PIR between timbers. I'm not a fan. I'd you really must go for the thinnest option nothing comes close to insulated metal panels. You can get them in tile effect. https://www.insulatedpanelstore.co.uk/rt45mm 80mm and a 50mm insulated plasterboard and you'd have your U value of 0.16w/m2K done and dusted in less than 145mm all in.

Chatgpt if you ask it the right questions will get something very close. Then get your SE to give it a few tweaks and the stamp of approval.

Have you considered building a garden room for WFH? Airtight with a dMVHR unit and good insulation and you'd be amazed at how comfortable it would be. I suspect so amazed you might do the sensible thing to the current house and put it out of its misery.

Sounds like a JCB renovation is needed. Failing that.... patch up the boiler. We can sometimes wish old things out of existence but they may decades left of annoying us left in them. Tackle the fabric of the building before going anywhere near a heat pump or solar. In this order. 1. Bulk water, fix the gutters, point stonework and render, mend broken roof slates, and importantly make sure the local water table cannot get anywhere near floor level. This may involve digging and some French drains. 2. Install some mechanical ventilation. A couple of dMev fans like the greenwood cv2gip would be ace. 3. Airtightness, stop all drafts. It can be achievable with persistence. 4. Insulation, it needs to be continuous and sufficient. Only then should you go anywhere near your heating system.

It was the cost I was thinking of. Caulk is pretty inert as you say. I assumed they charged on a time and materials basis and concrete blocks are pretty porus a d would need lots of sealing if not wet plastered first.

In a similar vein to heating from the slab up, would cooling from the top down work in a passive class house. A single A2A on a top floor landing for instance ?

Here's one of a few technical videos about denby dale. Well worth the view. I would alter the foundation, thresholds and window detail slightly but it's a great starting point.

Are you not worried about using excessive amounts of the aero barrier caulk? Keep us posted.

@tonyshouse http://tonyshouse.readinguk.org/ Good blog here from tony. Don't know if he's still active or not. Similarly from Green building store there's a series of videos about denby dale passivhaus, great details for a cavity wall house.

EPS beads here. They're fine although I am slightly suspicious of the claimed k value of 0.033. I think 0.035-0.037 world be closer in reality. Over all would recommend.

There's an option with the lightweight blocks on the inner leaf. I'm not sure of prices in the UK but in ireland they're three times the price about, €20 more per m2. If you were to use the below 200mm config you could easily drop from batts of 0.032W/m2K to 0.037 which are much much cheaper. Knauf cavity 032 Batts at 150mm are £22.58/m2 and 036 batts at 200mm are £16.38 . About £6/m2 less. https://www.insulationshop.co/150mm_knauf_dritherm_32_ultimate_cavity_slab.html?srsltid=AfmBOooJlH4JJCo9Jukz208_v9VOXP0dZLtipM00uCQZqYL56HiU5rk3 https://www.insulationshop.co/100mm_dritherm_cavity_slab_37_standard_knauf.html Add in a slight difference for longer stainless steel cavity ties and you're still £20 per m2 better off going for the wider cavity. That could be easily £5k for a house.

Have you done the calculations on it? I suggest you do to get a feeling of how little a difference thermolites make. I wouldn't use them. To cracky and brittle and expensive. There's airtightness and then there's airtightness. Ok might be the best you can do with dot and dab if you're careful but wet plaster is the way forward if you want a really tight house. We got well below passive requirements on ours.