Iceverge

You could consider fiber cement like Hardi board or Eternit cedral.

I blew EPS beads back into the wall where they fell out with a cheap fireplace vacuum from Lidl. Put a mesh material over the vacuum side of the hose. Fill the hose with beads. Swap the hose to the blower outlet and blow into the hole. Repeat. It was slow but it worked.

Cork. We've had highs of about 30 deg and the house didn't get above 26deg. Like you say, smaller windows, especially to the west. It would have been much cooler if my family didn't insist on leaving the windows and doors open while wandering in and out of the garden all day. A single A2A unit is a fraction of the price of a full ASHP and UFH setup. A passive house is like a canal boat. Once it's moving a tiny amount of power can keep it steady state.

I did a payback on cost vs paybacktime. I picked 25 years for all the insulation improvements. I picked this as at the time it coincided nicely with the passivhaus targets, plus a bit for mum. Hence the best spend for us was 200mm eps in the floor, 250mm eps beads in the wall and 450mm cellulose in the attic. Thermally 275mm everywhere might have had the same heating load but the cellulose was cheaper than the eps boards so I put more in the roof. In your case, if you can afford it, get the twinwall with cellulose. It'll be much quieter and more airtight. You might even save money if you don't bother with a central heating system like we did.

There's no rocket science with damp. It just needs to be able to dry faster than it can get wet. In this case you can't prevent it getting wet. An external french drain would be ideal but alas, not possible. You need to let it dry faster that it's getting wet. Heat and ventilate internally, remove any internal paint and or plaster of low vapour permeability. Cement based plaster or emulsion based paints etc. Assuming the floor is also of low vapour permeability the moisture will be all drying via the wall as it has nowhere else to go. If you were to dig out the floor and install an internal perimeter drain to a sump/pump it would relieve much of the moisture pressure from the wall too and it wouldn't be evident above floor level.

I think you're massively over engineering this. 25mm PIR sheets taped at the seams, and foamed to the walls. 2* layers of OSB floating on top, glued and screwed. Leave an expansion gap at the perimeter. Laminate flooring. I can't see a DPM or VCL achieving anything in this case.

Stayed in an airport hotel recently. They had 2 windows. One at the a building external face and another at the room side. Dead silent. It wouldn't be an too expensive an option for domestic houses to put 2x double glazed windows in. It should be thermally magnificent too.

Slates/tiles to match the roof.

Its something to do with smothering @Nickfromwales in a layer of silicone with a spatula.

As I see it you can stop noise by: 1. Blocking airpaths for sound to travel. 2. Decoupling 3. Adding an absorbent layer to stop resonance. 4. Adding mass. There's no secret sauce to sound block plasterboard or mass loaded vinyl. Its just a trade off of mass Vs thickness Vs cost. More standard plasterboard is probably more economical. What U value do you need?

I would consider a shower tray with an upstand too. Should make the floor to wall junction more robust.

Maybe I'm late to the battle here but have you considered if an ASHP is a good idea? They work well at low flow temps and prolonged operation periods and good building fabric. UFH and solid uninsulated floors shouts high flow temperatures and intermittent heating to me. To get the desired output from a heat pump you will have it run it at higher flow temps (bad for COP) for long periods. This means very high electricity bills. Maybe I'm missing something?

Go elsewhere, you'll be lightly to hit screws etc there. Its not too hard. Bang a screwdriver through it and use a bread knife if you don't have any tools. Otherwise a 20mm hole saw would do nicely.

And Solar PV, ASHPs and EV's.

Just put up the cost of gas. People would figure it out themselves.

Looks like it's just behind the plasterboard which is fine Cut a 80 X 20mm hole horizontally near the top of the wall in the plasterboard. If you can't see any cellulose shove your phone in with the video and flashlight on and have a look. JUST DON'T DROP YOUR PHONE!!!!!!!

Do you have any pics of the outside?

There may have been some slimpjg of the cellulose. Can you describe the build up? Is it behind the plasterboard or a membrane too?

There's often debate about this on here but I'm certainly in the camp of avoiding Rigid insulation between studs. Pl Perhaps you could do a wall of each if you're curious and report back.

From the inside out. Skim, 20*70mm battens for service cavity. 50mm PIR on top of the studs. Taped and foamed. 44x95mm studs infilled with mineral wool. OSB sheathing. Breather membrane.

Its the air temperature in the train at 23deg. Everything else will be colder so your bodies conduction and radiation losses will be greater than in summer.

For my 2p worth I was thinking about 50mm PIR Inboard of the studs with mineral wool in between.

If you are concerned about the cellulose how do you propose to check non destructively? Is it worth the effort?

You could jump to 50mm PIR on the wall without services or whatever you can fit. The 400cc studs really have a hit on the performance of the wall at that thickness, the calculator underestimates the true % of timber too. I would foam the boards and tape them with foil tape. Tape them to the windows, doors, floor and ceiling and you'll have a good airtightness layer too.

One of the last two options would be my choice.