JohnMo

If you want MVHR instead of PIV, look into cascade MVHR. Supply is pretty much the same as the PIV - one supply, possible some through (internal) wall vent fans to move air towards the extract points as you require. The only difficulty comes in getting ducts to all wet rooms. But you would be better spending your time getting you your existing system to work more efficiently on an as required basis instead of set speed.

Because the press tell people they are noisy, so they go looking for the noise? Some people try to run them like a gas boiler so they run flat out and make more noise than they could?

If doing that plan for a suitable sized buffer within the heating system and the added inefficient running it brings. I did that initially until I started to get the heating bills. Now run as a single zone no buffer and one thermostat. Works well.

We have ours behind a shed and you have to go to back of the shed to see if it's running. Not silent but not noisy either when running. Some click and clonk when starting.

Not a fan, too slow to heat up and collect down unless you mean just in wet rooms (I know as we have it everywhere). You should not need any in bedrooms, especially if well insulated and bedrooms are upstairs, just electric heater just in case you feel the need. Or an oversized radiator when we talked to builders around us, some didn't even want us on site, unless specifically invited.

That's where we started, until the prices came in, then moved to other ways to build. We bought with planning permission and ended up with a house design better than we would have done. We just tweaked it, to get the interior better suited to us.

Are you trying to get elected or something.

Remember that's only external walls, internal construction if studs can 70mm studs and 12.5mm plasterboard each side and taped. Also if horizontal external cladding and using 25mm battens and chasing in electrical and plumbing elements and plaster skim you could reduce quite a bit. If doing block walls 200mm (2x 4" blocks) plus cavity, plus 25mm vertical external battens, plus cladding and plastering. Even with 150mm cavity your down to 400mm.

Just worked out my front clad walls, 520mm thick in total.

Any reason not to connect to existing hot water system. Why does it matter it's not used very often. Even less reason to spend money on it.

No all EPDM but some.

My two roof lights took approx 30 mins to do by the joiner, to fabricate a rubbish one X2 a couple of hours - bridge free doubt it. Bargain.

Just get the installer to heat weld all joints for the upstand. Upstands - form out of Compacfoam. Zero cold bridge, quick and easy

I would do two small ones that fitted between the existing rafters. Big one loads of heat gain when you don't want, loads of heat loss when you don't want it. Then with the money saved do triple glazed.

Not sure about that. I'm either ticking away in WC mode or batch charging. WC mode you really don't need more thermal storage. Have about 60Te. Batch charging will last just fine between E7 periods, so no added value. Think we have a total of 670m of pipe and 7 loops in around 195m of 100mm concrete with pipe clipped to 200mm of insulation. Works fine and dandy. You can stuff pipes at 100mm centres, but even at that I wouldn't be able to flow any lower temps, because the floor is at 22 to 24 and the heat pump runs at 5dT and requires a dT of between 6 and 8 to restart after a heat cycle. So if I flow at 25 to 26, the heat pump runs once than cannot decrease return temperature enough to get a restart permission. So min practical flow temp is 28-29.

No not true I already flow at my lowest achievable flow temp to sub zero if I run on WC mode. Obviously is rocket science, because your analogy is poor. It more akin to a thick towel always over the radiator and only heating those areas not covered by all the towel. The towel will get warm but you are not wasting energy heating it unnecessarily. What point does heating the underside of my kitchen units serve - none.

No Dodgy areas self leveling screed, to make flat. Two different things that may not be compatible. Would glue floor down to get best heat transfer. Access holes make in the floor covering of your choice

I bought a DeWalt air nailer, takes 90mm nails (same as plaslode). Did all the internal stud walls, battening out the ceilings and all the external cladding (using SS ring grove) and a couple of sheds, no issues. Just used a small cheap compressor, don't bother with a good one as well the dust ect kills them.

No zones yes Everything else is nonsense. I am on 300mm centres, have missed everywhere, where there is something on the floor - cabinet, beds etc. max flow temp has been 32 at -9

PV is two arrays, 3.1kW and 3.6kW. battery is a GivEnergy All in one 13.5kW.

Or just get AC coupled battery. But really need to decide what you want the battery to do and then size.to suit.

Your architect is dim, that's not how you work UFH. Installer is worse he should have corrected him. Long and slow is best for all heating types with a heat pump, especially UFH. So if you have WC mode enabled, you run so the thermostat do nothing much, use them as temperature protection. So I would wind the room thermostat (s) up to say 23, and leave the heating to sort it's self out for 24 hrs. If the whole house is hotter than you want the WC curve needs to be adjusted down. If individual rooms are hotter or colder the UFH loops need to be adjusted, more flow is hotter, less flow is cooler. But the heat geek guy should be advising all this. Then once set the heat pump should manage itself.

Not sure about that, it would push new air in to the room and pull air out of room. Believe that are not the quietist units available, so more likely to get switched off, as annoyance

In cooling it's referred to as EER. But a 20 degree day flow at 7 it's about 5.1 while at 12 it's about 6.7. Quite a big jump.

I started in a similar place, it's easy to go down rabbit holes. But always for a building to be as airtight and well insulated as possible. Building Regs is the minimum standard. Go well above those standards for little no cost Start by reading building regs and get familiar with them. You need to know what they require. Use them to test your architects drawings. Actively review and make comments back to architect, make sure they capture everything you want to see. Passivhaus institute websites world wide. Wealth of simple information available. You may not be doing a passivhaus but you get plenty of clues of what to look out for. Don't try to do stuff that is novel, unless you are actually doing it yourself, do what is normal around you. If that's block and cavity - go that direction, if timber frame go that, don't try to force a learning curve. Read up about building form factor. The further you are away from a simple cube, the more insulation you need etc for a given heat loss. But the basics are always the same Airtightness - can you draw a continuous line line around the airtight barrier, if you can't you have an issue. Insulation - read the above on airtightness, same logic applies. Ventilation is very important, decide early what you want, and have routes for pipes built into the design from the start. Are you likely to want cooling, again design in from the start. You can only generally do airtightness and insulation once, but you can pay bills for the rest of your life. Simple is normally best, if it starts to sound complex, stop and leave it for a few days revisit. (I should have listened to this). Ask yourself what do I want to achieve from this. Be sceptical of advice from unknown people (this forum, Facebook etc). Heating system should be simple, zero complexity - most complex stuff in heating systems is people trying to sell you stuff, I have a plant room full of stuff I didn't need to install (all now removed).