JohnMo

The company that supplied the wooden flooring gave the equipment for a a couple of weeks for free. This is basically what I used https://www.protilertools.co.uk/product/tilemaster-hygrometer-moisture-tester?gad_source=1&gclid=Cj0KCQiA-5a9BhCBARIsACwMkJ5nTcNnFTicgLKmn0qg4DdTmrZHiUQ_JRfIP6ppIcd4grcLx-VEs8kaAlAhEALw_wcB

I would do this, change the blocks marked with X for thermolite

Obvious question why? No, manifold pump will circulate. But why do you need a mixer and pump with ASHP? Just use normal sizing calculations and you need prv and filling loop.

If you have the boiler manufacturer controller they can do weather compensation load compensation and mix of the two sometimes. But loads compensation doesn't work well with UFH. Weather compensation outside temp only control, load compensation uses indoor temperature only. I would put dumb limit stop TRVs on radiators to control bedroom temps. Then do the weather compensation curve to suit UFH. Upstairs will also use heat from downstairs so unlikely the rads upstairs will have much work to do. Run it all UFH and rads on or all off.

Bigger radiators are needed. And dT is about 5 degs.

Only thing to be careful of, if you run on thermostat and not weather compensation your set point for flow temp can get a quite big overshoot. I don't have rads but did run direct from the boiler on simulated WC (resistor to give set outside temp and fixed flow temperature)

The only way to do that is way bigger radiators, big buffer or volumiser. Just keep increasing set point temp until you get the the equilibrium point where the boiler can get heat away and you have a relatively long run time. 2 degs on mine make the difference between short run times and running for hours. TPI control makes the boiler go daft. Not really, long run times have way more impact on gas or electricity consumption than lots of short cycling at a lower than optimal flow temperature. Also 10 degs difference in flow temp, is only a couple of percent reduced gas consumption. Long runs win everyday.

Hope you haven't handed over a bucket load of cash

Just looking at the graph. I would operate a little more dumb and at a higher temp. Do you need heating on at 3.30am? If not leave for as late as possible to give boiler way more work to do flow at 60+. As long as your return temp is below 53/54 deg you are in condensing mode, only marginal gains are made after that. It's going to way more efficient than your current operation. Does your boiler control have its own thermostat? or if you want to, do through Home Assistant for now just use the generic thermostat set the hysteresis to 0.5 or more

Sounds like almost every thermostat that runs TPI control is just rubbish. Maybe better just getting an adjustable hysteresis thermostat and make the hysteresis wide, but not uncomfortably wide to give the boiler something to work against.

Report MCS, that is rubbish. Looks like a monkey did it. The grey cables are exposed to UV, so unless they are specifically designed for that, the insulation will fail.

We decided on twin wall all the way. We really didn't want additional heat the single flue gave, it really became a disadvantage due the possibility of overheating the room. You need to understand room heating needs, so you don't melt. An additional 1kW may be too much. We went stainless steel and it draws the eye less, black would just look huge. Lighting the fire is easy enough.

Flexible pipes should be outside the wall not through it. All external pipes are to be insulated. Wall pipe should be sleeves and insulated.

Assume this will be chlorinated or something, so it's not a smelly pool full of nasties after a couple of days. Will make a good breeding ground for stuff like legionnaires etc...

Trouble with the heat pump it tends to be pretty small, so just heating the cylinder can be a long job - many hours. So not sure it would cope doing the equivalent of another cylinder. So that may be a non-starter. Why not just use a basic heat pump to do everything, use the hot tub thing as a huge buffer for UFH. Then a big plate heat exchanger between the hot tub and UFH. Heat pump gets super long (efficient) run times. It would be cheap enough to install, pretty cheap to run. Would be a system very flexible heat pump size. Example of what available with a short look https://www.ebay.co.uk/itm/196989855620?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=8MWPRtN6SYW&sssrc=4429486&ssuid=8KgwDlAbTJS&var=&widget_ver=artemis&media=COPY

You assume everyone can have a smart meter. Without a smart meter and a MCS install you get about 5p for export, and you can only get E7 or standard tariff, without a smart meter. So just about zero incentive to export. Currently have dishwasher and heat pump tumble dryer on and battery slowly charging. So mine is currently saving 30p per kWh (peak rate cost)

I would do a simple cascade system, with supply ducts to bedrooms only. No need to supply to dining lounge, as air would overflow from bedrooms to stairs and down to kitchen. Extract will be kitchen and bathroom only. Supply rates bed 1 and 2 say 35m³h and bed 3 25m³h. So total supply is 95m³h. If you need more flow up the flow rates slightly. Extract rates Kitchen would extract 50 and bathroom 45m³h. 45m³h of the supplied air would be taken by bathroom, the rest would go down the stairs wash through the living room and out of the kitchen extract. Whole house would be be fully ventilated. Only one easy run duct is needed. Do the ducts in 90mm and run 2 to the kitchen to a 2x90mm x 125mm plenum.

Insurance company doesn't ask you for a copy of you completion certificate. Our house insurance started before we actually had a completion certificate, just declared major work was ongoing and the time scale, they asked for money and I paid it

Would need to read the regs, but I think the ones in the post by @Nickfromwales are exempt from planning rules, as they are basically portable. Just a shaped bucket filled with sand.

How have they done that, unless listed building? What are they - do you have links?

Do you mean secondary return loop on DHW? If not done correctly can deplete the cylinder heat pretty quickly. Pipes in full system need to be well insulated. You need to limit when the system runs, so ideally have on a timer or a trigger of some sort. Ideally have a thermostat at the suction of the pump so it knows when the system is hot, then can cycle the pump on off to limit circulation flow. If you have small bore pipes from a manifold to consumers, it may add little advantages but could be an energy drain. It can limit the water draw off volume before hot out of tap. Good for water conservation We have it but it's just on in the morning now. Evening is showers, so nearly hot by time you have undressed anyway.

Watch any quiz show and 20 to 40 years old contestants have zero clue the difference between centimetres and millimeters. That is all they should learn at school. I'm in my 60's and have only used metric most my life, using imperial on really old stuff only.

Again not correct. You can parge coat (then mix of lime, cement, soft sand, mixed to a cream thickness) applied with a broom (and as in image) or you can do a membrane. We have almost no wet plasterers around us, so that wasn't an option. is is

If you want to chase walls woodcrete isn't your friend, as the woodcrete eats sharp teeth for breakfast, soon blunting them. I did the easy way, service gap with battens and plasterboard (dry lined). Battens are screwed directly in to woodcrete (through thin parge coat) with self drilling screws with a blob of sealant on them as they breakthrough the batten. Only bit I didn't do was the plasterboard or taping/jointing. Big polystyrene blocks are quicker and easier, but require suitable props and support y(they weren't available to us, as we are to far north), to hold it all together while the concrete is poured. Durisol needed a few bits of OSB screwed on at corners. Only thing hired in was adjustable props for the lintel forming. All systems have pluses and minuses, choose what suits you. Various direct experiences of different systems offered, some I wouldn't touch with a barge pole, Durisol I would use again without issue. But would also look at polystyrene based ones as they offer airtight out of the box. But only if all the additional support structure were readily available. Rebar not mentioned, Durisol needs very little, all the webs that @Nickfromwales doesn't like is one of the reasons for this apparently. I have rebar around openings and at a couple of high stress corners and that is about it.

Well that won't make then airtight. Obviously the person doesn't understand airtightness.