JohnMo

Don't hold your breath

HW cylinder £1k to 1.5k incl vat Depending on ASHP £2 to 3.5k incl vat Plus another £500 for misc bits and pipe.

Could just cut and paste the old one, or more shite in shite out normal EPC. They can manually input U values if you have the info to give them. But looks like you ask to see what assumptions they made and reject that one as F...... rubbish.

Mine had all those actuators once, all removed as the system never ran correctly. Big buffer only there because you have lots of zone actuators which act to reduce system volume. Remove actuators - no need for a buffer. I would check the buffer to see how it's controlled it may have its own thermostatic control. So heat pump operates to keep it hot, UFH pulls hot water from buffer. Switching off the UFH may not switch off buffer heating? Your heat pump then goes into a cycle of run for a minute or so switch off, CoP will be 1 or worse consumption of electricity very high.

In the normal sense you are correct. But the lower the house heat losses it moves the target temperature of 15.5 downwards. Our house doesn't need any heat above 10 degrees, so the degree days would start at 10 not 15.5. So if you get the degree days for you location and use 10 as the baseline you won't be be far off.

All you need is an ASHP that does cooling (some don't) and a thermostat that does heating and cooling - Computherm Q20RF for example. BUS doesn't care, if it does cooling. But check for yourself to make sure. But just be careful you are not royally ripped off with the whole bus thing.

Not sure why you need additional relays, think you may be thinking along the wrong lines. Blasting the whole house with high temperature heat is just not efficient, to operate you need thermostats everywhere to control over and under temperature swings. Bit like driving a car with full throttle and idle only. Weather compensation will just supply the house with enough energy to match the energy being lost to the outside world. So the boiler runs for long periods at a low flow temperature. Efficiency gains are in the order of 20 to 30% (less gas usage). Boiler efficiency goes from 80ish to 110%. So only use the boiler manufacturer controller for the main part of house, it will have a time schedule and different temperature profiles, and then TRVs on the bedroom rads. Basically set the WC curve, manufacturer manual will give you a start point on that, add room compensation feature also (setting inside the controller), this will fine tune the settings based on what really happens in the house and may also optimise the start and stop timings. Set the schedule to give you temp you want and setback 2 to 3 degrees only at night. Use the trv's to get the bedroom temps where you want. You really don't need any smart controls, let the boiler control manage it all.

You have too much time on your hands - work harder

Why limit yourself to those boilers. Just get a decent combi, Atag, Intergas Viessmann. If the boiler isn't opentherm equipped as standard move on to another boiler. You need to configure the system as priority demand hot water or X plan. Then have the heating on weather comparison and when cylinder calls for heat the boiler runs at high temperature. The ones I mentioned above do it out the box. You can get a standard kit to convert any opentherm boiler to X plan. https://www.ephcontrols.com/section/pdhw/ Really do you need or just want smart controls? You want good quality trv's with remote sensing, so they measure room temp, not the temperature at the radiator. Tado do not modulate boiler unless you buy the European model, ones sold in UK trade outlets are on off only.

Not sure why you think you need anything special. Our was set to 13 l/s with 16 l/S boost with a recirculating cooker hood. But overall we found we were over ventilating the whole house, so it's now closer to 10 l/s for the whole kitchen diner - No issues a year later and very rarely ever use boost.

Hair dryer and a small roller to press it into the surface.

Is your heat pump control connected to the immersion? What immersion heaters are connected? Buffer and hot water cylinder? Was the noise from the cylinder or buffer? Or general? Was you buffer hot or cold with the heating off?

If they are open loop, they may just be pulling up debris and clogging the exchangers. Or on closed loops and if put in by monkeys never flushed correctly.

Just put solar thermal into to Google and got a 193 million hits and "solar thermal" with 10.7 million hits, doesn't mean I will heat my house with it. In fact just taken my thermal off because it was not as good as expected. And solar thermal is just about obsolete.

There is some nonsense on this site. How many hits you get on Google is no way to make a financial decision. There is the best part of zero maintenance to do on a GSHP, except maintain the anti freeze levels, the only maintenance to do on an ASHP is to clean debris out the condenser. Once either get leaks or refrigerant side failures they are good for the scrap heap - as no one will maintain either.

Pipe length from ASHP is about 8 to 10m to UFH manifold, each way. Cooling from ASHP Flow at 15 degrees on a 20 degree day the EER (CoP for cooling) is about 8. Dropping to 6.5 on a 25 degree day.

All valid points, just do roof integration, sorted.

Does drop a little, and you need more heat anyway - you still get a CoP of about 2.7, for the day you are down to that level. At -2 you are mid 3 and at 7 degrees, 4.5 for CoP. Noise don't really notice as the heat pump is behind the shed.

I would say qualified - what does competent mean with respect electrics and signing things off?

Why a boost switch in the bedroom?

Why? ASHP simple to install zero issues at -10 this year. We have a water bore hole about 45m deep, due to us being on a sand hill, nearly all the drilling money went on steel liners for the bore to stop collapsing. So really depends on on what they find - once you start you can't stop and you just have to pay the bill. If your rock for 10m they could be drilling for weeks

If you have no mixer the flow temp from your boiler or other heat source. If you have a mixer does that have a temperature gauge, otherwise you need to measure the hot temperature at the hot manifold. Moisture reading low - who checked and how did they check? Was it done with floor moisture tester and left for 24 hrs?

Something like that

For a start 100mm just isn't enough with UFH - start at 150mm PIR (0.022). If can't do that would really reconsider the use of UFH.