JohnMo

Why don't you use ubbink foam duct? Ubbink website states Designed to fit Aerfoam 160 mm & 200 mm, with adaptors available for 150 mm and 180 mm

Maybe watch the news. Everything else is going up, looked earlier in the week, the panels I bought were £76 including vat, today £88, when I bought £67 and the prices dropped the next day.

Sorry no clue to the real answer, but don't sockets have to be a minimum given distance from the floor, so wheel chair users etc can use them? So are you allowed floor sockets?

I have 500W (x2) and 460W (x12), suspect they travel down the same production line, get a test at the end and go in either one of several piles, depending on actual measured output. Production from the panels is good. Seem nice solid ,well made panels. Prices are going up daily, so do don't hang about in procrastination mode

I would and did, stainless mesh screwed up and stuffed in, and the spray foamed it all together. Next get bait traps with this in there https://amzn.eu/d/0fyW3NPc It's a one time eat and their dead.

Heat output is pretty poor on low flow temperatures, you don't really want to be flowing 50+ on the cold day. I would be doing 3 or 4 not 1 or 2. Or better still a proper fan coil that is wall mounted. Design them to provide enough heat at 30 to 35 degs and then run fixed flow temp. Suspect towel radiator output at low temperature will be almost zero, they have almost no surface area. My opinion is if you want to run high flow temperature in a low heat loss house, don't bother with the heat pump, save on capital spend, just go direct electric or storage heater. Use the money saved on heat pump and buy a battery, use octopus storage heater tariff at around 10p per kWh from April. We did UFH, you don't know it's there.

Are you planning on just 1/2 small fan coils and towel rads? Or do you have UFH/radiators as well? The kick space coils, I would look at the spec, as they will most likely have a flow temperature permissive to run the fan, this could be based on a boiler flow temperature and not suitable for a heat pump. Are you doing cooling also, that will make a different answer.

Maybe not - panel may generate something, but not enough to trigger anything to work like your inverter.

Watch your flow temperature, your Vaillant is likely to give long run times, so set to a fixed flow temp, no lower than 16 to 17 degs, otherwise you may get dew point related issues - assume UFH, not direct to fan coils.

If you are getting the bifocal version they are glass / glass. Also watch as I found the datasheet and actual panel size where different, datasheet saying they were bigger (long side) than actually size.

If they are heat only thermostats, and not settable to cooling mode, you need to fudge the system to think there is a call for heat. So you need turn up to a high temperature. If your thermostats can do cooling you need to set to cooling mode. But you controller may fight against you depending on how that interacts. With a Valiant you would be better doing everything through the controller and not the third party thermostats for heat or cooling. There are other threads on here that discussed the same issues

My Cosy rate drops to 10.82p (from 1.33p) per kWh and is fixed until 1 October. And will get paid 12p for export. So that's a win. Not sure the difference in price is worth export from battery though. So will continue with excess PV only.

I would do that extra step, make system balance out the box. 1st image just delete the red loop use the blue and green loops to heat those areas as well. Each loop is only 60-70m long so you have plenty of scope for this. Then in bedroom do whichever is easiest to install. You certainly do not need much heat in a utility room.

Architect did the topo as part of the initial planning. Cost me nothing for the GPS mark out, the ground workers included in the costs they quoted me, GPS is part of the base scope.

My guy (arranged by our ground workers) came with drawings loaded into his computer, tied into GPS, then using another bit, just picked the points of one by one, even told me exactly how much higher the site was to the plan. Marked out the foundations, once foundations were done, came and marked out for the blocks. Spent an hour or so at site in total. Technology working. Check measured it all and couldn't find an issue and foundations are pretty complex, compared to anything else I've seen.

Maybe even the person that empties your bins. Obviously had zero idea how to manage drawing revisions.

That maybe the issue (haha) - technician, not an engineer.

You may need to edit replay 350mm or 150mm?

Run it like a proper contract. Weekly progress meeting and minutes taken with actions and agreements stated in black and white. You discuss work scopes and money. If the workers are not there half the time, ask yourself and the builder why aren't they. You should only have about 10 to 16 weeks work to do, from the scope you described depending on house size.

You just need to keep simple, otherwise you will procrastinate and never get any generation up and running.

Why not use mineral wool then zero cutting?

Check the diagonal dimensions to make sure it's square, you have nice oblong building so should be easy to get right, but ...

Trouble is the ideal angle really changes on a daily basis, even an hourly basis if you wanted to be really fussy. I just have around half my panels at 45 degs and the others vertical. Also have 2 set horizontal and they generate nothing mid winter. Complication added, really depends on export limits if it worth changing angles (and if you actually get paid). We are limited to G98 exports, so even in February we get plenty of clipping in the middle of the day if the battery is already fully charged. So no benefits for me, having the complexity. Simple fit and forget

Only if your flow temperature is stupid high. Long outdoor pipes benefit from lower flow temperature, aim for a max of 35 and you will be fine. Then you will be fine with 25mm insulation.

My heat pump is behind a shed and pipes go underground to the house. No real need to go next to house. But the units mentioned by @DamonHD and similar units would be a super easy swop, no plumbing to do. Concentrate on downstairs rooms and maybe panel heaters in bedrooms or leave the storage heaters in those rooms.