JohnMo

Doesn't make the answer correct! Which it isn't. There is an over panelling allowance in the total Watts you can generate, but you still need to stay within the specified amps and volts limits.

That isn't really correct, you have a single string which is a series-parallel array. So in this case voltage 9x a single panel and amps is 2x a single panel. So question, is the amperage within limits of the inverter? Possibly not a concern at this time of year but could be in summer, could be where you may exceed the 26A MTTP limit.

Sounds like you need to step back a little. Plan exactly what you want to achieve, put some realistic numbers to the costs. Write It all down. Get a big note pad use It as brain dump, scribble pad. Put it by your bed and instead of rotating a thought around your head write it down. The process is pretty simple, but gets overwhelming because there are many parts that need to be done in a specific order. Plans are good they keep focus, a snagging list needs to to be added to the plan at every stage so things are out of your head and on paper. I am saying on paper for good reason, it quick and easy, it doesn't crash and doesn't need power or internet. I really found this forum useful at the start and planning stage, but once I started the build I didn't want the noise of a 101 opinions of a forum, I had a plan, a design and stuck to rigidly. It shouldn't be an overwhelming process, steep learning curve - yes. Why two properties? Do you need two, why not just one? Why semi detached, that means you really need to do two properties at the same time? Do you have suitable funding in place?

For me I would Do in recirculated mode and come out at the kickboards below your kitchen units. Then install a dMEV (with automated humidity control) fan in kitchen plus all other wetrooms. Undercut all internal doors and have humidity activated trickle vents on all dry room windows or through their walls. Have a proper ventilation strategy.

No gave up in the end and bypassed it, mine was in a summer house, installed a fan coil instead. Without a screed or biscuit mix to get good around contact with the pipes, UFH is pretty pants from my experience. The other way around it, is to throw huge temperatures at it - but that's not in my comfort zone.

Sounds like the heat is circulating, but not being absorbed very well. So not being transferred to the floor. I had a similar issue with an overlay system in theory should have performed great in practice was pretty similar to what you are seeing. Low dT and very poor output, for a given flow temperature.

Yes, full kitchen, 3 bathrooms, decking patio, solar, heating etc all floor coverings, basically house ready to use and passed final inspection.

No too many variables our plot is 2 acres in Scotland not comparable to London. Our ground work other than foundation, isn't included either. We are on the side of hill had to carve out a road etc. The point of a well designed self build, it isn't anything like a developer house, so price wise not comparable either.

If you do option A you need insulation above the outside wall insulation to join the wall to roof insulation - otherwise it will leak like a seize. But I would just do option B, but add a 50mm service void to the ceiling with a vapour airtight membrane on bottom of rafter and service batten below then normal plasterboard.

Are you sure you don't have an air lock? Do you have a call for heat? Is this from anything external?

There are 2 or 3 port designs. I use one between heating and DHW. They come up.on ebay from time time pretty cheap https://esbe.eu/group/products/diverting-valves/mba130

And a home owners manual

Why not just use a simple diverter. I would look to use a MoMo diverter these use a live signal to move valve between positions and then draw zero Watts once there at either end of the positions. Something like an ESBE MBA. Then upstream of valve have a pipe temp sensor set to switch at 20 degs, anything above 20 is assumed as heating and below is cooling. Use the sensor to switch between the two positions. Use something like this to do the switching - nice simple and cheap plus easy to replace. https://www.toolstation.com/corgi-pcs-dual-pipe-cylinder-thermostat/p68281?store=LJ&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gad_source=1&gad_campaignid=17808658009&gbraid=0AAAAAD-vLcX0JQPMjDufZ6UOJnzMg2icv&gclid=Cj0KCQjw9obIBhCAARIsAGHm1mSOycvA4DBwLfJ2NQYEJQUeyqdHr4w7n_OiVbj7YKg3ZkM4cP9y4ikaAs_kEALw_wcB

Have a good read up on that, then you will change your mind and keep a few grand in your pocket. Its useless in the UK.

Normal wood shrinkage cracks - nothing to worry over.

Means I would double my money - 💰 in the bank. I built during COVID the most expensive time you could build. Very limited people allowed on site one trade at a time. Material in short supply and a sellers market. Really depends if your self builder or just paying a builder or where you sit anywhere in-between to the final bill for the build. As mentioned previously, spec and how you buy has a huge impact on costs, but overall how you source has biggest impact. I sourced everything for our build except the cables and fittings supplied by the electrician, and roof was an agreed fixed cost.

You airtightness after second fix for building control. You also need an as built SAP completed.

Wouldn't the constant temperature controller try to mix flows to get a required temp, so may stay at mid point especially between heat pump compressor running cycles? How does your heat pump change between heat and cool? Is it an external switch and dry contacts or software via the controller?

Don't get too hung up on it, if the are not massive. My Passivhaus certified Roof-Maker ones have a Uw of 1.0. I spent more effort to get a thermal bridge free install, thought that was way more important.

Grand designs this week was a single storey, would guess about 180m² came in at £500k. MBC kit, ASHP, good kitchen etc, but a pretty simple design. All work by others. So about £2700 per m². Ours lots of work done by myself with others where needed, about £1800 per m², but quite a complex design in comparison to the above. All depends on complexity, quality of finish etc. how long is my piece of string really. Less airtight, no MVHR, double glazed not triple grazed and way less glazing would have saved tens of thousands. Different kitchen and bathrooms could have added tens of thousands easily. Not adding 100m2 of elevated (structural) decking to the front of the house and glass balustrade again 10s of thousands could have been saved. Bit like asking how much does a new car cost - it depends on...

You would need all the receipts and make sure it's a new replacement policy. A company I worked for had a shipping container with tools in it, until one weekend the whole lot was emptied. Not a penny came back from the insurance. All sorts of exclusion clauses.

It's just a money printing exercise for insurance companies.

It's a sauna, so a cold only shower outside - job done. Or cold plunge pool?

I have mine in the wall and use coander nozzles to throw the air across the room. Used in 3 bedrooms, lounge and long hallway. Lounge two dots at extreme edge of the image by ceiling. Air comes out following ceiling and drops about 7m later. All heated to room temperature, so you don't feel any air movement.

Walk away that is way too small. I chose 90mm to limit number of runs and keep away from noise issues. Costs depend on quality of stuff installed and layout of house and ease of piping runs. I used coander supply nozzles to reduce duct runs but about 50m+. I found with some upfront planning and quite a bit of getting your head around stuff, quite straightforward in the end to self install.