JohnMo

Last page bottom left just above the black section where it says 3 A, there is a box saying U window. That is the overall U value of the window, either as plain glass or different window bars options.

Plenty of threads on Willis heater - basically the same as you have linked too but less than half the price.

But you would always loose in court if it did happen. Glass balustrade, safe but you keep the view!

A pretty good rule of thumb. Passivhaus heating specs are designed around around heating via the MVHR system. The 10W per m2 value, specified for the max heating requirement, is the maximum value of heat transfer you can provide to the house when the the MVHR is providing 0.3 ACH. Any more than that the air smells burnt. So if you want to provide 60W per m2, you will need a minimum air flow of 6 x 0.3 or 1.8 ACH, based on your house volume. So 93m2 X 2.4 X 1.8, so 400m3/h. If you want to provide 10kW you are looking at the best part of 800m3/h or around 3.6 ACH. That's a lot of air blowing around.

If you do, really read the spec, especially cooling effect v flow rate.

To many variables really. Buffer no buffer, radiators or UFH, insulation levels, running regime, many zones or one zone, outside air temperature, solar PV and if so how much, what angle it's at, also DHW usage patterns and cylinder size, all have a big impact on running cost.

Get an as designed rating done, then you will have no nasty shocks. And can reassess choices if needed.

Epicair

Sounds a little like you are trying to reinvent the wheel, when nothing wrong with the one we have.

I used ubbink 90mm and all their fittings, no issues

To add to what @ProDave says, the first heat cycle may take quite a bit more energy than subsequent ones, as you need to heat your floor more the first cycle to get it up to temperature. My heating went on on Saturday, I too have had steady 7 degs and pouring rain. Up to 12 degs today!

Your ceiling of the garage should be well insulated, any additional insulation here is money well spent. Having UFH in the garage is plain (sorry to be blunt) daft. You may as well through £2 in the bin each time you walk past it. Any heat added would just heat the ground - not the garage space.

Easy way around that (if you ae concerned) is to have a pipe stat, that breaks the pump supply (normally closed) and if the temp goes to say 50 the stat contacts break to trip the pump

For MVHR to work you need a flow path for supply and extract. Your wet rooms will generate lots of condensation, if you pull air out of the bedrooms that air could be pulled out of the wet room towards the bedroom. That's the main reason you supply dry rooms and extract from wet. Flow rates from MVHR are such that they are rubbish at moving heat from A to B.

Simple answer is they all mix flow and I tried a few before I dumped them all and now don't have a mixer. Flow out of ASHP equals flow to and through manifold.

I would check for a very small leak in the shop WC or under the sink in the lobby first.

Look at specific heat pump cylinders, if it doesn't state the coil size move on. Ideal cylinders are made by Gledhill, but sold considerably cheaper. 3m2 coil Telford heat pump cylinder 3.3m2 coil. Sizing guide for heat pump cylinders

Get a cylinder with a heat pump coil about 3m2. And size the cylinder appropriately. All cylinders are pretty much equal, just capacity difference and coil sizes.

Assuming at least one wall is outside, check the ground level outside - is it at least 150mm below the inside floor level? If not it could be outside ground moisture being pulled in to the house.

I would move away from using small spot lights and use much bigger brighter ones, and way fewer lights. For example our kitchen diner area is like yours, an L shape (we don't have the sitting area you have), but we have 8 lights in total (instead of your 13), the lights are flush fit 150mm dia. The kitchen is very bright with the lights on.

Posi rafter has basically the same thermal losses as the same size wooden beam. The metal webs are about 1mm think, so the cross section is pretty small. I used them in my roof, but then underneath counter battened 100mm and full filled with insulation. To limit any thermal bridges further. Then a vapour barrier and a further 50mm service void. Your first floor, floor build inside the thermal envelope, makes zero difference to heat loss, could be all metal if you wanted.

All really depends on the house and the insulation levels and heating system. If it's very well insulated a thick screed or concrete may be best, a big chunk of concrete to slowly release heat, either drip fed in to floor or added in chunks on cheap rate. No need for zones or complex control, super simple. Retrofit a different story, UFH to free up wall space, not the best insulation, mixed in with a few radiators you may be better with system that takes heat and releases quickly. Horses for courses. No one solution fits all homes.

Things you need from your door. Draft proof, consider a full door set, so frame and door, with double seals. Get a mail box not a letter box. Get as good a u value as you can. But most of all make sure it's draft free. Our door was made a local company , they also made the windows; it's basically looks like a modern door, made with a wooden frame, infilled with insulation and a wooden skin either side - U value is 1.0. Nothing is scratch resistant - if they say it is, they are telling porkies. Treat it well and don't abuse it, it's going to cost you and your wife a fair bit.

Now I am on the computer I can see where you are. Yes we have a strange orb in the sky

That's what I also thought, living between Aberdeen and Inverness, but had under floor cooling on most days when the sun came out, from May to September.