JohnMo

Run in WC mode everything is always calling for heat. The fan coils just modulate their output to match room conditions by changing fan speed not water flow rate. So all good

Looking at room temperature the line is steady climb, which is good, but suspect your flow temperature is way to high. A 2 Deg rise over 12 hrs is very fast for thick screed. Your +15 degs I would be setting sub 25, maybe 20 to 23, your -5, 28 to 30. Start low, and move up. A hot house is a horrible place to be, especially when it's a thick floor and it doesn't cool for an absolute age. At 10 degs your house will not need or very unlikely to need heating, when dried out. Your running 30 degs, that is nearer what you will need at -5.

Nibe (and others) use an energy integral, so if they are cycling they use a fancy time, to degrees of heat delivered calculation, so they can provide a higher than target temperature, to get a decent run cycle and time off, while still managing the energy delivery to house. Basically ensure short cycling is never an issue and energy delivery is on target.

Your form factor is good, it's a rectangular box. So U value effect is different from a poor form factor (like our house). I would look at a slight bigger scale than just the walls, so floor windows/doors and roof. Get a bigger picture. Note: Passivhaus required U value changes with form factor.

I say look at modulation - can it run all day long at most weathers? As in not cycle?

Our new heat pump has the "App", I did connect to it, you can set time scheduling, set quite mode, turbo mode and holiday, but an utter waste of time when you do WC, so killed the connection.

Very unlikely for it to be any warmer than the room itself. The heat from the pipes will only migrate so far before it runs out of energy

We have our UFH manifold in there, so whole house UFH pipes pass through it. No additional loops needed there, so why put them in?

Who in right mind remodels a kitchen in under 10 years, 20 years isn't that likely. Most kitchen units have a decent long warranty. We have been in our house for 5 years now, redecorating isn't even on the horizon, remodeling a perfectly good kitchen is unlikely ever in my life time. I would possibly build another house first, that's unlikely also. May upgrade a laminate work top but nothing else likely. Your just planning for thing unlikely to occur, adding complexity likely to go wrong.

For me the following comments The floor array hasn't been sized for room output - they have just filled the floor with pipes, so zero design effort. You should really design output to match room design loads just the same as you do with radiators. As it is designed, you may/will need room thermostats to manage overheating, this drives a buffer and other complications. Suspect you will not be able to set room temps by water flow balancing alone. As mentioned dedicated hall loops aren't needed. But may be needed if you need to manage each room temperature via a thermostat. WC and bathroom are next to each other, you could easily share loops. So one loop serving both rooms. To add to this, suspect the utility could also share the same loop. Take into bathroom first, then WC and the utility and then back to manifold. WC will actually need little or no heat as it's internal room surrounded with heat areas. Spiral or up and down makes very little difference as dT (flow return temperature difference) is only 3 or 4 degs, plus floor temp is way below body temperature, so you will not feel it.

Our 4kW can put out around 20L/min of flow if required. It's currently doing around 2kW and the flow rate is around 6-7L/min. So zero need for additional pumps. We are heating 192m² UFH floor area plus a fan coil in another 24m². So do you need the pumps, possibly not, assuming you are flowing the same temperature to each floor area covered by each manifold and don't need mixers. Even then your ASHP should be able to drive an electronic mixer to reduce temp to the lowest flow temp temperature, and do it all without additional pumps/buffers etc. Maybe start a thread, with your details and bottom out what you do and don't need?

Bigger is better, but only if all are the same % oversized, so don't over egg one room and neglect others. Otherwise you end up gagging back one room and still flowing a higher temp at ASHP.

But you would do that to all internals walls anyway, so no different. We have an office the other side of the wall were the UFH manifold is located, timber stud wall - nothing the other side of the wall. Correct

Yep A 21st century essential, just like thermostats were in the 20th and still are to many - that isn't essential and doesn't add value. It's all needless tatt. I do have home assistant, but use it as a simple go to place to see stuff, never found control over the long term reliable. If it stopped working, I wouldn't replace it.

150mm for insulation and any screed above just isn't enough, you should be doing 150mm if PIR insulation at least with UFH, ideally 200mm. Then screed above that, would look at the minimum 50mm.

First time we lit ours, we melted. BUT, treat it low and slow, one log at a time, min air for a clear burn, let it burn almost completely repeat. 3 or 4 logs will heat whole house with ease, without melting you Go through doors not under wall - minimise risk. Ours is flowing through 7 loops, but heat pump has circulation down at 7L/min, can't hear a thing now and when flow is 3x that. No pump though and do you need one - no.

I had some high spots on our concrete slab, used a diamond disc and a hoover attachment/guard attachment on an angle grinder. Used a Henry hoover which survived. Worked well enough, but time consuming. You will still need a face mask.

150mm allowed for insulation and screed? Insulation below and around the structural slab? Where are you in the project - just planning or kart way through build?

Have you thought about a different tariff other than E7? Octopus does one for storage heaters, three cheap periods, one expensive period, and the rest of the time standard tariff. Instead of one long off peak and one very long expensive period. Then just drive immersion via an immersion time switch and allow to top up every cheap period, so you never run out of DHW. You would need a smart meter and time other heater via a time switch also.

That is a bit of trial and error, to see what works for your floor. There is a third option, a slightly elevated WC and thermostat. The ideal is one long run between thermostat trips if you go that route. The 3rd route gives a better overall CoP than a fixed flow temp as your flow temp reduces with warmer weather. Two things to look at, CoP but more importantly is energy input.

That would wake you up. Water mist, you could get back in to bed and finish your nights sleep. If my memory is correct sprinklers cool the flames, water mist essentially smoothers the fire, ok in electric switch rooms etc and delicate environments such as a house.

We have pumped hydro. They want battery banks but the NIMBYs get in the way.

You're as bad as @SteamyTea with your big cut and paste article

If you have solar and not being paid to export, each kWh stuffed into a battery is then worth normal electricity cost, so about 27p. Why would export or grid help, V2H may. Cosy is here for another 10 months anyway.

Plus additional cost and more to go wrong than needed. Did find a system than messed with flow rates rather than on/off valves, but by the time you finished, it add a £1000 just in parts. What benefit is questionable.