JohnMo

Video -

Exactly the same a solar assist heat pump outdoor condenser, but indoors

Once compacted it's just very thin insulation, with same thermal properties as thin insulation - it has zero reflective properties without an air space to reflect into. Would use any other insulation than this. If it's first floor just 25mm EPS or XPS.

What boll0cks. I'm running pure WC. Have run WC, thermostat mode, batch charge mode and hybrids of all three. You could set target flow temp to 35, I've done that also. But ASHP just runs full load with zero modulation and will most likely never get there before the thermostat trips out. You get best CoP at a medium load position, so you want the heat pump to hit the target temp and then take control and modulate down. Any UFH with a thick screed, the floor is the dominant force, its temp dominates return temp, return temp dominates max flow temp achievable. Simple science, not because it works for me. Many on here run a thermostat based system, its just a matter of setting the lowest flow temp you can get away with not the maximum.

Because your system and house should run at that min outside temp. So run will be proportional to outside temp. Cold day run all the time, 10 degs for a couple of hours. Lowest temp to do that and get best CoP

The other acceptable running mode is pure thermostat, set a fixed flow temperature of 28, still run as a single zone. Your thick screed will demand very long times and at that temp CoP will be great.

The assumption is incorrect though. Open window you let cold air in hot out, but the thermal capacity of air is very low, building fabric the thermal capacity is very high. You close the window, the air within the building is reheated by the now warmer fabric (especially the floor) pretty quickly. You floor will not lose heat for many hours/days even with heat source off.

Some simple science Your floor even on a dull day will not be much hotter than the room, maybe 1 to 3 degs at the surface depending on outside temperature. Let's assume room is 20 degrees, floor surface 23, sun comes out room increases to 23. Now as floor is 23 and room also 23 the floor no longer transfers heat to room. Sun goes away room temp drops, floor starts giving heat to room. With a thick screed (think you have this) the floor just acts as a huge buffer for energy. Thick screed doesn't act like a radiator due to its thermal capacity, think more a swimming pool, once up to heat it isn't cooling quickly. Once you allow to cool it takes an age to heat up. Setting up WC is pretty easy for UFH, start with a gradient of 0.5. so every degree outside temperature drops you increase the flow temp 0.5 degs. Start with a flow temp of around 20 or 22 at 10 degs and 28 to 30 at -5. Ideally let it run for 24 to 48 hrs. Adjust curve up down to suit. Small changes have a big change. System doesn't need to know internal temperature. You set the curve to balance heat loss and heat input. You better starting cool rather than hot. WC is completely open loop.

That's what they have now!!!! 🙄😉 No, it's run on WC, not fixed flow temp, so fixed flow temperature would be completely different, may need a buffer if you are messing flow with TRV etc.

So you are saying to run everything at a fixed temperature, with TRV's on rads and how are you managing UFH room temps, thermostats?

Sounds like loads of PV, battery and generator is required - if you an get mains gas run the generator from that, exhaust heat exchanger, to do the heating while generator is on. And some batteries.

That's a good spot - even Cool Energy say it's a mid point valve

Then don't ask questions you don't want a truthful answer too - which isn't what you want hear!🫣

Email them back and state what you did, they will update the U values etc. Then if you get a fail, get ready to install solar PV to make up the difference.

You have a Vaillant heat pump, I would just install an ESBE electronic mixer (VRG valve and actuator) at the UFH manifold (you won't need an additional pump). Set the controller to do 2x zones, each with its own WC curve. The zone for the UFH, the Vaillant controller will control the ESBE mixer as needed to follow your defined curve. What will happen is if the radiators call for heat heat pump runs at higher temp and controls mixer to UFH. If radiators aren't calling for heat the heat pump will reduce flow temp to satisfy UFH demand only mixer will be fully opened. I wouldn't add any zone valves, leave the radiator alway open and when they don't need additional heat they run just like they are now and it keeps the water volume engaged and full circulation path for flow rate. IVOR mixers are great, but you then need to run the UFH off thermostats, as it will receive a fixed flow temp and you always need operate the heat pump at radiator temps.