JohnMo

WC requires a flow all the time, your flow temp is right to match heat loss with heat input. So you have lowest possible heat input. The heat pump/boiler, just monitors the return temp, adding heat as required. At the moment my boiler fires up for 10mins or so every couple of hours. But the pumps run 24/7 in the heating season.

When I bought my compacfoam, I bought from GBS, was cheapest at the time.

Been there, a couple of time with various bits of our plumbing

The other way with UFH is to batch charge the floor, but you really need a thick floor. I have a 100mm concrete, charged it a 30 degs for about 6 hours over night. At the end of that time the house was at 18.5 deg, an hour later at 19 and stayed there until bedtime. Only disadvantage is you have to fiddle with it, as on really cold days the house started to cool to much over the day as the heat loss didn't match heat input.

One thing that springs to mind is the manifold pump, you can either have a mains outlet with a switch on the wall, think @joe90 does that. I have a thermostat in the hall (which I manually turn up to start pump) and wiring centre, but that is just hang overs from the system I installed. I also have Salus auto balancing actuators on three loops to automatically set a base line, which I have adjusted everything else around.

On my boiler the default was set at 20, I changed mine to 11.

That's about right. You will need the controller for the heat pump, or boiler only.

That's the idea of weather comp, you set the flow temp so you get your house at the temp you want today, as the weather cools, the flow temp increases to keep indoors stable. If it starts getting cooler indoors the curve is to flat, if it gets hotter it's to steep

Your flow temp is too high. That why the house is too warm. You should be able to adjust the curve. Your start temp needs to drop a couple of degrees. You may also need the 35 degree also reducing.

Not sure I would change, even if I had the choice. Steady temperature below the floor, about 8 degs, instead of a breeze at what ever temperature it is outside, could be -5, so heat loss could be bigger.

Ignoring any solar gains, our house sits at a steady 19 degrees. Have a big gas boiler and even bigger buffer, to keep the boiler happy. Flow temp in the floor is 23-26 depending outside temp. 192m2 operating on a single zone.

Almost the same as mine, but I have a further 150mm reinforced concrete below, and strip foundation below that. Due to being at top of a historical sand dune.

If you can get more insulation in the floor with UFH I would, this will help limit downwards heat loss.

This sheet isn't a dpc, it there to stop hydrogen bubbles forming from the reaction between aluminium foil on the insulation and the concrete in the screed.

Very environmental friendly

DHW priority let's the boiler run at two different temperatures, hot for the cylinder heating, warm for weather compensation. I am currently putting 0.5kW into the floor of our house with 36kW boiler. Your demand will never be that low with an older house. Your boiler will turn down to about 10kW, but if you only want to heat part of the house you may need a buffer. This will soak up excess heat, the boiler eventually trip on excess return temp, the heating will continue extracting heat from the buffer, a period of time later the boiler will kick in. You may only need a 25-50l buffer, pipe as a 2-port, you don't need a thermostat on the buffer if you use WC. You don't need a second boiler, that could be a world of pain depending on your gas meter and pipe sizes.

So they come with roughly the same u value, one is cheap, one isn't, your money your choice

Strange I was looking looking at some left over bits and pieces from the build the other day. Both have been exposed to the same weather and fully exposed outside for two years. OSB has has gone grey, other than that looks fine. External Plywood delaminated very badly and very twisted.

Read my post above - thermolite are nearly twice as good as marmox. Plus if your screed thickness is greater than 65mm thick, there is still a thermal bridge below the marmox block as it doesn't overlap on to the insulation.

No you need to compare as built, with as built. If I had done what the architect had suggested, the performance would not of been as good as the final solution, which was also easier and way cheaper to install.

Not correct, from the marmox data sheet. 0.065m/0.078W/mK = 0.8mK/W convert to U value, 1/0.8=1.25 From the other datasheet 0.215/.15 W/mK = 1.43mK/W convert to U value, 1/1.43=0.7 Thermolite is in fact nearly twice as good for reducing the heat loss, even with a worse conductivity. Because they are 215mm high compared to 65mm. It's the size that matters!

Yes. Pump wear when stop and starting, very little wear in steady state running. They do consume energy but a modern pump is in the range 10-30w.

Yes. Setback the local controller will have that built in, as one of the Target temperatures. Not sure if how they do it?

My original plan was marmox, but when I did quite a few calculations comparing to thermolite, I chose thermolite.

Basically set your system to run on weather compensation mode. Your thermostats become limit stops. So set slightly higher temp than you want. You will need to set the WC curve and flow temp. Basically keep turning the flow temp down until most the house is always the temp you want. The thermostats should not be made to control. Rooms that are to warm, decrease the loop flow, room to hot the opposite. Set a nighttime set back of a couple of degrees.