JohnMo

It is - it burns really well

The thing to consider also, a well insulated house on weather comp, a 7 to 10 degree day your flow temp are likely to be circa 25 degrees. Your floor temp is likely to be only one or so degrees higher than target room temp. Once rooms are above floor temp the UFH heating is no longer giving heat to the room. The closer the room temp gets to floor temp the lower the floor output. Floor heating is nothing like radiators and takes a bit of a mind set change. So although it sounds odd the floor looks after its self and will start to a small degree moving heat to areas on the north side of the building if you leave the water circulation on.

PIR requires 50% less buildup depth compared to polystyrene. 100mm PIR or 150mm polystyrene. But I would look to maximize the depth of PIR, to get best u value I could. You only get one chance, then it's all buried for ever.

If you are doing cooling get a thermostat that does both heating and cooling. Computherm for example you can select summer or winter modes.

I started our heating journey similar to you, lots of zones, but after 18 months have ended with a single zone. Your buffer size is defined by the smallest zone that can be in use, and the amount of water you need in the available system to give a suitable heat pump run time and allow defrosting. So the smaller the zone and bigger the heat pump, the bigger the buffer. Other thing to consider is flow temperature, to get best CoP it needs to be as low as possible, so coupled with UFH both require long run times, so forme the zones did nothing just got in the way of a simple system.

Set the correct flow temperature and number of hours, as long as our screed is thick enough to store the energy required. Works well with a thick screed not so well a thin screed. Then it's a matter of matching heating time to likely demand due to outside temperature. If you're putting in one Willis, install a spare at the same time, as they are cheap.

Hense putting them below engineered bricks. The engineered bricks take the fixings.

Strip foundation are easy to do, simple blockwork, just need to be careful you design out cold bridges. Single storey big houses are expensive floors to put together there is no getting away from it. Our internal structural walls are sitting on thermolite blocks topped of with 65mm engineered bricks. Simple to install low cost. 200mm of PIR, 100mm concrete screed, perimeter of wall has 70mm PIR upstand.

What are they?

That's hot for an ASHP, you need the flow reducing to about low to mid 30s to get a good CoP. How are operating the system, long or short run times? Is the system all plumped up or is the UFH an additional zone being added to the existing system? There an interesting valve, not seen them before.

Sorry should have been more explicit, that I was just talking the floor, but you also need to take in to account perimeter, area ratio also.

Sorry I may have jumped in without reading all the previous parts of the thread. When working out the heat losses from the floor with ufh you are using the mean flow temperature instead of the room temperature. Just to complicate things. The worse the U value the higher the flow temp has to be, to compensate for the downward losses, etc..

Your delta T will need to much lower than that, 6 to 8 comes to mind. Your floor will be hot and cold spots with a delta that high. Also the floor heat output is calculated by the mean flow temp, the bigger the delta the lower the output for a given flow temp.

If you are thinking a Grant ASHP, go to their website look for an approved installed there. Most Grant installers can do heat pumps, Grant the company hold the MCS certificate.

Still think the equivalent bit,is vague enough to not require MCS installer. That's my interpretation and I will be sticking with it, as many on here have previously done. So will self install, follow guidance within MCS where required and equipment manual where that give specific instructions. Complete a commissioning certificate etc.

I am just adding clarity for the whole of the UK. But the English and Welsh standard you linked to is basically word word identical. Starting as below "equivalent" Development not permitted G.1 Development is not permitted by Class G unless the air source heat pump complies with the MCS Planning Standards or equivalent standards. So it doesn't need to be installed to MCS standards by MCS certified installer. In any part of the Uk

I have just been through the Scottish legislation and basically if it can't be seen and "an ASHP must comply with MCS Planning Standards or equivalent standards", important bit is equivalent. it is permitted development.

Just incorrect, my gas boiler has 3 temperature ranges you can⁶ set and program, all change the flow temp in relation to the heating curve. Plus if you don't have that feature you use your thermostat to have programmed set backs.

Henry are good, Dyson bad, they don't like building dust and it voids the warranty. Been there done it, one broken Dyson. Henry was used when I ground away a huge high spot in my concrete floor, 7 bags of concrete dust later it was still running fine, 18 months later - still running fine.

Our house started with lots of thermostats, slowly over the past year removed them. With a thick screed, and low flow temps they just don't work well, the hysterisis is too large, so temps would overshoot then under shoot. If you have 50mm screed you may be ok.

Zones are areas with a thermostat and or timer. If you run on single zone one thermostat puts the whole UFH off or on, multiple thermostats shuts down or starts up small areas. This will choice affects the need for a buffer or volumiser which will be one of your ticks or otherwise. Best efficiency is from a single zone system run on weather compensation. It also the cheapest to install, as one thermostat and no actuators on the manifold. Can you get a 3 phase 5kW ASHP?

Air 2 water or air 2 air, they are both heat pumps. So no difference with respect planning rules.

More details are you zoning, if how much, one floor more? System volume, flow rate? PV not much to do with ASHP install. Big ASHP that needs 3 phase, are you insulated and draft free, or just a massive house?

It comes out slowly, very slowly. If you are putting a wooden floor on top, you may need a liquid DPC, as moisture levels remained high in ours 18 months after the floor went in.

Trying to fix a REAL problem - not. Buy some bottled water. Or an accumulator. Storage tank means air gapping the supply, a super low pressure system.