SteamyTea

His PI, or the Architects PI may still be valid, and have you had a word with Building Control? They were helpful when I was down there.

No. The ground will rarely get above 12°C, so even if air temperature is higher, you will still be loosing energy heating the mud. You can save cash or all those expensive 'nice to haves', posh kitchen (with or without island/breakfast bar), over the top bathrooms, expensive staircases, expensive glazing etc. All that can be replaced at a later date when finances are different. Design an airtight, well insulated, box with the internal walls where you want them. Make sure your thermal bridging is kept to an absolute minimum, design in the MVHR at the very beginning, so make sure the build is as airtight as possible (even if you do an interim test), fit UFH pipework, but maybe run it off a simple Willis heater, see what @TerryE and other have done, keep the plumbing and wiring simple, but maybe run ductwork for extra cabling later. Internal doors can start off cheap, then put a posh one in every year. Keep an eye on the professional fees, and make sure you are not in for any surprises i.e. connecting to services, ground conditions, storm drainage, environmental reports/mitigations etc, You can loose £50k on those alone @ToughButterCup was keeping a spreadsheet on these costs. Just keep it all very basic, but allow for easy upgrades later. Research all you can. Then do some more research. Only use a friend if you want to get rid of them, and they are well insured.

If I recall correctly, it is 55 outgoing and 54 on the return. If that is correct, it sounds like the pipes are just floating in a void, or well insulated. I think with the NHBC, you have to give the original builder the opportunity to sort the problem, then you have to argue with the NHBC, and loose your claim. You may find it does not cover heating system anyway.

Steam gets it off.

Those will be the ones that happen every 20 years now.

What I used this morning.

Welcome. As you have a top floor flat, you also have roof losses to contend with. But roll the carpet up and stand it up in a corner. Much of this will be a detection game. I had a holiday home in Turton Street. Wish I had kept it till the Olympics came along. No one thought that Weymouth would host the sailing in 1990.

I would be happy if my plastering was that good. Tried it 3 times, 3 total failures. I hate wet trades.

Welcome. Not sure where to start with explaining this. Heat is not temperature. Heat is the old word for energy. So don't worry, at this point about temperature differences too much. As your whole house is new, there will be a lot of mass that will absorb energy, without changing temperature significantly. There will also be a lot of moisture being evaporated, and this, by the very nature of physics, takes more energy than just heating up liquid water (air pressure and humidity levels make a difference as well). If you can, check that the ASHP is not short cycling. This may be a bit hard to establish from indoors if the circulation pumps are constantly running. As a general rule, energy transmission is most efficient at the median temperature. So if the flow is at 29⁰C, the return at 20⁰C, the slab should be, on average, at 24.5⁰C. This does not translate into the room air being at the same temperature as there are losses through the building fabric. Inside the heat pump there is a heat exchanger that takes the hot side of the heat pump and 'passes' the energy to the colder side, the flow to the slab. Generally, you do not have much control over how hot, or cold, the hot side of the heat pump is, that is a function of the refrigerant gas and the fraction of the Carnot cycle used. But as a general rule, you want the flow and return median temperature to be significantly higher than the highest flow temperature going to your space heating and hot water.

Nothing to do with Zoot's extension.

Yes, isn't that what I said. Yes, that is what bolting is. Are they screws or bolts, or hybrids.

No, it is to do with the shank.

They all do, that is how bolts work. This Screw or Bolt debate has been done before. It is material independent and is all to do with what is being joined together and why. Bolts need washers as well.

Full thread is a screw, partial thread is a bolt.

Yes, and that is why they are used. Over a year, they will still stave energy/money, compared to resistance heating, even when the outside temperatures are so low they fail to 'work'. I don't think there is much difference in running costs compared to gas, assuming both system are working as designed.

Had then down here for weeks.

You can argue, on that basis, that night storage heaters are a viable option. And is electricity really that expensive for a low enthalpy fuel, it is less than gasoline at the pumps, and look at the taxes on that.

Back in the 1980s I lived up country in Aylesbury. One very cold winter I thought my gas heating had gone wrong. House was chilly and the boiler was alight. Turned out it was undersized for those conditions. That is when I found that 10 quid fan heaters are brilliant for warming a place up quickly. (My original one has just packed up after 35 years, but it was my fault, opened a door into it and stopped the airflow)

Wrap some self regulating tracing heating as close as you can to the problem area.

I shall add to that. Is it 50 quid every single week. I just put £40 of fuel in my car today. So now have free motoring for about 400 miles.

Others have done the work. https://www.electromaker.io/blog/article/9-best-raspberry-pi-smart-home-software-options But I like to keep things as simple as possible.

I think the problem is language. it is hard to describe in words how it varies with time. But you know what, there is a second language that we all speak, with varying degrees of understanding. Mathematics, use it.

Yes, as has Jeremy Raspberry Pi's seem popular.

Have you done your own quote. Sit down, work out your thermal losses (you have the data already), then go looking for the parts.