SteamyTea

The installation price difference allows for this in the running costs. For the week or two a year that they underperform from specification (if it is an MCS it should be no more that 4 days a year), supplementary heating is used. You really have a problem with ASHPs don't you.

Or 3 kg, which is a lot less.

Yes, between 2 and 3 litres a day, imagine that as a puddle in your living room. It would dry up faster if it was warmed up nicely and allowed to ventilate out the house. Oh, hang on, Page 1

Yes, you can divide it by between 2 and 3.

I just done a very rough calculation comparing the price to heat water with 6 kWh.day-1. Annual cost on standard rate electricity @16p.kWh-1 is £350, E7 @ 10p.kWh-1 is £216. With 4 kWp installed[1] on standard rate it would be £35 a year and E7 £22 a year. So that would be a saving between £200 and £300. Between, and including March and October, there would be excess energy produced. [1] this assumes the PV charges up the water first, based on a SE or SW facing 4 kWp system in Leicester.

Fitting PV onto your roof will take up to 20% of the energy away, so mitigates some of the fails. This does depend on roof design, location etc.

I think for a self builder, pricing needs to be the sum of the individual components. It is not the same as a volume builder where they have different cost centres, multiple sites competing for resources, different finance models, a better working relationship with suppliers etc. If a self builder aims to build at say £1500/m², and end up spending £1200, or £1800, it makes no difference, the house is built, they don't know the what they spent till the job is done. And a self built house is never really finished anyway.

Is an unexpected problem of setting a price based on area is that it justifies corner cutting by the contractor? I typed this before I read the previous post.

Try this for local weather. https://www.metoffice.gov.uk/research/climate/maps-and-data/historic-station-data

Is the land contaminated?

150mm minimum. Any less, get radiators fitted. No point heating the mud under the house up.

How much insulation has be suggested to go under the UFH slab?

Must have been my conjunctivitis.

Is that exposed wall area. and it is kWh.

It is not just the insulation levels that affect building performance. Weather makes the biggest difference. My weather in West Cornwall is very different from East Kent. The Met Office has good data on this.

I think LISA does acoustics. https://lisafea.com/

Not many places down here that don't get fairly good coverage with 4G. Lizard Peninsular is one, strange as it is the home of wireless transmission. May have been to do with Goonhilly not wanting stray signals.

A decent dedicated wifi router, with a colander behind it. I think BT did a good router that claimed it could do 300m. If there is a decent 4G signal, let they use their own service.

Here is a picture of my CurrentCost monitor. What you cannot see us the little Raspberry Pi Zero in the box it is sitting on. All the RPi does is collect all the data for later analysis in Excel. Very simple and reliable.

Humid air is 'damp' Condensation on a door frame is 'damp' High external humidity is 'damp' So do you want help of not?

There should be, but I think they are so small that we cannot really feel them, so as you say, a perception thing.

Stick it into his catflap.

If you know the airflow, you can work out your losses. With the commrcial ones, they have a number of holes of known size and block of a few as the house gets smaller, or more airthight. I think when @joe90's was done, he had only two holes open (that is the minimum on the kit used), then the fan speed is adjusted to get the pressure difference to 50Pa.

What I have done with the CurrentCost This is the data I collect: Date and Time, Temperature, Power 18/01/2021 00:00:07,19.9,00058 18/01/2021 00:00:18,19.9,00049 18/01/2021 00:00:24,19.9,00045 18/01/2021 00:00:29,19.9,00042 18/01/2021 00:00:35,19.9,00039

You buy that off @pocster, wash it thoroughly, in vinegar and carbolic soap.