SteamyTea

Did you say the rear of the house was south facing? If so, your proposed design effectively stops the use of PV. If you want to fit UFH, how much can you did down to fit the insulation?

https://www.engineeringtoolbox.com/cooling-heating-equations-d_747.html https://www.engineeringtoolbox.com/air-ducts-sizing-d_1736.html

Double MIRAS stopped in 1989 for new mortgages. Caused a spike in prices over a very short time period. Took years for the housing market to recover. But then we did have the Chancellor setting the interest rates. Regarding local authorities spending. I think each department head should go to every single household and ask for their slice of the cash, i.e. 'I am head of road repairs, can I have £100 please'. Be interesting to see which department collect the most.

I assume you are putting in MVHR. Why not oversize the pipework. Double the diameter and you can quadruple the mass airflow for any give slow speed. You can initially hide the larger pipework behind smaller vents, but why bother. Then, you you need AC, just pipe it in later. Just a case of doing some sums for different climate scenarios i.e. prolonged temperatures above 28°C. The marginal cost of larger pipework should be very small, and you will get a quieter MVHR system when it is on boost.

It is an energy monitor. Similar to the internal display you get with a smart meter. But you can clamp it onto any live wire and read the power used and the energy accumulated. You may need to find a live wire that goes to your ASHP (in the consumer unit maybe) and then can you see what it is using at any time, and what it has used in the previous day, week, 30 days. Quite useful as you can spot things that may have gone wrong. I noticed my usage go up drastically, it was my fridge being permanently on.

Buy this. You can even add a cheap RPi logger to it. https://www.ebay.co.uk/itm/Current-Cost-Real-time-Energy-Monitor-CC128-ENVI/324444722680

My eyesight is often hurt by people swimming in the harbour where I have my coffee. If only the older ones would wear the wetsuits, makes me think of the moon.

Small windturbine and a solar panel. But don't site a small generator next to the inlet.

I saw a stick built extension being built. They nailed a mesh to the external OSB after the Tyvek breather membrane, then rendered it with concrete. Seemed an odd way to do things to me.

I have some ideas that need financing, send me the forms to fill in. I hope @epsilonGreedy does not read this post. He is convinced that all youngsters are going to have to work for nothing just to pay for government borrowings. And live in a carboard box, shoeless, and probably no shirt on their backs.

Just turn the crank, Mousetrap.

Probably not. Heat loss and gain is not linear.

Take a note of the outside temperatures as well. https://en.wikipedia.org/wiki/Heating_degree_day

I wish we just had a poll tax again. I fail to see what the price of an individuals property has. I think we forget what councils are really for, rubbish collecting and put in park benches.

All the 'other stuff' in my house i.e. fridge, cooking, computer, lighting etc, uses about 2 kWh/day.

When I lived in Weymouth, seagulls were a real pest. I was tempted to put super glue by some chips. Would have been noisy for a few hours, but I am sure the rotting carcases would have deterred others. Still find it funny when they take a small child's ice-cream.

My initial thought is the same as @ProDave's. You could try turning the flow temperature up to deliver more power and hope that the rest of the house copes, but you will take a hit on the CoP.

There are usually 2 flow temperature settings. One for the DHW (is that the one you set to 45⁰C) and the one for the space heating. The space heating is usually set lower for underfloor heating systems, but as you are all radiators, 45⁰C seems a reasonable temperature. 8.5 kW seems large for your size place, but that should work to your advantage to keep the CoP higher, which is what you want.

That must be because it is not Ronseal

I would expect 1,500 kWh a year more than you are getting. And 11 kWh in 6 weeks recently points to something wrong. Have you checked it against PV-GIS estimates?

Is 0202 a passcode Just need to find out where to punch it in.

Does weather compensation work best when the ASHP is in constant use? Or does it just use predetermined parameters to try and deliver the designated amount of energy i.e. -5°C outside, Flow Temp 40°C, -2°C outside, Flow Temp 37°C (or whatever)

I am finding all this fascinating. Seems that the biggest problems people have (apart from incorrect sizing), is setting up the flow temperatures. This is probably non-intuitive as a number of things happen in a heat pump at the same time, and it is all a balancing act. Just remember that temperature is not energy delivered. I may have to sleep in this and try and sketch what is happening in the morning (just had my busiest night since October and feeling tired).

is that when you want your heating on? May be useful for charging an EV, just don't do to many miles.

Just before I go off to work, thought I would have a look at your local temperatures. Got some data from Whitchurch, which is fairly close to you I think. Looked at the highest air temperatures on any given day, and the highest dew point temperatures on the same day. Then plotted them. This will give the best case. Time period is 28/12/2020 to 15/01/2021 As the majority of the data points were between 0°C and 4°C, this is about the worse point for an ASHP to be working (there has been a few comments about them freezing up)