SteamyTea

Welcome. It will be good to have someone that has experience in ICF. A few people on here have used it, but they tend to be one offs, so the next person that uses it seems to me, to be just reinventing the wheel.

My guestimate was pretty close. Insulation, generally, needs to be within the airtight envelope or the cold external air just penetrates and invalidates it. This is why internal insulation is often so effective, but it is the detail between floors, extending cabling/pipework and the reduced living area, that causes problems. But it will probably make the biggest difference. Just sorting mine out almost halved my energy usage, and all I really did was improved the sealing of my existing windows and doors (finally sorted the front door after 16 years, almost). If you can get airtighness sorted, then you can fit MVHR, and get an extra bonus on reduced usage.

My nearest Metoffice station is reasonably close, but as it is so cheap to add an external temp/RH/air pressure sensor, it would seem silly not to. I like the idea of using others data, especially if it is prediction of the next days weather, but I am sure that can be worked out well enough locally (my cheap weather station calculates the sky conditions from just temp, RH and pressure, and is amazingly accurate. I wish I knew the algorithm then used, but never managed to find it. Knowing the weather for the next day would be useful as I am on E7, and down here the temperature can change rapidly in a few hours.

What happens when you loose connectivity?

Do you know your winter heat loads/gas usage. This is the important one for sizing any heat pump. If your annual usage is 41636 kWh, and assuming that you use 4000 kWh for hot water, that leaves ~37,600 kWh for heating. Now the coldest 4 months will use 2/3rd of that, so ~25,000 kWh, which is about a 9 kW heat load. It is usual to oversize a heat pump, though less so for a GSHP. So that 12 kW Nibe ones seems, on the face of it, about the right size. But £44,000, think about that, it is about half the price of my house. Or a very nice Tesla Model 3, which will save you more if you do decent mileage. This only leaves you two choices: Improve the building Gas If you want to improve the building, look at airtightness first.

Yes, and epsilongreedy, then see if we can get this topic up to 1000 pages. And you will still have a constipated pot.

https://improvementcosts.com/costs/roofing/home-roofing-cost/ Are you using Phillips Moss as your builder.

They never do for you, but that is because numbers are for the feeble minded and are just made up. You have to pick the right system components, not the most expensive tile replacement types.

I would still try very hot water and a stick. Or isopropanol, or even meths.

If it is PVA glue, just keep dunking it in hot water, and poke something down the hole.

I think that is a challenge to get the creative BuildHubbers to come up with a simple design that can be made by just about anyone, with basic tools.

Air is a fluid. Don't anyone, ever mention that MVHR can be noisy at night. And it uses electricity, 24/7. [getting my tin hat on, then me coat]

Ah, reminds me of holding my mother's hand, as we entered the slave trading city of Bristol.

Not very big for a gym.

Grown ups have gone to bed, we can get up to mischief now.

Tis tonight. What is cutlery?

But I am West Indian, 6' 2", and very strong.

And with Newlyn as a backdrop.

@pocster Guess what I am holding in my hand?

Useless tool

So you can get a spanner on it. Short one first, then the long one. Spanner.

But that polystyrene ICF is, yes?

Probably because in the UK, the climate climate is against you.

GRP, works every time for me. There does not seem to be much actual glass area in that design.