JohnMo

How do you stuff 10 people into 165m²? Are they all on camp beds?

Your 300L just isn't big enough for that at heat pump temperatures. With 10 people in the house DHW will be the dominant demand for 95% of the year. Are your quote companies aware you have 10 people in the house? Ideally you would size radiators to flow same temperature as the UFH and have a single flow temp and no mixers. Not sure what this is?

Sounds like a bodge - not a Just find a better location or a different delivery method of cold air

You can get various grades of mineral wool or fibreglass, something like Knauf Frametherm 32. I used multifoil in a summer house supported with loads of other insulation material. Not sure it would find a place in my house.

That is for under sizing the heat pump. So in extreme weather if after a given time not reaching flow setpoint it will fire the immersion. The heat pump will manages itself in those circumstances, it just starts the circulation pump on a continuous or intermittent basis based on outside temperature. So your heat tracing isn't really doing anything.

Do you actually think this is a serious thread? Good guess it's someone just flinging daft questions about. You can buy a 2.4m long worktop from B&Q for £60.

If they can't afford laminate - no idea why anyone thinks stainless is affordable.

Wouldn't you just be better fixing the half arsed job left by others. Been involved in lots of poorly installed heat tracing in my past. Heat tracing that isn't extremely well insulated, may as well not be there. Even with insulation you need to have suitable Watts per metre rating for it to be effective. Was this all calculated or was a stab in the dark? What powers it in a power cut, so does it actually afford any protection? Or is a sticky plaster that isn't really needed and isn't very effective?

But how many hours do you need and how low below freezing Nice simple to read article here https://renewableheatinghub.co.uk/do-air-source-heat-pumps-really-need-glycol/

Run my system without glycol and without anti freeze valves. Why do you need either? Both are there to protect the heat exchanger in the ASHP casing from freezing. It's a big chunk of metal that will not freeze easily, it's also insulated by the manufacturer and in a casing. It isn't freezing any time soon irrespective of temperature outside. Are antifreeze valve or glycol used in external oil boilers - no. Other disadvantage of anti freeze valves. Is they are directly exposed to air, so will activate way before any damage would occur if heating is off. Once activated you have drained out part of the water from your heating system, how do you fix if you are not hands on and your plumber isn't available?

None, materials and labour contract should be charged at zero vat - I assume a barn to house is zero vat

Not water proof or water resistant. External ply would be better. Or don't bother use and old door or old table, get inventive.

Most airtight expanding foams only expand a little. Someone will come along soon and give what makes and types to use

I would scrape out what you can and replace with a good airtight expanding foam. The foam will discolour with UV, but generally not an issue, especially as we move to winter.

Just have proper ventilation, then you have very little issue. Mould will affect the grout as well if your ventilation isn't adequate. Do a proper job, overall, and that includes correct ventilation. A simple dMEV fan and your ventilation is sorted. A Greenwood CV2 (£50 on eBay) or CV3, job done.