JohnMo

But what is different - an UVC can do just the same functionality for a 1/3 of the cost of purchasing a cylinder instead of a sunamp? What am I missing?

Or down 2 if you start to melt

I would add an electric towel rail in to the bathroom as well. Other than that it looks good to me

Are you sure, mine is devoid of aluminium layer. Could you run 15mm inside it? That would reduce the lag

Anyone with a GSHP does it every day.

Think you may be confusing car glycol with that used in heating systems. Car poisonious - heat pump heating system food grade.

First question is your installer proposing a buffer? If so could deleting that free up space? Slim line cylinder in a corner? Loft or space outside for an insulated shed? Hybrid, heat pump for heating, a combi boiler for DHW

Little confused, you have said you are doing a passivhaus, there is nothing passivhaus about 0.18. You need 2.5x the depth with insulated concrete compared to PIR. Kingspan is just a brand name, plenty of competition in the marketplace. I bought online, it came direct from factory. I would limit my choice to either 300mm EPS, slip membrane, UFH pipes, the screed or concrete, circa 100mm will allow you use as as storage heater, thin more like a radiator. Or 200mm PIR in 2x 100mm staggered layers. Then as above. If you are doing UFH aim for 0.1 U value

Once you get to low outputs and flow temps below 30 or so you cannot notice. I didn't go under any kitchen fixed units, showers or baths, kitchen islands or beds. A Lot of the, "you better do this or that", only really applies to UFH installed in very high heat leakage houses and/or with little or no insulation below the pipes. Well insulated with heat output of 15W/m2 and below, you can do just about do any centres, any pattern, flow temp varies only by a couple of degrees.

They have been that price for quite some time.

I had some high and low areas., low self leveling compound. High an angle grinder attachment from Screwfix and a Henry hoover (lots of bags), then some 2 or 3 days grinding away.

My justification was, I am earning, if I don't spend on this, it will go on rubbish elsewhere. The spend now, while I can afford it, is a reduced utility bill when I can least afford it - retirement. It's a better return than a same money in a pension pot.

We just have green plasterboard, then tiles. Never seen why you need to tank. Every house I have lived in, has been the same (since the 80s).

That is one overly complex roof. I would be tempted to look at this the other way around. Ignore what's inside the house. So the roof will have insulation above the steel work. Now the only part exposed is that which is overhanging outside. Insulated the overhang steel, much smaller area, you can have a flat ceiling.

Not sure they recommend that

Looks pretty similar to what I did. Put loads more pipe in bathroom. I would do as close centres as you can.

Believe so

We have PV GivEnergy all in one. If battery is full and I start to export this picked up by the PV diverter and that electric goes to the immersion. If I was to get an electric vehicle I would just get a GivEnergy charger, then you can control better how it all works together.

Spray foam depends on a few factors, vapour open or vapour closed. Retrofitted to a cold roof rafters to help hold the roof together is bad as pointed out above. New build no issues, as you can design for it. Interstitial assessment is a must for spray foam same, as with any other means of insulation. Scottish regs require us to install sarking boards, these are installed tight together and as the wood dries it leaves ventilation gaps. Above this a suitable breather membrane is installed. The foam used is vapour open. So any moisture can migrate outwards. The slates attached to the sarking boards, provide a ventilation space. Below this it is ideal to install a vapour closed membrane.

Nothing technical wrong - you gain a max of 5mm compared to PIR, but at the same time state to use a 45 to 50mm packer. Your money, your house, just trying to save you a few hundred pounds, on wasted materials.

You have 10mm of aerogel, PIR with the same R value is between 13 and 15mm depending on its spec. And you are adding 40 to 50mm packer, the packer is providing 3x the thermal resistance of the Aerogel - so why bother with the aerogel, just use PIR, it cheaper, easier to work with.

My first array is at 45 degs and roof mounted - dreadful output in winter, not helped by trees and low sun. Our second array is ground mounted, but vertical, provides 200% the output of the first array in winter.

Well I suppose this thread has run it's course then. You know the issue, unwilling or unable to change your ways. The other option is to throw the consumer protection option of "it's not fit for purpose" flag and demand its fixed by the installer, he would then get the manufacturer involved formally. Sitting on your hands, saying I know the issue and procrastination doesn't fix anything. Running high temperatures with lots of trv's doesn't help either. I will now bow out of this thread.

Really would you waste your money on aerogel and the then support it with PIR. The PIR on its own is doing the job. 10mm Aerogel is really adding nothing to reducing the thermal bridge. Just use 60mm PIR or deeper.

Our unit uses volt free momentary switch and it starts a rundown timer. But once the house is dried out, you really don't need to boost. Something smelly in the kitchen we boost, and maybe when having the annual bath, don't bother after shower.