Radian

I can only tell you that with my Daikin A/C units the Onecta app shows actual room temperature/humidity and setpoint in those locations:

Like @nod say's, step up the DPC either side of the doors. Some knuckle heads think a door is a wall. It isn't and it's not bothered by rain splashing up unlike masonry.

I always put the cavity as being at the rear ventilated level (outside air) because most janky builders leave walls like sieves. If I make that installation level, it drops to 0.254 which puts my calcs either side of yours. The Knauf Insulation was only available in 80mm so that helps them. Couldn't be arsed to find a 75mm batt. Either way @Russell griffiths has to win the pint.

U-value: 0,267 W/(m²K)

Is there no plan to tile this area? It looks to be set up perfectly for quarry tiles or something of a similar thickness.

Two things: You might still be able to get boiler flow down a bit, try 60oC (every little helps) the other factor is time - you don't say how long the UFH is programmed to be on at the 18oC set point. If this is less than 24/7 you've still got a control to tweak. If it is 24/7 you've got a big heat leak there and either give in and use additional space heaters during exceptional weather - or revisit your floor makeup as you said.

I just knew it'd be messy!

If you don't take steps to remedy it, I would expect this to be a permanent source of condensation leading to mould. You could start by inserting your scope into a diagonally drilled hole a little way from the frame to get you into the junction between window frame and outer leaf of wall. Do it about half way up the bit you marked on the photo BUT MAKE SURE YOU MISS THE FRAME! You could make thigs much worse if you breach the hollow frame! Alternatively, have a good look outside to see if there are signs of the frame being jammed in tight to the reveal. If it turns out to be a tight fit you shoud get your installer to come back and sort it out. If it's stood off with packers it's just down to the state of the reveal which probably means cutting it away and re-boarding to remedy any cold bridging. You could certainly try injecting foam and seeing if it helps first, but how effective it might be would be anybody's guess.

How about getting a length of 160mm or 110mm drainage pipe (depending on what would fit best in the liner) to come out flush with the finished wall. Then use illbruck fm330 to foam around it. I'd mask the wall first and cut it back when set and skim over. A round or square grille to finish.

So your's is this DG unit with MDPE thermal breaks. Very good performance across the broken sections I expect but laterally you have UPVC bringing the cold directly in from your bridged reveals. Maybe the frame is a tight fit into the reveal at this point?

Hadn't thought of that! Messy though, and could be harder than you'd imagine. Does it even retain it's fire protection if broken up I wonder?

Been around -3oC this evening but just noticed it's rinsing quite fast. Down on the tip of Cornwall it looked, for example, like +5oC in Penzance at the time.

You're about 8oC warmer than us here along the South coast. I'd be looking at something hotter than Battenberg. Something with Bacon.

What? No salted caramel?

Tricky one. And welcome. Unfortunately the battens are a cold bridge that will hold you back while they're still there supporting the T&G It all depends on the percentage of insulation being lost that they represent. Definitely worth doing an analysis of your build-up if you can characterise it sufficiently well to put the details into a calculator like ubakus.com If you did go for floating PUR floor (and with only 50mm available, rigid foam PUR is the only insulation worth going to all the effort for) you can level the screed with sharp sand which will add the absolute minimum.

An important bit of psychology it would appear. I tried increasing the hysteresis by 0.5oC to reduce boiler firing frequency but the occupants perceived this as a reduction in indoor temperature even though the average was identical. Cold radiators were the most often cited case for the prosecution.

It wouldn't be cost effective to get them out here and set up - just to blow a cubic meter of beads. On the other hand if I could just source the beads, it'd be a doddle to do myself. That's right. The differentiation in availability between loose beads and solid sheet seems very odd to me. I suppose it could be because these days it's routinely injected with a PVA bonding fluid as @PeterW points out, which is certainly desirable but not essential for DIY. My rental property has un-bonded beads put in nearly 40 years ago and gets along just fine. R-Value of vermiculite doesn't look as good as polystyrene but perlite looks more promising: vermiculite 0.366 polystyrene 0.4 Perlite 0.475 (comparative figures for 1" thickness)

The conventional arrangement is a bit weird to me. A frost stat trips on low temperatures to protect a boiler located in an unheated space. Fine, and some boilers incorporate this sensor inside the boiler. But external sensors won't necessarily be heated by the boiler, like if they're 5m away. So why is the conventional solution to this to add yet another sensor (pipe stat) on the return flow instead of just mounting the frost stat on the return in the first place?

That covers geofencing and window open functionality. I'm not seeing anything to get really excited about. You surely must have remote control of temperature on the free app?

I've lived here for 25 years and never once so much as put a screw into any of these boxes. However, in the extremely unlikely event of me wanting to gain access, I'd get out the garden vac and suck 'em out ready to re-fill. If it's someone else's house, I'd consider it an excellent posthumous practical joke. Do you have any other suggestions for how to retrospectively insulate the voids around these stacks?

I don't want them to put in a wall. As I said above, I've got three boxed-in stacks that I can access from above and I just want to pour in beads to get the insulation all the way down to the ground where I know there is none.

Sorry, yes, I should have elaborated: a supplier with a retail facility. I mean, it's easy to find furnishing grade EPS beads all over ebay and Amazon but claims of fire ratings are highly dubious for a plain white poly bead. Funny really because graphite EXP sheets are readily available from those places as well as insulation stores. On their website it says "We also work closely with a selection of builder’s merchants and retail suppliers." but I'm still waiting for a callback. I don't hold up much hope as without retail sales it usually means f-off unless you're in the trade.

I always smell a rat when something doesn't come up in a google search - I want it, I've seen other people say they want it, so why isn't it on general sale? We recently had our cavity walls injected with graphite coated (fire retarded) EPS beads and the big old box-van showed up with around 12m3 of beads in a built-in sack. The van is mostly just a big sack of beads: So I'm thinking that these would be ideal for pouring in around several boxed-in stacks that I've got in the house. But can I find a supplier for them who won't only show up in a van and pump them in? Can I heck. Anyone know a way to get hold of them?

Ffs. A subscription to get optimised control from the heating control device you've already paid for?

If you're in the UK, you probably wouldn't meet building regs Part L (U-Value <=0.18 W/(m²K)) I would suggest you should aim for better than that anyway seeing as you're starting from scratch. 150mm Celotex might get you 0.15 W/(m²K) for instance, but there are other types of insulation to consider.