ectoplasmosis

Another shot. Difficult to see, but it's a creamy off-white in real life.

I used Lime Green Natural Lime Mortar for our extension below: https://www.lime-green.co.uk/products/lime-mortar/natural-lime-mortar Comes in bags, just add water. Loads of colours; I used 'Chalk'.

EDF FreePhase. We have averaged ~16p/kWh over the last month: 7kW Vaillant ASHP, no solar or battery, maintaining 21.5C indoor temp 24/7, no setback at all. We ignore the 4-7pm peak except for load-shifting the dishwasher & washer/dryer overnight.

Apparently Hitachi's parts, warranty and engineer support is almost non-existent in the UK. This would make it a complete non-starter for me.

These are great, I used them to fix the T&G plywood flooring in my loft. Tiny heads which become almost invisible, and easily removable should you require.

I have a load of these around the house, they work very well. The phone app is very convenient, with graphs over time etc. They come with crappy AAA batteries that last a couple of months; replacing with decent quality alkaline AAAs lasts ~6 months for me.

Your 40C flow design temperature will be met at the outdoor temp design temperature, i.e. depths of winter. All other times, the system will be modulating the flow temp based on the weather compensation curve. If you “always wanted no more than 35”, then you should have conveyed this to your installer and they would have sized the emitters for a 35C design temperature instead.

Would love to know more about your project!

As several have tried to suggest already: your best bet is to get the installer back to balance your system. It’s not that difficult to achieve. You don’t need to add or change anything right now. The system needs to be balanced and commissioned properly. Begin with this goal, and see how you go.

Why do you want them to be controlled separately? All this would do is decrease efficiency, and increase the risk of defrosting problems in winter due to lack of water volume. Your current setup, with open-loop and no TMV or secondary pump on the UFH, is best-practice for achieving best comfort and efficiency... providing that the emitters have been sized/specified correctly! From everything you've said, it sounds like the system is probably designed and installed well enough, but the radiator circuit has likely not been balanced/commissioned fully, causing the rooms with radiators to undershoot the target temps. I'd advise getting the installer to balance the whole system, then tweak the heat curve setting to achieve suitable flow temps which keep all rooms at their intended temps. I really wouldn't recommend installing any kind of zoning control, or thermostatic mixer on the UFH, this would only increase running costs.

What is the 'room stat'? Do you mean the Vaillant Sensocomfort controller? If yes, which weather-comp 'mode' is it set to (Active/Inactive/Expanded)? What type (K2, K3 etc) of rads do you have upstairs, and how big are they in relation to room sizes? You should have had a 'radiator schedule' document with these details as part of the install/commissioning process. You should not have to fit a TMV or auxiliary pump to your UFH circuit, providing the radiators have been properly specified. My house has UFH downstairs and rads on the upper 2x floors, no mixing valve, single flow temperature. Works perfectly, whole house stays at a constant 21.5C.

You'll be gaining a dry pipe! Don't know why it's so difficult to grasp... Just fit the pipe lagging, and stuff a load of mineral wool into the hole until it's flush with the pipe lagging, job done!

We have a GU Secury auto-deadbolt 4-point lock; no handles outside or inside, slam shut, opens via the Euro cylinder key. Works really well.

Whats this stuff like? The price looks good, but how long will the adhesive last?

Lots of data here: https://community.openenergymonitor.org/t/vaillant-maximum-output-capacity-testing/27221