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I've just switched to Tomato Lifestyle, coming from Octopus Tracker. Switchover should be happening today... ASHP, but no batteries/PV/EV. Looking to load-shift the dishwasher, washer-dryer, and boost the ASHP set point during the 1am-6am 5p/kWh period.

As mentioned, having two boilers for your kind of heating system is madness. Ditch your 'installers'.

Except they won't be running anywhere near capacity, except for during a few of the coldest days of the year. Our 7kW Vaillant ASHP is practically inaudible day to day; the only way of knowing whether it's running or not is to feel for the airflow. It's MUCH quieter than the neighbours' gas combi boilers.

If you get the wireless version, then you can stick that anywhere you like, even move it around depending on how you use the house.

“Thermost.” would be equivalent to Expanded I would have thought. You would need to have the VRC700 in a habitable space however; the temp sensor wouldn’t be doing much stuck in a utility cupboard.

Done

You have access to the exact same settings on your VRC700 already: “Room Temp Mod”.

On the SensoCOMFORT controller, just configure the ‘room influence’ setting to ‘Expanded’. This will switch off all circulation pumps once the internal temp reaches your chosen set point. We ran like this during the summer, then switched to ‘Disabled’ mode once the heating season started, which enables pure weather compensation with the circulation pumps constantly running.

That insulation product won't be doing much of anything I'm afraid. With your current plan, it will be very expensive to heat the room. What is the current ceiling height? Could you add 100mm PIR insulation underneath the electric mat? If not, then as mentioned above, an air-to-air split heat pump system will be much more effective and cheaper to run.

50degC design temp is too high, you should be aiming for a maximum of 45degC. Our MCS heat loss calculation document and associated emitter schedule had radiator Watt/BTU ratings listed at Delta-T 50 for ease of comparison to manufacturer's specs.

No, we looked at the Cortizo 20 sliding doors as part of an extension/retrofit. Visited a couple of installations and I wasn't impressed with the design. They look great though! Ended up with Velfac casement doors and opening picture window. Seals are very good. I've attached a pic.

I can't advise on installers, but having experienced the actual product (sliding doors with 20mm sight lines), I was not impressed with the design. Thermal bridges everywhere, sub-optimal seals and a poor threshold design which leaks air.

Everything is plumbed as a single open zone right now, single Vaillant controller running in pure weather comp mode, no buffer/volumiser/low loss header. Rads have been balanced. There is however a stat on the bathroom UFH loop set to close the loop if the temp in the bathroom reaches above 25degC, as there’s a large dual fuel towel rad in there as well, but the bathroom loop is tiny.

Thanks again. The entire system is new, and has been designed around a 45deg max flow temp at -3deg OAT. If I were to remove the blending valve and secondary pump, then run the whole lot as a single zone at the same flow temp, would this work well?

Thanks. If I set the Reliance thermostatic mixer valve to 55degC, which the flow temp will never reach, will this act as if the mixer doesn't exist? Or is the best approach in terms of efficiency to physically delete the mixer and secondary pump?

I have just renovated a Victorian semi, and fitted a Zehnder CA 155 WM MVHR unit. I'm looking to upgrade the standard 'G3' grade filters, but can't find anything finer than G4 for the CA 155 model. Would upgraded filters from any other model fit? If not, is there a way of modifying/making custom filters? My daughter and I have asthma, so it would be great to fit F7 grade or better filters to deal with PM1 particles.

Can we see more detail of your terrace refurb in general? Very interested.

Thank you, very detailed and helpful. We don't have much time nor money left over to change anything right now. Will our current setup, with the Reliance HEAT970366, be OK for the time being? Floor build-up is 150mm PIR, with 100mm dry screed with UFH loops embedded, then Marmoleum lino as the finish.

Yet another thread dredge… I’ve just had a 7kW Vaillant Arotherm Plus system installed as part of a Victorian house retrofit, with 3 loops of UFH on the ground floor only (rads everywhere else). Design flow temp: 45degC @ -2degC OAT. The UFH was specced and installed by a separate plumber to the ASHP installer. They installed a “Reliance HEAT970366” thermostatic blending valve, which says the following in its specs: “Hot temperature supply range: 60°C – 85°C”: https://underfloortradesupplies.co.uk/product/reliance-water-controls-thermoguard-heat970366-ufh-blending-mixer-valve/ What does that spec mean? Have I got a blending valve that’s unsuitable for my ASHP install?

We’re looking at buying from them also, on the recommendation of a friend. Would you mind sharing the pricing you’ve received?

We’ve got two floors’ worth of habitable rooms being supported by the steels (Victorian semi with loft extension), so highly likely we’re going to have to coat.

This is indeed news to me; I hadn't considered not using intumescent paint. Is the need for it a question for building control or a structural engineer?

Thank you everyone, your replies have put my mind at ease somewhat, and are much appreciated. We will of course be coating the steels with intumescent paint, then a top coat to complement the rest of the interior. All the steels sit inside the thermal envelope, aside from penetrating the floor to the footings. I’ve had standoff ears welded to the uprights to accommodate the IWI, plasterboard and finish thickness. Hoping it all works out!

We are having an extension built using a ‘goalpost’ steel support structure, with steel columns resting on the he concrete footings. The steels have already been installed, without any kind of thermal break material under the columns; they are resting on concrete pads and will penetrate through the floor slab, insulation and screed with UFH. We planned to leave the steels exposed, as a feature. We are wankers, I know. Aside from putting a 50mm PIR barrier around the base of the steel posts to separate the UFH screed from them, there’s not much else that can be done now. Are we in for a world of hurt? How bad will the thermal bridge to the footings really be? The rest of the steels will be within the thermal envelope. We aren’t building a passive house; this is an extension on the back of a solid-walled Victorian house, but we’re fitting ASHP, MVHR, EWI/IWI to most walls etc, so this thermal bridge oversight is keeping me up at night…

Instant modulation response, efficiency (directly and the exclusively heating the pan itself), better heating uniformity, ultra-quick water boiling, easy to achieve continuous simmering, no combustion byproducts, no direct fossil fuel use, much easier to clean… I was a gas evangelist until we switched to induction and capped off the gas supply; it’s a revelation, and I’d never go back to gas unless I didn’t have a choice. Note however: if you’re a big fan of authentic wok cooking, gas is still the only choice for now.