JohnMo

Where does the duct currently come into the room for your extract? Plan of the room would be helpful? Showing shower, toilet, sink, and duct entry.

Salus do some nice thermostats (quantum), you need their ZigBee gateways also. But most equipment tied in to the internet has a short life, I try to avoid, especially with heating and ventilation.

The other option is two ducts, one supply the other return. Use 110mm twin wall flexible duct, Hep2O pipe or similar, with 25mm thick Armour-flex. Seal the ends of the duct as it comes out the ground spray foam and stainless steel mesh. Still a pain to bury but less so than above.

I would be tempted to leave it vapour open, and use a mineral wool, something like Rock wool Flexi or similar. It's nice and stiff and will self support and you could over fill with something like 150mm. To get similar U value as 100mm PIR.

Not sure you need to complicate MVHR with HA. Mines been running at a set speed for the last year, occasionally boosts manually if we have some smelly cooking. From all the things you want to automate, not sure you 'really want' it simple. Simple is light switches, door keys and possibly remote switching of blinds and gates. What happens is 5 to 10 years when you need to start replacing strips?

None of them are that new, CO2 has been around for quite a while; but is high temp at a very defined flow rate, next to no modulation, a bit of a one trick pony. If you hang about for the so called next best thing, you could be waiting a lifetime. Nothing wrong with the current ASHP offerings, either R32 or propane. You can spend as much changing from one heating system to another as you spend on the heat source. Is an electric driven heating system the right technology if you are fully off grid? Think that may be a better question

Not sue if you found a resolution for this. I did a training course for G3, took a day at a local college (I'm not a plumber by trade) and you can then self certify for yourself for 5 years. Get the plumber to do the leg work and all the plumbing, you oversee it and sign off. But if the plumber is G3 certified, he's G3 certified, he just cannot register the install via the gas safe register. Talk to the council planning people, tell them the story as your previous post. If the council needs the install registered (ours doesn't and isn't interested), he can do it direct with the council for a small fee.

So a little left field, could installing a dMEV fan in that location simplify things, it could be placed high up and extract though the roof or the block work wall?

We did Sarnafil EPDM with decor profiles, to replicate standing seam. Around £15k for 200m2.

It's only just a EPC B by one point. Everything is just too big...and cold looking.

We were signed off in March (Scotland), no issues. We have a low profile shower tray, about 20mm, the floor tiles butt up against the shower tray, so in theory a step of a out 10mm. However the door frame has a 50mm high cross piece at the bottom, giving a step. Still no comments at sign off.

You need a deep foundation for that, nearly 4 times as deep as PIR!

I use one of these, induction hob, oven, lights tv at same time no problem. Our 6kW ASHP no issue. But your heat pump is bigger so idea. https://hyundaipowerequipment.co.uk/p1pe-p10000le-7-9kw-9-8kva-recoil-electric-start-site-petrol-generator-powered-by-hyundai?gclid=CjwKCAjw69moBhBgEiwAUFCx2Fbz7H-U8e087ep8aNj5WsMWeXQBVip-bHh7G5iLfnaQfHVlSxUlphoCSAQQAvD_BwE

Especially if you are core drilling through block work, when the room is finished and furnished. I say do it all now or don't bother at all. If you don't do it now fully insulate the chimney and seal off. Get a fire backet and some logs and make a feature of it, knowing you will never use it. But if you really wanted too you could, with some mess.

If I recall you have a thick slab, so heating times could be reasonably long, i.e. most of the day at a low temp. Or you could run a slightly hotter and batch charge. If you had E7 or time of use tariff just charge during that period. All you need a 0.1 hysterisis thermostat. My UFH is in 100mm concrete, and everything takes 6 to 12 hours (heating and cooling down again). Problems you may have is short cycling if you try to run it independently of the rest of the heating system. Think you are the same as me, no buffer. The very simplistic approach with least risk of short cycling is to run it all together UFH and rads as a fully balanced system. If your wireless thermostat has a hysterisis of 0.2 or above I would get something better other you will get big overshoot or undershoot of UFH room temp. Or could you run the radiators on WC, with night setback, so the bigger part of the system is on most/all the time at lowest flow temp, and just have the UFH doing its own thing on a 0.1 deg hysterisis thermostat driving mixer pump.

I would talk with a stove installer, get the correct liner installed now and blanked off. Then discuss how to insulate, you may need to fill with vermiculite or similar. Not sure how you get access?

I ran my ASHP yesterday more on purpose (finishing off commissioning as ASHP was installed at the start of summer) than a need. Ran it for about 7 hours, the electric meter recorded about 2 kWh of additional electricity use, at yesterday's temp the CoP would have been circa 6.2. Just looked back at my gas usage for last year, it was a bit colder, but a typical day in late September used 21 to 25kWh of gas. So 7p X 21, so about £1.50 at today's costs, while the ASHP was £0.60. If you have PV and run the ASHP in the shoulder months, it's cheaper than gas. If no PV it compatible to gas down to about zero degs.

Not sure a chimney is a wise choice. Ideally with modern well insulated and assuming a reasonable airtightness, the chimney goes against all that. Your log burner, stove, really needs to take primary and secondary air from outside the building, so an air duct will be required, otherwise your are adding air bricks etc. I would assume whatever you have done may not be suitable for a stove, I think you really need to talk with stove installer now rather than later, making changes now is easy, later you are pulling your finished house apart.

Fine tooth wood saw, and get on with it.

That makes sense! Thank You for clarification.

I just converted a normal towel rad to electric only using a Termo One thermostatic heating element. The package comes with an adaptor to dual fuel (water and electric), so you can install the element and tie in the water pipe.

Towards the bottom of the page - what a buffer is and what it does

Ask them for a full door/window U value calculation (Uw), if they don't/will not supply be careful. They ae not telling you something - like the window frame is rubbish thermally, so will make the Uw rubbish no matter the Ug is. The only figure that important is Uw but most suppliers only want to give out Ug. Uw - mean whole window or door set U value Ug - glazing U value only

Assuming the heat pump is weather compensated, you could just balance that radiator, to prevent over/under heating. If it gets too hot close in the lockshield valve a little until heat in matches room loss.

Made by Gledhill, only differences between a Gledhill and Ideal Heat Pump cylinder is Ideal supply a 3 port diverter, and Gledhill a 2 port valve, the temperature thermostat is different. I changed mine to a digital dual thermostat for £15. Most heat pump installs will have a thermistor tied direct into the heat pump.