Posted by: @jeff

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It is not clear to me that you have a clear idea of what you want the final solution to achieve in terms of the conservatory? Perhaps you do in your head, but it doesn't come across in your posts.

I am also not clear on how much you use the conservatory through the year, how important is it to get it right.

My late mum had a lovely large conservatory on the back of her bungalow. She used it almost as much in winter as in summer I suspect, with a large double radiator in it. It had sofas and a dining table in it.

Ironically perhaps is was the most important and well used part of her home.

I can't tell how important the conservatory is for you, albeit you mention it many times.

As another example, the in-laws a have smaller conservatory that they have just had an insulated roof put on to replace a glass roof. It is now much cooler in summer, but to be honest they still hardly use it and it has a couple of cheap wall mounted convention heaters.

I wonder if you were clearer about what you want to achieve with the conservatory and how you use the home overall then it may be easier to compare solutions albeit there may still be a lot of variety across installers?

Interesting points, and I can see why you'd think this as the clarity on the conservatory has developed through the course of the quotation process.  It started as a non-issue until the first surveyor, from Octopus (who was also doing the EPC), mentioned it as soon as he walked through the kitchen door and spotted it.  At the end of his survey he said they could treat it in two ways, either as a habitable heated room with a target temperature in line with the living room, or as a room with a lower target temperature (16C, IIRC).  At the time he almost steered me towards the first option based on the fact that I'd told him that we occasionally used it as a dining room (e.g. on Christmas Day), and it's factored into the Octopus quote in that way.

Subsequent to this, other designers have treated it in different ways, based on my discussions I've had with them.  EDF initially discussed using TRV's to reduce the heating requirement in there when not required, which I liked the sound of, but then when their design team got involved they simply removed it from the planned system completely.  It took 24-48hours after this discussion for me to realise that I didn't like that option at all.  Since we moved into the house, the conservatory has been controlled by a separate thermostat to the remainder of the house, and it has been an irritant to both my wife and myself that it has, so I've concluded that I don't want it to be separated, even if there's an efficiency cost to doing so.

In the visits that took place last week, I've been able to discuss this with the surveyors with more clarity, and all have planned it into their designs, albeit with the fact that I'm relaxed about it being treated as an occasional room (one of them mentioned that there's a classification they can use in the MCS specs, but I can't recall what he called it, but it sounded like a good workaround from a design perspective).

We've also commenced a process, as a direct consequence of the heat pump exercise, to get quotations for updating the roof and/or glazing in the conservatory, which will ultimately reduce the heat loss within there and make it more like a normal room in the house.  This may be via simple replacement of the roof panels with an insulated version, or a more complete replacement of doors, windows and roof with building reg certification which would enable it to be treated as an additional room in the house (and enable the external doors to access to be replaced with an internal door, which we didn't even realise was a restriction of the current set up).  Consequently, it's strengthened the view that including the conservatory is the right option as it will ultimately become less of a heat loss challenge over the life that this installation will run for.  If it's a design compromise at the point of install, it will become less of one at some point in the next year or two.

We have a summer house connected to the main house heating. The initial idea was to have it heated all the time, same as the house, but it soon became obvious the heating was really running only to keep the summer house warm. So plan 2, the more pragmatic approach, let the house dominate and the summer house get what it gets. So summer house floats over about 4 degs (17 to 20), if we want it hotter we just flick on a panel heater.in the summer house.

If you only use at say Christmas, just heat to 16, if need add a panel heater, or have it unheated, to get a realistic ASHP size, not dominated by an occasional use conservatory.

@sheriff-fatman the conservatory probably had a separate thermostat fitted to meet building regulations. Officially they need a separate thermostat but rarely do...

https://www.theconservatoryheatingcompany.co.uk/news/conservatory_heating_building/

You will find lots of conservatories out there without external rated doors and with TRVs only to control the temperature... some even open plan to the house.

My late mum had an external rated kitchen door and external rated living room patio doors into the conservatory but just a TRV on the radiators for example. No issues when selling the property in terms of EPC, survey, mortgage, insurance etc. So although officially a requirement it doesn't mean a lot in all the examples I have seen. Not to say you shouldn't comply with the law.