-rick-

£70 a month (£840 per year) no, as I've said before I think there is a decent improvement to be had for not ridiculous money. As I've said my mums uninsulated house with an inefficient gas setup and various other problems costs about £2000 per year to keep at around 20 during the day but they let it get cold overnight). I do think it's possible for zoot to be much more comfortable for an affordable amount extra per year, at least as a trial. If zoot has money to consider ripping up his concrete floor and replacing it he has the money to try this. Maybe he doesn't have it to run long term but having the information about what it takes to warm the house can direct him to the most cost effective improvements to lower those bills. Right now it's finger in the air guesswork. I've not given up yet but I do understand where you are coming from. I hope zoot will agree to try it for a period of time. If it works then we can have a conversation about whats next. But fundamentally zoot doesn't believe this stuff and words on a screen aren't going to change his mind. Being warm in his house might.

It's a lot of money to do that. Zoot hasn't been hugely clear on his financial constraints but given he got his heatpump installed through a low income support scheme I think it's reasonable to assume an AGA is off the table. Zoot did have a woodburner, that has also failed to heat his place. I tend to think the heatpump can work and would be cheaper to run than an aga but only if used in a very specific way and one that zoot is very resistant to doing.

It's been asked for repeatedly. There should be two of them. One from the original install and one from the monobloc replacement. Unfortunately a lot of things get missed in this thread. There is so much going on I can understand why.

Phew, far too much technical jargon there. I'm struggling to keep up! 😜

No sounds very much like your body reacting to the very bad environment of your cottage. Unless you weren't spending any time at all in the cottage (you say you were in and out) then it's likely your cottage. I wouldn't be surprised if your health is degraded even now living as you do. You've just got used to it. It's one of the reasons I'm putting so much effort into trying to persuade you to warm your place up. Having a warm home will extend your life and help you be happier. With your home as it is you are one unlucky infection away from ending up in hosptial or worse.

Serves me right for being lazy and using the first random website with a humidity calculator on it :) 53.6% is indeed perfectly fine indoors. 45-55% is ideal IMO

What I explained is proven science. If your idea of how something works doesn't match well established science then either you've made a major discovery and are in line for a Nobel Prize or you are wrong. https://en.wikipedia.org/wiki/Humidity And? In winter the outside air may have a relative humidity of 100%, ie, it can't go higher. The amount of moisture in inside air assuming you warm the building is almost always higher than the amount of moisture in cold outside air (because humans breath). If your building is at 20C and you open the door, let in a load of cold, moist, air and then close the door you most likely you will either keep the internal moisture level the same or LOWER it. You will also lower the temperature, but if the building fabric is up to temperature (as I am suggesting) then this temperature will return to the previous one very quickly. This is not how it works, the amount of moisture in cold outside air will not introduce moisture, if anything the opposite. You misunderstand humidity. No. Dehumidifers are generally there (in the UK) to remove moisture introduced by human activities. Washing, breathing, etc. In countries where the outside air is hot and humid and they use internal air conditioning to cool the temperature your description would be right but not in cold UK. If your microclimate has 100% humidity during the winter that isn't significantly different to my climate in london where its about 80% humidity in winter. My inside humidity is 45% even though the outside humidity is 80%. How? I heat my place. I don't have a dehumidifer. If you have a warm house you will feel dry*, the warmth 'dries' the air (the amount of moisture in the air stays the same, its the relative humidity that changes). * Assuming you open the windows regularly to blow away any moisture from breathing/washing/etc or have mechanical ventilation. It's a complete misunderstanding of how things work. It may feel comforting to have the excuse as to why you are cold but that's all it is, a story you tell yourself. I understand this is difficult, especially when others around you say the same thing, but this is the thing with stuff like this the comman man in the street understanding of the way the world works is often wrong. Our modern world wouldn't exist without the scientific understanding of how humidity, heat transfer, etc, works. People cleverer than us have figured this out decades/centuries ago.

This is bollocks. Here are some cold hard numbers. Maximum possible humidity is 100%. Assume your outside air is saturated (100% humidity). Assume its 10C outside. If you heat your indoor space to 20C the air, holding exactly the same amount of moisture will be at 50% humidity, which is perfectly fine for an indoor climate. No dehumidifiers needed, just heating the house to 20C vs the outside air of 10C. If the outside air is 0C then you only need to heat to 10C to get the humidity down to 50%. This all assumes you aren't introducing more humidity into the air (which of course we all do as living beings) but the point stands. To solve humidity issues in a house, warm it up.

One of the reasons I have noted for insulating pipes is that the insulation can act as a buffer/decoupler from thermal movement and noise (assuming you strap the insulation not the pipes).

I have no confidence we can get your place warm during the day if you let it cool down like this overnight. Frankly I think it's a waste of time to try and help if you are not willing to consider higher. It might be possible that this will work during the shoulder months (ie, now) but it won't work during the winter. If you want to have 10C overnight then you would need to accept that the temp during the day won't be much higher. If your concern is noise, then that can be dealt with separately. With my bedroom door closed I can't hear my boiler running 2 meters away, I'm sure it's possible to arrange that for you as well. Even maintaining 10C overnight when its 0C outside will involve the heatpump working overnight. So setting 10C isn't a way of limiting noise. It's just a way of never being warm.

That would be an excellent result. When I've done rough calcs to see if his heatpump could cope I've used a U value of 2 (1.71 was the worst case wall looked at in the Scottish study I used and I rounded up to be conservative). Even with a U value of 2 the heatpump should be capable (barely) of maintaining the space at a steady temp.

I'm not sure your experience can apply to Zoot too well. He has a 9kw heatpump that will work most efficiently with relatively cool radiators. A 30kw AGA pumping out heat to the radiators at 70C will have a much easier time heating the air quickly for short bursts than Zoots heatpump. On the coldest days zoots heatpump might have to be working near flat out just to offset losses meaning no spare capacity to alter room temp. I very much hope that zoots property has better heat loss numbers than these worst case calcs suggest but without a more detailled information from zoot it's the best we've got.

Oh boy. Lots going on while I was away, not sure where to start. @zoothorn I'm glad you will considering moving the controller even temporarily. I know it sounds crazy to you but I think it's quite important for the thermostat to be in that cold room. It's possible this may lead to other rooms being hotter than you want but we can deal with this in other ways. We've gone round in circles about how you think your place is uniquely cold including statements like the above. It just doesn't stand up. I've checked, Slate has a higher ability to store heat than sandstone (they are pretty close). Earth is even better. You have a misunderstanding of how this works. It's a common misunderstanding but I feel that you've struggled with your house so long it's become almost a religious belief and you just can't believe it when people say you've misunderstood. I will try again below but even if you don't believe it then please don't let that belief stop you trying something different. People coming to your house express how cold it is because you've let the building go cold. Your very thick walls are very big energy stores and the temperature of them will change slowly not fast. When you put heat into the room, you heat the air first, but the walls stay cold. It takes the room being warm continiously for a long period of time for the heat in the air to slowly transfer into to the stone. If you turn the heat off then the cold in the stone quickly cools the air making you feel as if the place is just always cold. My whole goal of this conversation is to get you to try to warm the stone walls up. This will take a lot of time and energy, but once the stone is warm then the amount of energy use to maintain that state should be similar to the other uninsulated homes we've already discussed (more than you are paying now for sure). Once the stone is warm you will find that turning the heating off for a short period doesn't lead to the room quickly getting cold (if it does you have bad drafts that need fixing).

Ideally UVC should be optimally placed for short pipe runs to the bathrooms/kitchen. Wherever that is (up or downstairs doesn't matter). I'm sure others will disagree with me but UFH manifold should be central and if that's not where the plant room is so be it. Can be built into a cupboard/bump-out/etc. Does need to be accessible but can be remote from other plant (unless you want to do lots of zoning or other complexity which this forum advocates against).

Yeh it's not perfect but my thought was not to steal space from the room, just reorient the space. I'm not doing this with a ruler so very handwavy. There is likely room to optimise space use between the two bathrooms if they back onto each other, etc.