SteamyTea

That seems to be one of the most useful papers I have seen on the subject. Thanks (not that it addresses the original question here, with is about insulation and thermal inertia)

Who you agree that a cement based product, with the same properties as a lime based one would work just as well?

You can have some fun with this without being reckless with the customer's money. If that ceiling/rafter covering can come down easily, you may be able to hide some MVHR pipework up there and possibly a bit of extra insulation, though that would probably need to be hung below the rafters, so depends on headroom. I think this one, if your client agrees, is one for a blog, with lots of pictures/videos.

Explain please? Where does that very small number come from? It is the 5 sigma on the normal distribution chart. It is the point where Physists agree that the change it is something else is so small that it is if no consequence. There is Physics, the rest is stamp collecting. It used physical attributes of materials, just at a lower level, probably around 3 sigma. So 99.7% your designs are correct. That does not mean that if you build 1000 columns and beams, 3 will fail. Just that you can be confident that the chance if failure over a design life is too small to worry about i.e if you design for a 60 year life, and your materials are good for 100 years, you won't have a failure. Not really, there are still proper scientist trying to find holes in well established theories. It is often said that a Doctor of Philosophy spends 4 years proving something, then a lifetime trying to disprove it. (I am just doing a little experiment to see if something I think will not work, may work. Much of it is to do with my own bias, but I may uncover something useful)

This is how science works. Something is observed, a hypothesis (tentative explanation about a phenomenon) to explain it, then an experiment is created to either, and this is very important, falsify the hypothesis, and be able to repeatably test it. The falsification is the really important bit as that is where the statistical data comes in. All falsification does is reject the hypothesis, it never proves and alternative (which is where we are at in this discussion). This may seem like a binary choice, but it is by reducing a problem to either, yes or no, that the truth is found. This area of science has allowed us to delve incredibly deeply into problems, while also getting rid of the rubbish. Hypothesis are often referred to by lay people as guesses, this is very much not the case, they are based on existing knowledge i.e. which is more porous cement or lime render, how much liquid water, as a fraction of existing mass, can the materials absorb, is the render applied correctly. Once a Hypothesise is has passed the above tests to the desired significance, it becomes a theory. If there are no known exceptions, then it comes a scientific law. This is where science and mathematics diverge, in science, you can have a theory that holds true only 80% of the time as it is considered 'good enough for most cases', medical work is at this level, Physics works to a much higher standard, usually 1 in 35 million that it is not chance. Mathematics has to hold true, with no exceptions, in all cases, no matter what.

And the depth of the damp into the wall.

You would need to find out the fraction of moisture it can absorb. You don't want to be putting a damp sponge on your wall. Are they at the same orientation to South? What are the respective wall areas? Is the window to wall area, with respect to floor area, identical? Is one room used more than the other? What size heat emitters are in each room. And regardless of that, a greater thickness of any material will transmit less energy though it. So your 2 x 330mm wall will have a lower U-Value than the 2 x 220mm one. So it is a better insulated room.

Make infill panels stuck to the glass.

https://www.diy.com/painting-decorating/wallpaper-wall-coverings/sticky-back-plastic-window-film.cat?Effect+group=Wood+effect&Room+use=Kitchen

@Gus Potter Is this your on place, or a clients?

I assume you have some clothing on. So the insulation value of your clothes is keeping you comfortable. As an experiment, how about covering yourself in thick mud, letting it dry, and see how comfortable you feel. Get pictures posted up. As for evidence of love, love without evidence is stalking.

Can't really help, but have you considered adding extra insulation to other places. Doing that may get the thermal losses down to a reasonable amount and leave the thatching unaffected. Alternatively, improve the airtightness and run a large MVHR unit to get the moisture out, then you should be able to add insulation anywhere without worrying too much about where water will condense. I thought it was usual for thatched places to have roof fires when new owners took over.

@Mike Save me reading it, where in France? The climate regime may be very different from ours. The UK has quite a unique climate.

At least you thought about it and put a remedy in. I wonder how many people just spread clay and then wonder why they get some localised flooding.

Soft water has more 'spaces' for other elements to get into. Water is the universal solvent, and not always to do with the ph. Then there could be some cavitation happening because of the restrictivor. Cavitation is just 'bubbles of nothing', the damage is caused by the energy caused when water rushes into the cavity. Energy is mass times velocity after all. So a lot of little masses, moving very fast, can do damage.

I think that order is the important bit, from an ecological point of view. The only thing to be careful is if it is clay subsoil, water runoff could be a problem.

I hate to say it, but seems more like hopium than a solution. Is there any proper research as to the long term performance.

The problem is the velocity is too high. Can you put a small ball of chain in the gutter above the chain and hope it does not clog up.

I am reading with the assumption that there is no intrinsic difference in the materials. But seems from what @JamesPa quoted, gypsum is better than lime. Will just have to see where OPC mixes fit in.

Make sure there is plenty of insulation under the floor. Then add a bit more. Will your DNO allow you to connect up 7 kWp without special conditions? Worth checking. If not there are ways around it. That's kW, but could be autocorrect. WTF is that, a new one Kelvin thousand watts.

Which is a point I made earlier as well. Hopefully, tomorrow, I shall have a proper read of that PhD paper.

I hate wide monitors, but then I do have persistent vertigo.

You mean contradictory information I think.

Listen to the radio show, it puts and interesting slant on community representatives.

There has recently been a program about community spokespeople on the radio. https://www.bbc.co.uk/programmes/m001v3j4 They used to be known as busybodies.