Mike

The advantage of moisture permeability is that, should any moisture get into the structure, it has an easy escape route - for example to reduce the risk of rot in timber windows. That's why I chose to use it on my current project - though I had to rip the cheap stuff out of the installers hands and give them the genuine product!

It's fine for sealing membranes to each other or to adjacent surfaces - I've used it myself - but I wouldn't use it to seal plywood joints. If you're sealing ply for airtightness then I'd use an airtightness tape. BTW it does set, but it will remain flexible - to a point - and tacky.

I'd go further and suggest that everyone should be required to vote. Reports of the benefits of doing so in Australia - such as this one from the BBC - seem, on balance, to be be positive. In particular, it means that any party that wants to get elected / stay in office has to address the concerns of all segments the population, rather than just the demographic that habitually votes.

+1. There are a lot of inferior competitors that perform much worse - it sounds like you may have one. No; it's very good but, as mentioned by @SimonD, even genuine Compriband has limits. I recall calculating that their window strip is good for wind up to around 70mph. In an exposed position, it would therefore be a good idea to have a second line of protection. Either something to shelter it from the wind - your timber cladding might be enough do that - or vertical & horizontal 'cavity trays' behind it. For airtightness, add Ilbruck FM330 form (or similar) and/or an airtightness tape internally. Sealant would block Compriband's moisture vapour permeability, so if that property was one reason for choosing Compriband you'd loose it. If that's not a concern, then a suitable mastic is OK.

Unless the developer did something stupid, the chances are that if it's been standing for a couple of hundred years, then you'd be unlucky if anything major happened in the next 7. And if it's minor, then it's not going to be quick & easy to get anything fixed under the warranty anyway. In short, it wouldn't worry me - but if you're not familiar with buildings & what to look for, think about getting a Structural Engineer's report.

+1. You need to identify the problem(s) and fix them. The IR thermometer should help to identify any gross air leaks that are in line-of-sight if you poke it through a down-lighter hole, but probably not not all of them due to the restricted vision. Yes, unfortunately this is likely to be necessary.

That poses an interesting question. It seems that it's actually France that has the higher heating requirement; the mean heating degree days (average figures for 2019-2024) are 2,080.81 for France and 1873.53 for the UK. That assumes that both datasets are population weighted - the UK certainly is and I'd be surprised if France wasn't - and also that the UK is still calculating as it did when it was an EU member.

A lot of that presumably due to the costs of the grid - a bigger country to connect, most of it away from the North Sea, and more rural areas too far away to connect (where main options are electricity, oil or propane).

Ignoring the saving on standing charges mentioned by @JohnMo - in fact ignoring standing charges all together - I just looked up the domestic rates here in France (first half of 2025, including tax): Electricity: €260/MWh Natural gas: €134 /MWh Ratio: 1.94 in favour of gas Compared to the UK (October to December 2025, North West region): Electricity: £271/MWh Natural gas: £63/MWh Ratio: 3.4 in favour of gas Which is undoubtedly a key factor in the popularity of heat pumps in France. Not to mention that gas has been banned for new developments for several years, and that replacement boilers (but not heat pumps) are hit with 20% VAT. It certainly looks that way.

It is indeed strange that you seem to be in a group of 1 with this one, but good to have your feedback and a resolution. It's unfortunate that it didn't go as expected.

It should either fall towards the unit, or towards to the wall vent - but you can also have some falling one way, the rest the other. So maybe you create a high point instead of a dip? It's only the exhaust that's susceptible to condensation, so don't worry about the intake duct.

I don't have roof vents, but yes, they need course mesh - see also this thread: You need to access them for maintenance, but that could be from inside (e.g. though a filer box) or outside. Wall vents are may be easier, but I guess you don't have that option.

You have an interesting building and some interesting challenges there! For the walls, consider lime-hemp (hempcrete), which can be applied directly to the wall in multiple layers, or cast against it using formwork. There are multiple examples of both on the internet, at least in French. Hemp handles moisture vapour very well, though not liquid liquid water, so you would need to make an assessment on the suitability and thickness. Your self-made insulating lime mortar sounds an interesting alternative. If you have lots of damp below the floor, you might want to consider laying ventilation pipes within the glass aggregate, connected to an extractor fan. If you search for hérisson ventilé you will find some examples. This may be enough to make the walls suitable for the hempcrete, if you think that it may be otherwise too damp. If the walls are still too damp for hemp, then your idea of expanded cork sheets sounds good, since cork won't be affected by moisture. I've used it myself in small areas - mainly on my chimney breasts - fixed with lime-based Isovit e-cork. You haven't mentioned how you are ventilating the building. I would suggesting using some form of continuous mechanical ventilation - dMEV / MEV / MVHR - to help control the internal relative humidity.

Not yet! Why not get some smoke pellets & test it yourself? Take a video of of any problems. And disable your smoke detectors...

Yes, that's the same 3m3/m2.h (and the same Lowe who first came up with the figure in 2000); it crops up in many places. The conclusion to that paper is interesting (though I know that it too has received some criticism): This paper has shown that previous analyses indicating that MVHR systems should only be installed in properties with an air permeability of 3 m³/m².hour @50Pa or less are based on outdated information and flawed assumptions using a modelling system which was never intended to be used to compare ventilation systems. A modern MVHR system will result in significantly lower CO2 emissions at any reasonable level of air permeability. However, an MVHR system’s primary function is ventilation and, in this capacity, it is far more effective at providing a good quality indoor air environment – regardless of external conditions – than natural ventilation. There is no clear up-to-date evidence behind the rule of thumb that says MVHR is inappropriate for dwellings with air permeability above 3m³/m².hour @50Pa. This analysis has shown that MVHR systems result in improved ventilation and lower carbon emissions for all levels of airtightness. There is a compelling case for MVHR systems to be fitted in all new dwellings and to be strongly encouraged in retrofits where significant reductions in energy demand are being targeted. It does underline, though, that the 3m3/m2.h 'guideline' is far from universally accepted and that it shouldn't be taken as definitive when deciding whether or not to install MVHR. Particularly if there are other reasons why MVHR might be desirable - to filter the incoming air or avoid external noise infiltration, for example.