Mike

BT are having a laugh. On the plus side, the InspirAIR Top 450 Premium ERV is on the Passivhaus database, so there's absolutely no justification for the 30% heat recovery claim, and no reason to doubt that you'd be in the 80% zone. But €7,315 including VAT? You could buy one here for €3,464. If they've quoted list price for everything, no wonder the total is crazy. Barring unusual circumstances, you also don't need the ERV version. ERV = enthalpy heat exchanger, which retains the moisture in the building. That's rarely chosen and may be a poor choice if you're expecting the MVHR to keep the structure free from excess moisture. They also cost more than a regular version; €1K more on the Aldes list price. €8K for the other quote isn't cheap, but it is harder work retrofitting. If they've priced for the same MVHR unit, you should be able to negotiate down to the non-ERV version. On the other hand, if you have room to add a big filter-box on the main air intake, I'd do that to save having to change filters to often.

Cork is in a separate category - it's got an exceptionally strong set of characteristics, and for wet conditions it's the only option. However the price is much higher than the others and it's not compressible, so it can't be squished between rafters / other obstructions. I have used some on my current project, but mainly fixed to the faces of the chimneys, hidden behind plasterboard. For hemp / flax / wood fibre, there's not a great deal to choose between them. From memory, wood fibre is fractionally ahead in terms of insulation, but one brand / product nudged ahead for winter insulation, and another for decrement delay in summer. Hemp & flax just top wood fibre for moisture buffering and, as that's my top concern, it was a leading factor in choosing Biofib. The exceptional physical flexibility & compressiblity of the Trio was also a big plus in adapting to uneven surfaces, so using one layer of Chanvre + 1 of Trio seemed optimum.

Yes and no. France was into centralised ventilation decades ago, and it seems that quite a few manufacturers added cheap heat recovery units to their line-up (much like extractor fan manufacturers have in the UK) - and the performance of many probably isn't very spectacular, so may deserve a poor reputation. It's also true that the figures reported by most manufacturers over-state reality, thanks to the ill-conceived tests that that are used. The exception are MVHR units listed in the Passivhaus database, which can be relied on. They've been independently tested to realistic standards, rather than those used by manufacturers: https://database.passivehouse.com/en/components/list/ventilation_small. The 'Efficiency Ratio' (which takes into account electricity used as well as heat recovered) is the key figure for comparison. For example, the near-identical Zehnder ComfoAir 200 & 225 models both have a heat recovery rate of 92%, but the 225 has more efficient fans so has a higher Efficiency Ratio (0.69, rather than 0.67). It would help reflect the heat back :) Note, though, that the larger part of the SMIC cost isn't the actual painting, it's the preparation with 2 coats of 'skim'. Except in France they use something more like filler, which isn't anything like as good as the gypsum skim used in the UK, but is still better than regular jointed plasterboard (though not €3.5K better). Still toying with the idea of importing some gypsum board finish from Italy for mine; so far I've only bought 1 bag to test... It could indeed, provided you buy the right grade - there are some really interesting decorative ones around too: https://www.liege24.fr/shop/80-liege-mural-3d/ It would be likely to get accumulate some damage from knocks, but it is easily repaired. Not sure about that - you'd need to compare with the online tool I mentioned in one of your other recent posts. However the density and structure of a material affects the frequencies that are reduced, so in principle having two different materials could be useful in reducing the overall sound spectrum. Not not sure how much difference you'd hear in practice at the likely thicknesses, but it was a secondary factor in choosing to mix Chavre & Trio in my mansard.

Based on your constraints, I think that the (insulation) spec is about as good as you'll get. I'm not too shocked by the price either. A few observations: If you're still planning to install MVHR, you can very probably drop the vapour barrier from the spec; the MVHR unit is very likely to keep the moisture below problematic levels. Having said that, it may be difficult to convince the contractor to omit it, as it is required by the French DTU. And ideally you'd want a WUFI analysis to prove it (and obtaining the data for that could be tricky - I may have some next year). However, unless you already have one, I'd add back in an airtight membrane on the outer face of the insulation. That will be fiddly, so will cost more than the vapour barrier would have done (unless you DIY it) Think about a double layer of plasterboard, or at least upgrading the plasterboard to a high-density version, as it will be very exposed to knocks in your situation, and the extra layer will help somewhat with sound insulation. FWIW, my mansard spec isn't too dissimilar : Mento used as an airtight barrier + 100mm Biofib Chanvre + 45mm Biofib Trio + 2 layers of Gypso Omnia (aka Gypso Lignum).

Apart from considering the points above, yes, in principle you can put ducts through chimney stacks. However: The intake and exhaust terminals need to be separated by at least 1m horizontally, so you'd either need a large chimney, or two chimneys of similar height and exposure The intake would also need to be well away from any chimney that's still being used (or that might be reactivated as a chimney in the future), to avoid the obvious health risks

Quite likely a Testo 417.

I've not seen it, but I do recall reading that it's possible to break up the insulation within a cavity wall and extract it. Maybe using a robot rodent + vacuum cleaner, or something. You'd need to track down a specialist company.

Yes, recently-build German homes are underperforming by between 15 to 35% compared to their expected energy performance because of that! Its a major factor preventing Berlin (and Germany) from achieving its energy efficiency targets: Germany’s inefficient love affair with open windows - Politico Seems like they need to keep their windows shut more often (or use Stoßlüften) and lean to love MVHR

It looks in good condition & you have 200 years of evidence that it's adequate. What has changed over the years is that current standards require the timber to flex (sag) much less under load than would have been acceptable in the past; that's normally more a risk of cracks along plasterboard joints, rather than one of structural stability. I doubt the the BCO will raise it as an issue, but if they do, then you'll need that SE. If I were drawing the plans they'd just have a note saying something like "existing lath & plaster removed & replaced with plasterboard". And something similar if you're planning to replace the tiles externally / add additional insulation, etc.

No, it's never a problem that I've come across when the timbers are in good order. If everything had to comply with the latest Regs then you'd be demolishing the lot! It just needs to be safe and, if there's any doubt about that, then you'd need a Structural Engineer's involvement.

Wall ties are supposed to slope gently towards the outer leaf...

No, but you may be able to do it. The use of lime lies outside the current British Standards, so it would be down to your structural engineer to make an assessment of suitability. However the NHBC Foundation have produced a paper on the subject, which may help - The use of lime-based mortars in new build (https://www.nhbc.co.uk/binaries/content/assets/nhbc/foundation/the-use-of-lime-based-mortars-in-new-build.pdf) which does say that "The data available indicates that single skin brickwork or blockwork masonry constructed with lime-based mortars quickly develops sufficient resistance to vertical loads, but that it has less resistance to lateral loads at an early age and so consideration needs to be given to this at the design stage."

FWIW, I avoid using glassfibre now; it's not much fun to work with, even with a respirator & gloves.

I've used the 3M 6200 half mask for years - not sure if this is my 2nd or 3rd (the others wore out) - similar to the Dewalt one. I used a couple of other brands in the past, but ended up throwing them because their proprietary filters became unavailable. That's not been a problem with 3M. For dust, I use the 2135 filters; a pack of 10 pairs will last me for months or longer, depending on the dust levels.

From experience hemp is good to work with but really tough to cut - a toothed blade is impossible. If you're doing a small quantity, then you can get away with the Bacho Profcut PC-22-INS insulation saw, though it works works better with normal insulation (EPS, XPS, etc). For larger quantities of hemp or woodfibre, it's essential to invest in an electric saw with wavy-edged blades, which make it almost as easy as cutting butter. I only know of 2, but there must be others: Bosch Professional GFZ 16-35 AC + the TF350WM blades (I got through 2 pairs) - demo if you look for the video at https://www.bosch-professional.com/fr/fr/lame-de-scie-tandem-pro-fibre-insulation-tf350wm-3053403-ocs-ac/. Festool 577231 18V cordless You may pick one up on eBay, as I did.

You live in France. I don't remember them being that bad last time I visited the UK. Though it's been a long time since I made it to Cornwall...

Overall, remarkably accurate. Starting with all that 'clutter' in the fist section - all now available on your smartphone. They're partly right - you can recharge that smartphone wirelessly. Thankfully! And fashions have improved too.

At that thickness even the most expensive insulant won't do much; in fact it would be more-or-less decorative as it would be bypassed by the outer skin sitting on top of the beam (and maybe by the patio door). You may be able to build the brickwork off Armatherm (ask them), but if the brick is already in place there's no good solution. Other than to dismantle it it and approach it differently (and claim the cost back from the structural engineer who designed it?)

I've done similar, though using a plastic angle to keep them straight.

This will give you a clue: https://www.researchgate.net/figure/sopleths-for-growth-of-various-fungus-species-and-the-lowest-isopleth-for-mould-LIM-0_fig1_272886603

+1 for blown EPS. The silver / grey ones provide somewhat better insulation than the plain white.

If under a warm / hot shower I doubt MVHR on boost would give you any discomfort in an open room. There's scope for some consumer testing here - just don't post the photos :)

Zehnder's recommendation is that it should be close to, but not directly over, the shower. No reason given, but my guess is that it's not about the functioning of the MVHR unit, but rather that the air being drawn past the person showering could, in some circumstances, feel uncomfortably cool. For example if you don't have a good shower screen & door in place.

You'll still want to keep a healthy indoor air quality, so you'll need it running to ensure that the air stays fresh. And if there is condensation within the unit, the fresh air running through it is more likely to help to keep it free from mould compared to stagnant moist air in the unit if you switch it off. So I'd keep it running.

I'd like to fit 230V Tridonic LED light engines, pictured below, (as suggested some time ago by @Carrerahill https://forum.buildhub.org.uk/topic/13775-led-llmf/#comment-227778) in some plaster-in downlighters. The instructions for the downlighters show two different mounting options for the electrical connection. 1) Shove the connection block / transformer at least 20mm away from the lamp, which would work: 2) Mount the connection block on a stirrup (supplied), which doesn't work when using a light engine... ...if you've not already spotted the problem, the stirrup is fixed to the part of the downlight that's plastered into the ceiling. But a light engine needs wiring to the connection block; do that and you can't change it if it fails, unless you rip the fitting out of the ceiling. So option 1 seems the logical thing to do. However must be some regulations that require the use of the stirrup in some circumstances - otherwise, why supply them - but If there are, I can't find them, and the supplier can't tell me either. I only recall stirrups being used with GU10 (& maybe Gu5.3) lamps, so my guess is that it's a requirement for them. But as one of those could be retrofitted to replace my planned light engine, maybe that still needs to be taken into account. But then why show 2 mounting methods? Going round in circles... If anyone is able to, err, illuminate me with what regs apply and when, that would be very helpful.