Mike

You're right not to get it - it's no different to any other underfloor heating. This has come up before:

As mentioned in another thread, text from a PassivHaus MVHR certificate says that 'In case the unit’s moisture recovery rate is larger than 60 % its airflow rate must be controlled based on the indoor air humidity, in order to prevent temporarily elevated humidity levels.' So yes, it seems that there is a potential for excess humidity in some circumstances so, to avoid problems, the unit needs to automatically switch to boot mode if humidity gets too high. If it's not doing that, I guess that there are at least 3 possibilities: it could be there's a control problem; maybe it requires (an additional / replacement) humidity sensor(s); maybe some of the exhaust air is finding its way back into the supply. +1

Yes, on the intake it'd definately easier to have one that doesn't need extra insulation. Mine was from Econology in France (site temporarily down). InovaTech in Germany sell a smaller one. So too does HomEvap, sold here in the Netherlands.

My Zehnder intake is around 10mm too - enough to stop leaves, bats & birds. I then have a filter box before the MVHR unit, with a large filter that can easily be changed, before the MVHR filter takes out anything that remains.

The deterioration of a fixed battery must have a negative impact on resale value; the economics of battery swapping might work if that is taken into account. Standardization would certainly help. The EU already has a directive (2023/1542) require that "batteries, as well as individual battery cells included in the battery pack, are readily removable and replaceable by an independent professional at any time during the lifetime of the product", so it wouldn't be a huge step to go further and specify standard battery pack sizes. A quick search also shows that the European Committee for Standardization is already drafting "Technical specifications for swappable battery system applied to L-category vehicles"

Or get a car where you can swap the batteries about as quickly as filling one with fuel, when they reach the UK: https://www.youtube.com/watch?v=WOsy_EvtHr4

I'd be with you for at least the fade-up feature, given a suitable controller to automate it. I hate dark days too, so if the alternative was a fixed CCT of 3,000 K or less, then this would be useful. However, with my personal preference for 4,000K I never have a desire to close the curtains before dusk. I can see the utility of this for some people. Though, as a night-owl, it wouldn't suit me at all, at least not until the last few minutes of the day. In short, I think that the value of changeable CCT lighting depends on how you like your lighting; I'm not a fan of cool lighting (except in limited circumstances) nor of warm lighting (unless it's in an old cottage or the result of real candles), but if you are, then go for it - in which case I'd recommend applying it to all lighting (that will be switched on together) so that you don't end up with an odd mix of colour temperatures.

I've used magnetic catches myself. Works well.

In addition to the above, lime is also strongly alkaline, which inhibits growth of mold & fungi.

That advice is for ceiling-mounted Coanda Effect vents; on a vertical surface things are different. Wall-mounted Coanda Effect vents are useful in large room used to direct air a long way across the ceiling of large rooms - but you don't what them in the position illustrated as that air will be directed down the ceiling & the wall. I'd be looking for a regular (not a Coanda Effect) vent, preferably with adjustable fins that give you the ability to direct the air flow. However check that you have enough space for a vent as drawn; it may be necessary to cut a hole through the RSJ for the duct (which would need to be part of the Structural Engineer's design) or to enlarge the boxing - or switch to a Coanda Effect vent on the horizontal part of the ceiling (probably the easiest option). From £1,651 +VAT at https://phstore.co.uk/zehnder-comfoair-160/ (20% cheaper than BCP - you may be able to negotiate it down further). Of course there are various other brands. For example those at https://database.passivehouse.com/en/components/list/ventilation_small which are independently tested to more accurate standards than normal (where a higher efficiency ratio = better economy).

My apartment isn't so different in volume, so overall no worries in principle. Ultimately it's about how much fresh air you need per person in a room. For example, at 'normal' fan speed a double bedroom requires from 15 m³ / person / hr; in a room measuring 3 x 4 x 2.5 that's 1 ach (air change / hour), but double the size of the room and that drops to 0.5 ach. Low fan speed is typically 40% below normal speed, so those figures become 0.6 & 0.3 ach. In short, in a smaller home the minimum acceptable ach will be higher than in a larger home. Probably not. I don't intend to be running mine lower than 0.33 ach; in your case that would translate to a little over 50m³/hr. The exception might be during an extended absence, but at least some controllers (including my Zehnder) allow a schedule to be set so that the average daily airflow could be cut well back by having it run for only certain hours per day; that's not recommended except for longer term absence. I have the Zehnder CA225 (similar to the CA220 that's sold in the UK) - 60 to 150 m³/hr according to the PH certificate & 50 to 200 according to Zehnder. That's partly because I also wanted to sling it from the ceiling where I have some more space. That doesn't seem unreasonable if you plan to use semi-flexible ducting, to keep the airspeed (and hence the noise risk) low. You could experiment using my MVHR calculator. It wouldn't be my first choice; I'd probably make that shower tray shorter to create a cupboard off the corridor. But in an enclosure with good sound insulation & anti-vibration mounts it should be OK in principle... Choose ceiling mounted Coanda Effect vents - Zehnder Luna, for example - and there should be no problem; keep them away from the walls by at least 350mm (750mm better, centre of room ideal subject to light fittings taking precedence).

+1 to plastering but, in case it's not obvious, done after first sealing the junctions with other materials & components

Not answering your question, but why would the alucald ones need replacing after only 9 years?

That's an interesting proposition and an attractive price. I wouldn't recommend it to someone unfamiliar to the industry though, not unless they're confident taking on the contracting + payment + variation processes by themselves, or unless their architect is going to get involved in them.

That's an unusual octagonal access hatch...