Mike

Welcome to the forum! If the loft is the only place it will fit, then installing it within an insulated but unheated enclosure is good. Your loft access trap also needs to be big enough to get it through, and you'll need good access for filter changes & other maintenance. And, although good MVHR units don't make much noise, I'd not put it directly over a bedroom if there was an easy alternative. If it will fit within the heated envelope - utility room, kitchen or elsewhere - then that would be preferable. No need for a heating loop unless you're planning to use it to feed a duct post-heater to top-up the air supply temperature. That's not often done except when the MVHR is used as the main source of heating in Passivehaus. BTW, if you've not already picked it up, add airtightness to your to-do list. It's likely to be the most cost-effective improvement you can make & it plays a major role in protecting the fabric of the building from potential moisture damage.

It probably depends on the business type :) Micro-Entreprise, Entreprise Individuelle, SARL (Société à Responsabilité Limitée), EURL (Entreprise Unipersonnelle à Responsabilité Limitée), SAS (Société par Actions Simplifiée), SASU (Société par Actions Simplifiée Unipersonnelle), SA (Société Anonyme), SNC (Société en Nom Collectif), SCS (Société en Commandite simple), SCI (Société Civile Immobilière), SCP (Société Civile Professionnelle), SCM (Société Civile de Moyen).

You appear to want to do the left illustration below. I'm suggesting the one on the right. But maybe you're trying to do something else.

Why not use a 600mm riser before it?

2250 certified PH homes. They claim 8,000 (in >300 development projects) under construction, compared 193,010 new homes built in the UK in 2023. If you look deeper, 6,400 of those are being built by social landlords, who benefit from economies of scale and take a long-term financial perspective in their investments, so around 1% doesn't seem entirely improbable, even if 'under development' doesn't = due to be completed this year.

Passive Houses now makes up around 1% of UK new builds, with 10's of thousands certified world-wide and >30 years of experience...

It's a future project, but this approach (probably the one you found) looked promising: Zehnder ComfoAir CA350 integration

Not yet. I also plan to get mine hooked up to Home Assistant in due course.

The standard requires <0.6 ACH @ 50 Pa, but not because it's hard. When they build the first Passive Houses they found it easy, with proper care & attention, to achieve 0.2 to 0.3 ACH, so reasoned that 0.6 was a readily achievable goal.

+1. If built to PH standard, then you won't need much heat nor a conventional heating system, but adding UFCH loops costs little. Add a Willis heater and you've got a cheap heating system, or a heat pump for heating and cooling. You're not alone. When they built the first 4 experimental Passive Houses they didn't believe it would be possible either, so they installed radiators. They were rarely used - after 2 years of temperature stabilisation heat demand averaged <10 kWh/(m²a), except for 1996//97 when it was 1 kWh/(m²a) extra. Last year the original gas boiler was replaced, after 34 years, with a communal 8 kW heat pump, providing hot water & space heating to all 4 homes. From memory I think they are all about 150m² floor area.

The neutrals & earths are there, but indicated rather than individually drawn: I don't think RCBOs would make it more busy (they would take the place of the breakers, marked D2.1, D2.2, etc.), but there would be some differences. A UK build using rings would normally be have fewer circuits, but with more on each. Radials are required in France and the number of outlets / points / devices per circuit is also limited limited - for example power circuits are limited to 6 / 8 / 12 outlets (where a double outlet counts as 2, not 1), depending on location and whether 1.5 or 2.5mm² wire is used. So, barring late changes, I'll have 28 circuits.

Only if open pipe 'gravity hot' and then cold mains the other side Must be the French rules clouding my memory :)

My understanding is the same as @JohnMo's - when mixing hot & cold you need single check valve. Regular cisterns have an air gap between the water inlet valve & the water level, which is fine. Double check valves for outside taps. Washing machines & dishwashers are required to have built-in valves, but nothing to stop you adding another.

Out of interest, in addition to the architectural electrical drawings mentioned above, in France you also need schematic electrical drawings. They're normally drawn by the electrical contractor as part of their contract. Without it the Electrical Inspectorate won't test the installation and, without their certificate, you don't get a mains connection. It's also used for subsequent maintenance. Example below for 1 row of my consumer unit (still in draft, which is why there's a duplicate D2.1):

It's true that buildings without a DPC rely on moisture evaporating from the wall. However some height difference is needed between external ground level and internal floor level, so that enough moisture has evaporated before it reaches that floor level. If the floor is timber, then you also need ventilation beneath the floor, from one side to the other, to prevent excessive moisture build-up. If there's now a concrete floor with a DPM, that will block the evaporation towards the inside - in which case, unless the wall can evaporate the extra moisture to the outside, it's likely to cause problems on the inside above floor level, making that height difference even more important. In other words, sandstone can only deal it in the right conditions. So definitely a good idea to do some remedial works as suggested above.