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So, yet further heat-pump adventures. Last week, a technician visited - he seemed very reasonable. Unfortunately, we just got the same answer that we got a little earlier from another installer: his company will not install the external unit on the shared courtyard, to avoid liability due to noise. We could try to find yet another installer (as the company suggests) but we are already seeing a pattern here. It may be wise to reexamine our choices. We can't of course have a setup where input air and output air mix indoors - that's what the architect had in mind in October and November, but that is madness (as became clear as soon as I got precise information from her and I posted it here). The question is then whether we can have a setup where the heat-pump takes air directly from the exterior, and outputs colder air (in winter) to the interior. It seems wisest from many points of view to do this in the (small) garage (which is gradually becoming a bike shed/ex-garage, anyhow), which faces the street, rather than in some sort of closet facing the courtyard, as in the doomed October-November plan. It would be something more or less like this (from her old plans): Now, the version of the plan here shows an Amzair Monobloc (https://www.amzair.eu/nos-pompes-a-chaleur/pompe-a-chaleur-optim_duo-2/) which is not ideal from several perspectives (very expensive, COP not among the best, not among the quietest heat pumps - since the garage faces the street, that's no longer a concern for the neighbors, but it may be a concern for me, since my main room (library/piano room/...) sits right above the garage). The fact that it is a monobloc is also no advantage - it might make hooking it up to the VMI more complicated (should consult the architect again on that one). One alternative is to have a split heat-pump, and have the "outside" element attached to the opening of the garage, much as the above. That is possible, and in fact there is a (most likely overpriced) kit in the market for doing so: https://www.atlantic.fr/Chauffer-le-logement/Pompe-a-chaleur/Aerothermie/Aerothermie-Air-Eau/Wall-In As it says, it works up to 8kW, but that should be more than enough - the spreadsheet gives me a total heat loss of 5.3kW at outside temperature = -2C. Questions: (a) Should this work well? The input would come directly from the street (presumably as high up from the ground as possible), the output would go into the garage (which would presumably have to have a ventilation grille further down to allow cold air to come out, even though that's not shown on the website; in fact I'm having a hard time seeing where the air goes out of the box). The garage would presumably be very cold, so we would have to insulate the garage well (heat and sound), on the ceiling and on the "upper" and "left" walls of the garage on the plan (my laundry and the medical cabinet next door, respectively). Is performance likely to be affected? (b) This is a proprietary system fitted to work with the company's (Atlantic) own products. The technical specifications for the Alfea Extensa 8 R32 do not seem bad (https://idealheating.com/new-build/products/alfea-extensa-a-i-r32), though they do not seem to indicate how much indoors noise the unit produces when fitted in with the proprietary system. (I'd have to see as the total cost - notice it does not come with a hot water tank). At the same time, it would seem logical that there should be products that work with other heat pumps, including ones that are particularly quiet (Saunier-Duval aka Vaillant, for instance, or Mitsubishi Zubadan). Are there any? Thoughts?

Another chapter in the renovation saga! (As some people know, we are carrying out a major renovation of a duplex near Paris dating from 1930. Proper cellulose and reflective insulation everywhere, new radiators adapted to low-temperature heating (keeping some of the old ones), ... We already cut off the gas, and are trying to choose an air-water heat pump. We've bought a broken-down courtyard outhouse from the coop so that we can put the "outside" part inside and not bother the neighbors.) We are now inclined towards the Hitachi Yutaki S 2.0 heat-pump, as opposed to the Amzair Optim'Duo, mainly because the company that was going to sell us the Amzair dropped the ball and didn't get back to us with a precise quote. (There's also the fact that the parameters for the Yutaki are somewhat better. It also looked originally as if it was going to be a lot cheaper, but given how much the installer wants to charge us for this and that, I am not sure that this is still true.) Now, the website for the Hitachi Yutaki 2.0 emphatically states that it can also be run backwards, for cooling in the summer. How would that work for an air-to-water heat-pump? Is that only for people who have underfloor heating (I am not one of them)? Or can the heat-pump really cool water (up to what temperature? not clear from the documentation!) that can be simply circulated around the radiators just as one circulates hot water? What measures do I have to take in practice?