| Nothing convenient. Bits and pieces here and there, tons of forums, a few videos, a bunch of books, a few specialists who gave good advice. The inbound temperature into the radiator network took a dive from about 70°C to about 40°C here (I _could_ push the inbound temp to nearly 50°C but by then I'm no better off than with resistive heating), and that's rather obvious when heating the rooms. The main advice everything came down to was "have a lot of surface that can heat" and from my experience that seems to be quite true. The house has a bunch of radiators that never ran in the nat-gas days, basically it was overcommitted on heating surface. Now they're pretty well used. Another retrofit option that I had in the back of my head was radiators equipped with a fan to move the air along the radiator surface more quickly (essentially creating "virtual heating surface"), but I didn't need those. Other than that, warm and cold parts of the house (e.g. basement) are more clearly separated. A FLIR camera module for my phone gave some hints on where heat escapes so that I could focus on the right spots. When a larger rework of a room is due (and there's a huge mess in any case), that's a chance to look into floor or wall heating there, connected to the same system. Once that's (mostly) done, I suppose the inbound temperature can be reduced some more, and I expect super-linear electricity savings from that (due to the way the heat pump works). In terms of costs, it comes out at about the same, although there are more options in electricity availability, and I suspect that pricing there remains more stable than with fossil fuels, so longer-term I expect operating costs to develop beneficially (even if that only means "remains flat"). TCO of the project, I don't know, but I was optimizing for long-term OpEx for various reasons. By the way: Heating engineers tended to dismiss the project, but the project started before there were any issues with gas supply, so "just use gas" was their go-to solution anyway (for the eco-conscious, they dangled the carrot of "it's H2 ready!", even though it's unlikely that the pipe work will ever support that). Not sure if the attitude of heating engineers changed in the meantime. In the end it was done by air conditioning technicians, and it can be switched between heating mode using radiators and AC with split system frontends, so this house covers cold winters and hot summers with just one external device (which pleases the historical landmark office) |