I am painfully doing up a late 1950‘s house. The construction is fairly standard New Zealand practice for the time, timber frame, weatherboard, concrete tile roof, 18mm tongue and groove flooring over a vented crawl-space and 10mm fibrous plaster walls and ceilings. The original construction of such houses was totally uninsulated and very drafty. (Although we have a temperate marine climate, New Zealand is no tropical South Seas paradise. We do get a few degrees of frost in winter and the whole place is horrendously windy all year around.) The ceiling and under the floor has subsequently been insulated, but unfortunately so poorly that I will have to redo them. I also have to come up with some way to heat the place economically, preferably using wood. Hydronic heating, with its ability to zone heat and use storage, seems ideal. I am not too happy with the whole idea of radiators or baseboards, which leaves radiant heat. The usual preference is to use under-floor heating but I have a few problems with that. Under-floor radiant heat requires that the floor be insulated. I discovered a disaster after I first bought the house, there had been a flood in the en-suite and the underfloor insulation, which was a sort of bubble-wrap aluminium foil stapled to the underside of the joists, had trapped quite a few gallons of water between the joints. No wonder the place felt a bit damp. As a result, I would prefer to insulate and condition the crawl space, rather than insulate under the floor. This is not so good for under-floor hydronics. Searching hearth.com, I came to this excellent connection of links compiled by Colin Morris. https://www.hearth.com/talk/threads/gasification-links-and-tom-reeds-research.11640/ One of Colin’s links was to a pdf on the www.heatinghelp.com site. The pdf contains a 160-page “Manual of Modern Hydronics”. It seems very good stuff. I had not ever considered the ceiling as a radiant panel but the manual points out that, since the heat mechanism it radiant, it doesn’t matter where you put the panels. Since wall panels are not very practical in my case, ceiling heating starts to look very appealing. The manual only shows one layout for ceiling heating. This is for pex-Al-pex in aluminium heat-transfer plates, that is only possible with a totally new ceiling. This would be very expensive and inconvenient. I wonder if it would be practical and effective to use the joist-space heating concept that the manual describes for under-floor use in the ceiling? This would have the pipes nail-clipped to the sides of the ceiling joists. A reflective layer would be stapled across the joints and normal ceiling insulation placed on top. If this can work, what water temperature is required? (The manual states that the temperature needs to be higher that if heat-transfer plates were used, but doesn’t say by how much.) Any Ideas?