Jeff V

Tagging on here, because we are in a similar situation. Our 50 year old warm air furnace finally died and the parts are no longer available. It could be welded, but it's time for a new system. There are two stage models available from the US - the air is first heated with heat from a heat pump then topped up with gas heating. It's not ideal in environmental terms, but it's better than all gas. To me, the biggest issue is that these are still gas units, and finding engineers to work on them is like finding hens with teeth. So I would very much prefer to divorce the heating from heat distribution, using something like a Johnson & Starley Aquair, but that doesn't allow for two stage heating without another separate unit. And then the controls are not OpenTherm based, so modulating the blower may be a problem. But this does allow sophisticated boilers to be used - so it may be possible to find a two stage boiler ... where water is first heated using the heat pump, then topped up with gas to reach 80C, which is the sort of temperature needed by the warm air. I'd also quite like automated registers/vents - like these https://smarterhomeguide.com/smart-vents/ - but that adds another layer of problem.

Hi. We've lived in our house for 20 years, but made minimal changes. It's a very non-standard, modernist house which had some very unsympathetic work done in the 1980's. We are hoping to be able to reverse much of that, and end up with something closer to what it was - replacing the PVC windows, stripping out the kitchen, and also making it much more themally efficient.