I have a very large very old & complicated listed stone property (was two houses, one farmhouse from the 1600’s, one a bit newer, both joined together in 1830’s and extended to “Georgianise” the front to be trendy for the time). Three stories, 4 staircases, loft insulated to 30″ where it was reachable (old servant qtrs in loft space over 1/2 of the property ) otherwise, no insulation, just lathe and plaster air gapped to 36″+ of sandstone. Mix of sash and case windows (old ones are solid oak, newer ones usual crappy wood) and double glazing (at rear – fitted just before the building was listed). 9 double glazed conservation area approved skylights (replaced those crappy metal ones that leaked heat like sieves).
We have 15 radiators heating all but two of the rooms – they are heated when used by electric fan heating. The gas boiler does ok down to low negatives, after that it loses ground, so at -1 we can maintain 20 deg, at -6 we maintain about 16 deg etc. We switch it off overnight, so, after the heating being on for 2 hours this morning, at -1 outside my study was 15 deg. Now, after heating on for 4+ hours & lined thermal curtain closed over the huge Georgian single pane window, its at 18.6deg.
Not complaining, we knew it would be a pain to heat, it really needs a decent woodburner. Had a heat pump/alternative fuel guy round a few years ago, basically told us it was a waste of time, the system would need to be so big it would cost a bomb to install and to run & like others our pipework for the radiators is too small already, so it would all need ripped up. The furthest radiator from the boiler is approx. 60ft away, so there are some epic pipe runs under our main hallway flooring.
In life, it's not who you know that's important, it's how your wife found out.