Don't work in old property
actually they will work fine but the heatloss calcs must be viable before work commences. I'm in process of extending and insulating an 120 year old solid wall house which will be having a heat pump. It has to be taken back to brick, all the floors broken up and windows chopped out, reveals insulated etc. None of this is remotely possible if its habited during the works and its probably only another 20% to knock it down and start again. Obviously our amazing planning system would make this hard.
After insulating and making air tight it will be peanuts to heat. £1 of electric buys £3 of heat at a minimum, the latest heatpumps are closer to £5.
It's a step change for the building industry, no more RSJ lintels, no more 7n conc blocks below damp, massive attention to detail for preventing cold bridges, air leaks. All totally impracticable of course as these isn't a training course you can go on that teaches it all.
So for legoland builds they will be built same as always with minor tweaks and then heat pumps forced to run hard to make up for poor quality of workmanship and people will moan about the costs of running them.
On the plus side you will get lots of free condensation/black mould on every cold bridge to enjoy. Air tight houses cant dry out without mechanical intervention.
It's all cart before the horse.