> -1 degrees outside

-1F is -18C

-1C is 30F

They're from London, so it's the "not even cold but it's negative" rather than "actually cold and heat pumps aren't a good idea" measurement.

for those places where the scop is low, you have to drill for heat. If that's not possible then maybe a system where you can burn wood to suck the heat out of that.