Does anyone know how much difference there is between the heat loss through single brick and double brick with cavity insulation?
I have double brick with cavity insulation, and my friend has single brick. When they come back from holiday, their house takes 48 hours to heat up from 5C to 20C. Mine takes a few hours! We both have a similar house with similar sized radiators, which all get piping hot, so I assume it's nothing to do with the boiler.
The only other thing I can think of is they have nothing behind the radiators to reflect the heat (silver foil?) - neither do I, but the double brick presumably helps here. I cannot understand where all the heat is going!
We both have similar loft insulation.