In our previous house you knew only too well when it was frosty outside. This morning I blithely stepped out and was taken by surprise by the frozen pavements because this house really does seem to maintain its temperature pretty well. The weather the rehau doesn't like is wind and we're noticing that even if the internal temperature drops by 1 degree and forces the top-up heating to come on we are tending to use three times the amount of electricity we use on days when it doesn't start up. Hopefully that will sort itself out once the fabric of the house is warmed up(?).
In the meantime here's more proof that the insulation works with a picture of our roof, the only place the ice is melting is where the air is expelled from the vents on the 'chimney':
And the reason why we need a chimney should be obvious at this time of year.... though I hope the reindeer are sure-footed enough to cope with the roof angles.