You have to zoom in on the picture to get the full effect of it but this is one of the windows on the top floor when we opened the blind this morning. One of the bedrooms has got a duff blind at the moment and some heat still escaped through the triple glazing and the glass was clear. The blind on this window was down so no heat escaped and this is the pattern of frost outside to prove it.
And you know the best bit? We haven't had any heating on in the house for the past three days apart from a bit of additional heat in the sitting room because all the insulation has kept the temperature steady at 19°.
I know I shouldn't really be surprised this bit works ..... but I am!