Loft insulation

Walking down the street today, I noticed that ours was the only house with frost
still on the roof. The reason is simple, we have loft insulation both on the
floor of the loft and also inside the rafters. It makes an enormous difference
and wasn't even that expensive to do. People tend to go for the expensive
visible things like double-glazing and fail to realise how much money goes
straight through the roof. If you've only got a thin layer (3 or 4 inches) of
loft insulation, then you could almost certainly make the house warmer by adding
extra.

I also find I gain a lot by passive solar heating. When it's cold, like today,
I open the curtains on the sunny side of the house and close them on the other.
That can warm rooms up very nicely, esepcially if I close the curtains the
minute the sun goes down. It's free heat.