As well as building a windmill in the dark days of the 70's, my Dad also built a solar heating system for our first swimming pool in 1976.
He had been inspired by a television programme called I think House of the Future, does anyone remember it, or know if it is still standing? They built a house that was at the time the ultimate in energy saving technology.
By the way, outdoor pools in Lancashire, even solar heated ones= bad idea, we have an indoor one now.
