Pamela and Ian Wilkie live in a Grade 2 listed building at Hail Weston, in Cambridgeshire, which is the oldest house in the village. Because the home is very old (dated from 1535) it has no insulation apart from the roof and no cavity walls. The only part of the four-bedroom four-reception room property with proper insulation is a new wing. Also due to its listed status the house loses heat very easily. The couple wanted a more efficient way to heat their home, and as they explained: "Because we can't do anything to the house we wanted a system that didn't require modifying the home. For example, we aren't allowed double glazing as we can't do anything to the windows."