Is this Britain's most energy efficient house?
19 January 2014 Last updated at 00:38 GMT
A Victorian terraced house in Birmingham, typical of many houses in industrialised cities, could be Britain's most energy efficient house.
The 'zero carbon' house in Balsall Heath is lit largely by natural light, uses no fossil fuels and has no fuel bills.
Presenter Johny Pitts goes inside to meet its owner, architect John Christophers, to find out how he has made his house so energy efficient.
As well as saving on the bills, he also makes extra money by selling the surplus energy back to the generating company.
Inside Out is broadcast on Monday, 20 January at 19:30 GMT on BBC One West Midlands and for seven days thereafter on the iPlayer.