Retrofitting is becoming all the rage in London. This is the process of taking an existing building, adding new technology or features to its older systems, and making it more environmentally friendly by cutting carbon emissions and making it more fuel-efficient. 

Full retrofits can mean a reduction of 50 per cent to 75 per cent of carbon emissions and in some cases more.

Tom Pakenham is one of London's retrofitting pioneers. In 2010 he and a team of engineers, architects and builders undertook the epic conversion of his draughty, freezing cold, solid brick-walled Victorian house, which he lived in with his young family in west London, into a zero-carbon, energy-efficient home for the 21st century.

Amanda Burrell meets Tom to find out how it was done.