It doesn't take Mr Tibble very long to find the source: "A lot of the heat down here is not just from the boiler, I would say 60-70% of the heat is from this, " he says, pointing at unclad pipes carrying hot water from the boiler.

BBC: NEWS | Science/Nature | Taking the heat out of energy costs

If you are living on means tested benefits AND you live in the hardest-to-heat homes you may be eligible for a free new central heating boiler, insulation for a hot water cylinder, loft, cavity wall and solid wall insulation, draught proofing for doors and windows or renewable energy technologies such as solar panels.

BBC: Battling bills - what help is there?

The 59-acre (24 hectare) site will also boast a solar thermal hot water system to pre-heat the water for the heating system, and a biomass boiler that will provide heat using locally-sourced wood chips.

BBC: Bristol and Bath Science Park gets new solar roof panels