The impact of reducing the flow temperature of a domestic gas condensing boiler was measured at whole-house level under controlled conditions at the University of Salford Energy House test facility.

The study found that:

• Lowering the boiler flow temperature reduced space heating gas use eg, lowering it from 80 degrees to 60 degrees saved 12% of gas used to heat the house
• However, it also slowed heat-up rates and lowered internal air temperatures e.g. when lowered from 80 degrees to 60 degrees, heat-up times in the morning went from 23 minutes to 37 minutes.
• The reductions in gas use measured are primarily due to increased boiler efficiencies rather than reductions in internal air temperature.