Early 20th Century Semi-Detached House

CONSTRUCTION: Typical small early twentieth century solid-wall house.

KEY FEATURES: internal and external insulation, solar pv, wooden double and triple glazing, solar gain conservatory, and LED lighting.

Wanting to make some significant alternations to the house, the owners decided that this was a good opportunity to think holistically about how to make it more energy efficient – thus both reducing bills and helping the environment by using less fossil fuels and generating their own electricity.


    Before After
Energy Rating 43 86
Actual Gas consumption p.a. 11,613 kWh 6,903 kWh
Electricity generation p.a. 0 1,500 kWh
Carbon emissions p.a. 5.5 tonnes p.a. 1.1 tonnes


Energy Performance Certificate

A before and after EPC showed that the improvements had doubled the energy rating from 43 (E ) to 86 (B).           The table below shows the effect of each improvement incrementally:

Improvement Rating after improvement
Seal open chimney 44
Wall insulation 59
Draught proofing to doors 60
Double/triple glazing 64
Bathroom ceiling insulation 66
Disconnect decorative gas fire 72
Solar PV 86



“Our back door was very draughty. This and the uninsulated solid walls meant that in winter, the boiler used to be on most of the time, struggling to reach the temperature on the room thermostat. Now the heating comes on for an hour or so, and the temperature is reached so the boiler goes off. Having a well-insulated house means it keeps the heat in for longer, so the boiler is on much less, and we have noticed the difference in our gas bills.”

Open case study as PDF

 For additional information about the impact of each of the improvements for this case study, click on the individual “related opportunities”