When geeks turn Green: Performance tune your energy bills

Does it work?

We've roughly halved our gas for heating per degree day and for hot water, so our gas consumption is down from about 9MWh per year in 2006-2007 to well under 6MWh in 2010 (remembering the exceptionally harsh winter that that was). A typical household uses 18MWh/y of gas for central heating and hot water.

Our electricity in the same time frame is down from about 10MWh per year (10,000 'units') to about 1.5MWh in 2010, and actually paying for importing about 1MWh (ie 1/10th of where we started) after the 'free' electricity from our roof.

So we've gone from spewing the equivalent of 6 tonnes per year of CO₂ to heat and light this house down to zero, while adding two small children to the household.

Look at our consumption, falling each year even as the winters have been more harsh:

Energy consumption chart (kWh/week) over recent years courtesy of imeasure.org.uk. Above: Three years' energy use.
Below: four years' energy use.

But meters are not the only fruit. I also did two rounds of thermal imaging: one myself with a borrowed camera, and one by a grown-up with his own, which helped me spot (among others) problems with our loft insulation and icy draughts where the bottom of of new front door wasn't sealing properly (taking all of five minutes to fix). Also when I had the energy performance certificate done I had the house checked for air leaks ("air pressure testing") and found that most of our unplanned ventilation (wasted heat and cold draughts) was from a supposedly-sealed old boiler flue from the kitchen; again the work of a few minutes for me to fix as it turned out.

Thermal image showing an otherwise undetectable
gap in loft insulation above an upstairs bedroom...

...and a slipped catch at the front door preventing the
seal from working properly, leaking in icy air.

You need to try all the tools in the box to see what works!

So, as a geeky optimiser of performance, am I done yet?

Hell no, there's carbon-negative in my sights next!

Part-way into this tweaking and tuning I'd managed to get a band B Energy Performance Certificate (EPC) such as you need before a sale: I'm aiming for band A next time and a higher selling price as and when we move.

I've insulated another room-and-a-bit with aerogel this autumn, in fact, and I am working on some other goodies: stay tuned! ®

References

• http://www.earth.org.uk/saving-electricity.html Saving Electricity (and Gas): some of the gruesome details and monthly metering and tracking
• http://www.earth.org.uk/thermal-imaging-survey-of-house.html Thermal Imaging Surveys on our house
• http://www.earth.org.uk/testing-a-house-for-air-leaks.html Air-leak hunting
• http://www.degreedays.net/ Custom Degree Day Data
• http://www.imeasure.org.uk/ An online tool to help you accurately monitor your home energy use and carbon emissions