A series by BEG volunteer Matt Wood. Matt works as an energy consultant for housing retrofit initiative Energiesprong and is also a member of the Bristol Advisory Committee on Climate Change.

4: CHEESE

In this series, I’m going to explain how I’ve made my house zero carbon and how you can too. In the previous blog I talked about solar panels. Today we’re talking about thermal imaging and smart metering.

For those who looked at the data table in the previous blog, you’ll see the last year I recorded was 2013. I didn’t do anything for several years because I moved to London for a job, but when I came back, I carried on with my plan.

I knew that I would need to extend my mortgage to do what I wanted, so until that was possible I could only do relatively low-cost things. I replaced my patio doors that were broken and repaired the hinges on the double glazing which were not closing properly and creating draughts. Unfortunately the inverter on my PV system – which converts DC electricity from the panels to AC for use in the house and to export to the grid – broke after just 5.5 years (6 months after the warranty ran out!); you would usually expect one to last for 10 years. Luckily they’re not too expensive and the new one has a 10-year warranty.

Step 3(a): In 2018 I got a CHEESE survey. This is a simple thermal imaging survey which helps you to identify draughts and cold spots. The left picture below shows the cold spots around the top of the bathroom tiles and window. This was relatively cheap and easy to fix with some draughtproofing strips and some retiling. The right picture shows where the insulation around the loft hatch is not a good fit. This can be fixed by replacing the loft hatch with a plastic one (something I haven’t done yet but isn’t very expensive).

My actions after the survey:

• Retiled bathroom to reduce cold spots near the ceiling

• Filled cracks and holes around window sills

• Got the patio door company to come out and adjust hinges which had sagged, causing a draught

• Replaced more window hinges which were causing draughts

• Plan to replace loft hatch

Step 3(b): One of the most important things for me is to understand my energy usage better. I’ve been taking weekly and monthly meter readings since I moved into the house, but what I really wanted was the half-hourly meter readings that a smart meter gives you. In 2019 I got my supplier to install smart meters for gas and electricity. I had to badger them a bit to give me the actual data, but they did so in the end (and continue to do so).

However, if you have solar panels, the electricity smart meter doesn’t actually monitor whether you’re using electricity from your solar panels or imported from the grid. The solar panel meter is a “dumb” meter. So I also had a separate meter installed which can monitor import, export and generation. This cost around £500 for the meter and installation, so I wouldn’t recommend it for everyone, but for a data nerd like me it was essential.

I now know that the solar panels provide about 1/3 of my electricity and I export about 80% of what is generated. These figures may have varied over previous years but I don’t think by much. So although I can say my house is (almost) zero carbon, it’s mainly because I’m a renewable energy exporter. You’ll also notice that in 2012 and 2013 the carbon footprint was negative, but it’s since crept up. This is partly due to a couple of colder winters, but also because the national grid has reduced its carbon intensity by around 50% since 2010. This means the amount of carbon I “offset” by exporting renewable energy to the grid has gone down, yet the carbon intensity of the gas I burn has stayed more or less the same. One more reason to get rid of gas.

Next time: The big one!