William started his home energy efficiency journey by borrowing a thermal imaging camera from Cambridge Carbon Footprint’s loan scheme in 2022; he is now the Home Energy Officer at Cambridge Carbon Footprint.
After attending a talk by Rob Hopkins, co-founder of the Transition Network, on his then new book ‘From What Is To What If’ at the Cambridge Literary Festival, I started looking at my own carbon footprint and then looking at ways to improve the energy efficiency of our home.
We started with an analysis of:
Phase 1 set about improving the fabric: more loft insulation, draught-proofing, double-glazing and two new patio doors.
Phase 2 involved fitting solar PV panels and battery storage.
Phase 3 in the summer of 2026 involved more external shading and rainwater storage.
The aim was to:
The house is noticeably less draughty and feels warmer on cold, windy, winter nights.
As we had sealed the house as much as we could, we thought a MVHR system would be a good way to improve air quality and reduce the heat loss from having to regularly open windows or doors. We needed a patient and flexible installer willing to get all the ducting into our house in an invisible way, through cupboards and some boxed-in sections in our utility room.
Our chosen MVHR system:
Our installer, Jason, also services the system and replaces the filters annually.
This is the retrofit feature Fiona is most pleased with: for improved air quality and the Summer bypass air purge feature that you can run at the press of a single button to bring cold air into the house on hot stuffy nights. The vents are very discreet and completely silent in normal operation, and just audible during a purge. The price ~£12,000 seems reasonable.
Jason, from Temperature Management Group Ltd, took enormous care, discussed everything fully with us before doing any work and worked closely with Vent-Axia experts to specify and commission the system.
We are particularly happy with our new patio doors which are exceptionally well designed. The contractors who came over from Italy took exceptional care in designing the doors and did a great job coming back to fit them. The 17-week lead time was well worth the wait! At ~£7,500 a pair, they were not cheap, but they were beautifully made, with a very low u-value for very low heat loss. My review and picture of our doors are on their website at https://eterno-uk.com/excellent-reviews/
As we have a cedar shingle roof, we needed to use an in-roof system. The system fitted has:
It all works fully as expected. The Eddi diverter was not actually required, but the installers forgot to wire up the inverter’s auxiliary output, so the diverter was a work-around they included at no extra charge. We are very pleased with the 80% reduction in electricity bills – we should be in profit in ~10 years!
However, we are not so pleased that I have been unable to programme the SunSynk inverter (using my HomeAssistant gismo) to automatically make use of free or very low cost tariffs when outside of the nominal 23:30-05:30 Octopus Intelligent Go tariff cheap rate period. I also need some extra connectivity to work the Modbus provided for remote monitoring.
Optimum Electrics, from Peterborough, were chosen as they could also do all the roofing work (new cedar shingles) and at ~£12,000 for the in-roof solar & storage system, they were competitively priced. They were very professional throughout and a pleasure to do business with. Apart from the two minor issues mentioned above, their service before, during and after installation has been excellent.
We already had a fair few rainwater butts, mainly old whisky barrels, the largest with ~500 litre capacity. But when they dry out, they leak a lot. So, this year, we installed a whopping 825 litre pillar rainwater tank in the corner – it’s not so pretty, but we’ll hide it with planting. It is yet to fill up!
Gas consumption is down ~20% and the electricity purchased is down by ~60% resulting in a significant cut in carbon emissions. Our house now has an EPC A rating. Bills are also down, especially electricity, which has decreased by 80%.
The solutions needed for our home are quite specific to our house: we needed to analyse the issues, educate ourselves and find the right installers. It took several years and we are not done yet – it’s a journey.
Our tips:
| Energy Consumption | Electricity (kWh) | Gas (kWh) | Wood (kWh) | Total (kWh) |
|---|---|---|---|---|
| Before | 4780 | 26453 | 3 | 0 |
| After | 2737 | 20599 | 3 | 0 |
| Carbon Footprint | kgCO₂e/m² | kgCO₂e/person |
|---|---|---|
| Before | — | — |
| After | — | — |
* Wood logs estimated at 2,000 kWh/m³. Carbon factors are applied according to the project year. Where a project start or end date is not provided, 2026 is assumed.
