Jenny Love, currently completing a PhD at UCL Energy Institute, discusses her research on domestic energy efficiency
1. Please summarise your research project
I am investigating an effect called ‘comfort-taking’, which is about what happens when homes are retrofitted i.e. made more energy efficient with insulation. Comfort-taking occurs when occupants maintain a higher temperature in their house post-retrofit, along with or in some cases instead of saving energy.
‘Comfort-taking’ sounds like a deliberate choice but this is probably not the case. I want to know how and why occupants react as they do, to what extent their behaviour is deliberate and to what extent their behaviour is unchanged from before the retrofit.
My approach is to measure internal temperature and humidity in every room, the usage of each radiator, and to monitor which rooms occupants use. I am also gathering qualitative interview data from the occupants, both before and after the energy efficiency works.
2. Why have you taken this approach as opposed to measuring a household’s energy consumption over a given period?
Various studies have attempted this approach and postulated that observed changes in energy use are not as large as they might have been had the occupants not increased the temperature. But this requires modelling to make the jump from fuel bill data and observed temperature to actual behaviour.
I am avoiding this by observing behaviour directly. I will be able to tell if people increase or decrease their daily heating hours, start using and heating more rooms in their house, or if their home’s temperature increases. From my interviews I will be able to tell the extent to which any changes are deliberate and the effect of homes becoming more energy efficient.
3. What are your findings so far?
One possible behaviour change post-retrofit – that of deliberately increasing the thermostat or hours of heating since comfort is effectively cheaper – has not been observed in my dataset at all.
So far I am finding that occupants who understand heating controls are saving energy, whereas those who do not understand them maintain an increased temperature in their house and so do not necessarily save energy.
An example of this is when the thermostat is set so high that the house will never reach that temperature. Thus their boiler works flat-out, even after the home has been retrofitted, so no energy is saved and a higher temperature is recorded.
This finding is actually similar to an Open University study on heat pumps which showed that it was occupant understanding which led to lower energy use. My study is a bit different in design but is heading for a similar result in this regard.
4. What has surprised you during your research?
As part of my room occupancy monitoring to see if people change their use of space post-retrofit, I was surprised to see how often people move from one room to another. This has implications for zoned heating strategies which may be inappropriate if people are changing rooms as frequently as my data seems to suggest.
5. How do you feel the UK can best upgrade its housing stock?
I am an advocate of deep retrofit combined with proper occupant engagement. This is because in theory if a building has very low heat loss, it does not matter how the occupants behave – their heating demand cannot be very high. In practice, however, this statement is not always correct since buildings are sometimes not used as designed.
Therefore I think we have to treat the building fabric and the occupants with equal seriousness!