Challenging assumptions about how people in Ireland heat their homes
Heating is the single most energy intensive activity that takes place in Irish homes, but we haven’t had a good picture of how people actually heat their homes – until now.
Why is measuring heating behaviour important?
Assumptions about heating behaviour are central to energy performance models, such as the Dwelling Energy Assessment Procedure (DEAP) that underpins the calculation of a dwelling’s Building Energy Rating (BER). The DEAP assumes that a typical household heats their home for 8 hours a day – from 7 am to 9 am and from 5 pm to 11 pm – during the October to May “heating season”.
However, these assumptions are not based on evidence about real human behaviour, and several international studies measuring heating schedules have found that models like the DEAP are overestimating how much people heat their homes. There are very little data specifically from Ireland. One small study of 67 homes, run from 2011-2013, found that the heating was used for about 5 hours a day, but these were primarily retrofitted detached houses within a small geographical area in Tipperary, and are unlikely to be representative of the wider population.
Ireland's Behavioural Energy and Travel Tracker
The Behavioural Energy and Travel Tracker (BETT) is a nationally representative online survey designed by SEAI's Behavioural Economics Unit. The trackers uses a behavioural science technique known as the 'Day Reconstruction Method' to gather accurate and granular data about travel and home energy behaviours in Ireland. It also collects data on factors that may be related to energy behaviours such as psychological factors, energy poverty, dwelling and sociodemographic characteristics. BETT ran monthly from December 2022 to December 2023 and continues to run on a quarterly basis.
New evidence from the Behavioural Energy & Travel Tracker (BETT)
Since 2022, my team has been gathering detailed information about the everyday energy behaviours of people in Ireland through the Behavioural Energy & Travel Tracker survey (BETT). We recently released a report based on monthly BETT data from 2023 that takes a closer look at heating behaviour.
In the report, we find that during the heating season of October to May, people heat their homes for an average of just under 4 hours a day, about half the duration assumed in DEAP. Just 15% heated their homes for 8 hours or more. Interestingly, when we look specifically at detached homes, we get a very similar estimate of heating duration as the previous Irish study mentioned above. Although our estimate is based on self-reported data, it has the distinct advantage of coming from a very large (1,000 participants for each of the 12 waves) nationally representative sample.
The report also includes findings on how a variety of factors affect heating behaviour. For example, we find that households with oil boilers are much more reliant on secondary heating (e.g. open fires and stoves) than those with gas boilers. Psychological factors – including worry about cost of living and climate change – also matter, albeit in different ways. Those worried about the cost of living were less likely to use heating in the first place, but those worried about climate change tended to turn the heating on for less time and use lower thermostat settings.
What does this mean for energy performance models?
Of course, heating behaviour will vary a lot from household to household, and simplified models like the DEAP are not meant to accurately predict how much energy a given dwelling will use – the BER is an asset rating rather than an operational rating. However, if models are systematically overestimating the average heat demand of a home, this will have an impact on comparisons between dwellings and may partially account for the smaller-than-expected difference seen in real energy consumption between dwellings with different BERs. Basing assumptions of behaviour on normative views of what a “typical” Irish household should look like, such as the nuclear family, also runs the risk of disadvantaging households that do not fit this mould.
With changes coming to the BER scale in the next couple of years through the EU’s Energy Performance of Buildings Directive, now is a good time to revisit the assumptions about human behaviour being made in these models to make energy performance ratings as informative as possible for citizens.
