By Nicola Terry
Moving to zero carbon heating in homes is going to be a significant change to our heating patterns. Many of us have central heating with a gas or oil boiler. There is talk of gas boilers being converted to hydrogen – but this will take many years even if it happens. The majority of homes how have central heating and for these the obvious switch will be to a heat pump because that is by far the most efficient way to heat with electricity. However, heat pumps are best used to provide gentle heat over long periods whereas we are used to heating for short periods on demand.
In this post we take a look at our current heating habits, as determined by the Energy Follow Up Survey , part of the English Housing Survey. You could be forgiven for missing the fanfare (there wasn’t one), but EFUS is one of the most significant releases of information about current heating practices in UK homes, only published once a decade. EFUS is a complicated survey of several thousand households, comprising questionnaires and, in some cases, temperature logging over several weeks in winter and summer. The original surveys were done in 2017, but temperature logging continued into 2019 and the latest reports have only recently been published.
What timer controls do we use?
The diagram below shows the heating types and typical central heating timer controls. It shows that a fifth of households are used to turning their heating on and off manually.
Existing electric heating systems will not need to change in order to be low carbon (savings will accrue because of continued decarbonisation of the grid). These systems are usually installed in smaller homes and flats, and even though a heat pump could be more efficient there may not be room. ‘Other’ heating means solid fuel, gas fire or communal heating. This might well need to change.
For central heating with a heat pump, the standard recommendation is to heat all the time. This allows you to use a lower radiator temperature and get more efficiency from your heat pump. If you prefer not to do this, you should not ramp the temperature up quickly. For example, you might allow the temperature to drop 2°C overnight and then turn it up in two stages in the morning, with an hour for each stage. Homes that are well insulated will not cool down much anyway, and heating for longer will not add much to bills. However, for inefficient homes, heating all day can add 20% or more to the bill.
What do our heating patterns look like?
For homes with central heating, the most common heating pattern is twice a day heating, but it is very variable. On weekdays, the following are typical:
- No regular pattern (28%) – heating typically 5-10 hours on a week day
- Regularly twice a day (58%) – total 7 hours’ heating
- Regularly three times a day (19%) – 7.5 hours’ heating
- Regularly once a day (23%) – 14.5 hours’ heating
At weekends households heat for a little longer, and a few more households heat once a day (27%).
Tenants in social housing (registered social landlord or council housing) have slightly shorter hours of heating – about one hour less – and households with pensioners tend to heat a little longer, but just an extra hour.
What temperature controls do we have and how do we use them?
Most homes with central heating have a main thermostat and TRVs. However, 11% have TRVs with no thermostat and 10% have thermostats but no TRVs. In homes with TRVs they can be used to turn the heating off in rooms that are rarely used. Over a third of households do this.
Good heat pump engineers advise us to keep all the TRVs open. This is for several reasons. Firstly, when the home is warm and TRVs are mostly off, that means the volume of water circulating in the heating circuit is low and when the boiler/heat pump does come on it does not take long to come up to heat. This can cause it to switch on and off frequently (‘cycling’), which reduces efficiency. Cycling is bad for boilers as well as heat pumps but it is worse for heat pumps. Some controllers try to avoid cycling by having a minimum period ‘on’ and ‘off’. However, if the water volume in the circuit is very low this means heating the small volume to a higher temperature which, for the heat pump, reduces efficiency. You can get around this by having a buffer tank but that takes up space.
The second reason is that when you have different temperatures in different rooms heat leaks between them. This adds load to the radiators in the rooms that are supposed to be warm, which means that you may need a higher radiator temperature to supply the leaking heat. High radiator temperature means lower efficiency. Depending on your particular situation, the loss off efficiency can more than make up for the savings from keeping one room cool. You can reduce this heat leakage by having insulation in your internal walls, but this is rare. You would also need to keep doors closed of course.
What temperature do people set the thermostats to?
Some people like it warmer and others cooler. No doubt some would rather be warmer but are worried about bills. This chart from EFUS shows the typical thermostat settings in homes that use a main thermostat, based on a survey of just under a thousand homes. In most homes the range is about 15°C to 25°C, but half of homes are in the narrow range 19°C-21°C.
Reported thermostat settings for homes with central heating
The majority of householders (61%) generally leave the thermostat at one setting but the rest vary it according to how they feel or at different times of the day.
When it comes to heat pumps, if you like your home to be rooms very warm you may need a bigger heat pump and larger radiators. The main change you would need to make is not to turn the thermostat up more than about 1°C at a time. Otherwise, if your controller is intelligent It may increase the radiator temperature to try to respond quickly – and this will lose efficiency. Or you can tweak the flow temperature manually with the same effect. If your radiator temperature stays the same, the house will warm up rather slowly and you will just have to be patient.
Many homes with central heating also have a gas (34%) or an electric fire (33%) in at least one room and in 39% of homes these are regularly used in winter. Mostly this is the living room (81%) but sometimes a bedroom (7%) or a conservatory (4%). One hopes the central heating is not used for the conservatory as this can be a major heat loss.
People use these extra heaters for several reasons. The survey allowed respondents to tick more than one box here so the numbers add up to more than 100%:
- ‘To heat the room being used instead of the whole house’ (46%)
- ‘The main heating is not enough in this room’ (31%)
- ‘We like the look and feel of the extra heater’ (41%) – in this case it is usually a stove or an open fire.
With a heat pump, the same reasons could still apply. Even if you heat the whole house all the time, you could choose to heat it to a few degrees lower than comfortable and top this heat up in the room you are using with an electric heater. Or, if one room was very exposed and you did not want to turn up the radiator temperature just for that one room, you could use an electric heater to top up the heat in that room. However, in that case it is especially important that the extra heater is has its own thermostat as you don’t want to overheat that room.
Are we warm enough?
Most people feel a bit chilly sometimes in the winter. This is more of an issue in living rooms than bedrooms. For living rooms, a third are never cold but 12% are cold often. For bedrooms, half of households are never cold and only 9% often. There are real differences behind these feelings, as shown in the table. However, the differences are much less than the range of thermostat settings. Note the table shows average temperatures (including when heating is off), not just thermostat temperature.
|Mean temperature …
Homes with poor EPC ratings (F or G) were more likely to be uncomfortably cold. The poor rating can be due to a combination of inefficient fabric, or an inefficient heating system – typically room heaters rather than a central heating system. Either way, F and G homes were definitely cooler, averaging 17.2°C in the living room compared to A to C homes averaging 18.6°C. If this is due to fabric, then the temperature will drop quickly when heating is not on which brings down the average.
When more homes have heat pumps, homes that are currently cold are unlikely to improve, unless efficiency measures are installed. Draughts were most often blamed for cold in the living room (49%), which is encouraging as some draughts (such as draughty floor boards or windows) are fixable. However, EFUS did not indicate the location of the draughts. In bedrooms, lack of insulation was usually blamed and this may be more expensive.
More than a quarter (27%) of EFUS respondents report damp and/or mould patches in their homes. Condensation is the most common cause, which suggests problems with insulation. Homes are more likely to have moisture-related problems if they are:
- older, especially with solid walls – pre-1919 homes are the worst, with 39% having problems
- rented – the private rented sector is the worst, with problems in 41%, compared to 20% of owner-occupied homes, or
- low EPC rating – but even in the A-C ratings, 22% had damp and mould issues.
The Energy Follow Up Survey tells us how people heat their homes now. This shows that for those of us switching from central heating with a boiler to a heat pump, we will need to adapt our habits somewhat. Mainly this means heating for longer, or with a higher overnight temperature. Turning down the radiators in unused rooms may no longer be effective as an energy saving measure. However, we can still use supplementary heating more or less as before, as long as it is electric or burns biomass.
Homes that are cold now will benefit even more from extra insulation and draught proofing. It is sensible to do this before switching to a heat pump. What remains unknown for most homes is what specific action to take to improve insulation and tackle draughts – and this requires a detailed survey of each home.
 BEIS (September 2021) Energy Follow Up Survey (EFUS) 2017 reports. London: BEIS.