Heating and energy use
Heating the buildings is one of the main users of energy by a church, contributing most of that church’s carbon emissions which contribute to global warming and climate change.
Therefore your church’s heating system needs to be designed and run as efficiently as possible. This is part of our duty to care for God’s Creation.
The Church of England and Diocese or London have set a target of becoming net zero carbon by 2030.
Energy use from buildings is one of the main ways we generate carbon emissions which contribute to the causes of climate change. Carbon emissions are measured in carbon dioxide equivalent (CO2e). We usually say CO2 for short.
Altogether about 80% of the CO2 from church buildings comes from heating systems. Therefore we need to reduce emissions from heating drastically, even cutting to zero as soon as possible.
The cost of energy is understandably uppermost in most people’s minds. This is made much more acute by the crisis in gas supplies and costs which began in late 2021, made much worse by the war in Ukraine.
Energy and carbon due to heating
The energy we use in buildings includes electricity and gas and in some cases oil. Almost all gas and oil are used for heat. Roughly one fifth of electricity is also used for heat.
The amount of CO2 generated per kilowatt hour of electricity is less than for oil, and more than for gas. The CO2 efficiency of grid electricity has been improving fast, due to increased electricity generation from renewables. Therefore it is expected that CO2 per unit of electricity will soon fall below that for gas, and continue to fall after that. At the same time, CO2 emissions from each unit of gas remain much the same.
Therefore when we need to replace our heating, we need to think about switching from gas to electricity, and phasing out oil altogether.
If a heating system is in need of wholesale replacement, this may offer a golden opportunity for radical improvement, if possible moving to net zero carbon in a single jump, by switching to an all electric system, and purchasing on a renewable tariff. The Church of England publishes a list of the most ‘genuine’ renewable tariffs – see Switching to green energy.
Unfortunately, electricity costs about 3x the price of gas. How to mitigate the cost of electricity is discussed below.
Reviewing your heating system
One of the first steps for churches and people to save energy, carbon emissions and costs is to review our church’s heating system and its settings. It is important not to waste heat, and to run it at the lowest temperature consistent with comfort and health.
We should not wait until the system fails before optimising its current use and planning for when it will in the future need to be replaced.
Thermostats and settings
Comfort expectations have risen hugely. Heating should meet but not exceed minimum comfort standards – members of the congregation should not expect to be wearing shorts and T-shirts in church in February!
Ordinarily, anything in the range 16-19 deg C may be appropriate in different church buildings, with an average somewhere in the middle of that range. From 2022 there is a very good case for keeping settings even lower, say 15 deg C. This would mean we need to wrap up warmer in winter.
Just a one degree reduction may be expected to save approximately 8-10% of heat energy.
However, the wellbeing of the elderly and infirm and young children, and people who may have been brought up in a hotter climate that the UK, should of course be taken into consideration. As well as the church’s spending on energy. Tragically, some members of any congregation may be suffering fuel poverty. The church may become a refuge for people who have nowhere else to keep warm.
Boiler-driven systems will have a thermostat on the boiler itself, and another wall-mounted at some central point.
The wall/room thermostat controls the temperature in the space – the boiler power and thermostat control how quickly and efficiently it reaches it. An optimal location for the room thermostat is critical to efficient energy management.
Individual heaters or radiators may also have thermostats – if not, it is well worth installing thermostatic radiator valves (TRVs), and making good use of them, at least where a space is partitioned into smaller rooms.
Programmable TRVs are now available – you don’t have to keep fiddling with them!
The exact amount to lower the temperature depends on the current setting; whereas the optimum setting depends on the efficiency of the heating system, and the thermal characteristics of a building.
It is very energy and cost effective to install the latest intelligent time and temperature controllers to hot water boilers, immersion heaters and any circulating pumps – so that they are set to provide heated water only when needed.
Typically, programmable controls will now use internal and external temperature sensors, selecting optimum settings in relation to both.
In exceptionally cold weather, it may be justifiable to turn up the heating temperature, especially if the heating is zoned, enabling concentration of heat where it’s most needed.
A higher setting may be needed to achieve minimum comfort, due to temperature drops towards cold spots.
Alternatively, meetings can be moved from the main church space to smaller rooms. These may heated independently often with electrical heaters. This avoids wasting heat by sending it round the whole circuit for the sake of one smaller space.
However, electric portable heaters should be avoided if possible. Gas portable heaters are dangerous, and a ‘no no’! Any portable heaters are a potential hazard and may compromise your church’s insurance cover (ask your insurer). (The same may also apply to free-standing lights or fans.)
Turning down the knob applies to heating, but not in the same way to hot water.
A minimum of 60 deg C is usually the right temperature for stored hot water – for at least one hour per day – too hot for legionella (any higher temperature increases the risk of scalding).
For vessels with a programmable thermostat, it is advisable to programme the maximum temperature to end just before any time when showers are taken – to stop harmful bacteria getting onto shower heads – and immediately after the end of any period of shut-down. A lower temperature, say 40 deg C, can be programmed at other times.
Hot water storage is not likely to be needed in a church. An instantaneous electric heater may be sufficient to supply the taps.
- Ensure heating the heating season is programmed appropriately, but be prepared to override it depending on the weather;
- Make sure there are no unnecessary obstructions in front of radiators, heaters and air ducts;
- Bleed your radiators and have them cleaned on a regular basis, to ensure water circulates properly. Clean off the fluff and dust from the grill and filters of convector radiators and heaters;
- Check for draughts and damage to windows, window frames and doors. Repair any damage and install or maintain draught seals where there are air gaps. Contact the Parish Property Support Team which runs the Diocesan Advisory Committee (DAC) regarding any repairs to window glazing;
- Avoid opening windows directly above a radiator, or turn the radiator right down below any open window;
- Make sure that your heaters and boilers are serviced regularly, at least once a year, and ask for a report on combustion efficiency;
- Insulate hot water tanks and piping. You do not want expensive heat leaking out.
Churches tend to be stereotyped as ‘cold and draughty’. Of course, some are that. It is not usually because they are unheated, but rather because so much heat needs to be emitted in order to warm up the interiors of what are generally large buildings.
In addition to considering temperature settings, it is important to improve insulation where feasible.
Church roofs are often cavernous spaces, through which up to a third of the building’s heat can be lost. If your church has an empty loft space, filling it with insulation could prevent the lion’s share of this heat escaping.
If there is no roof void, insulation may sometimes be incorporated in the roof structure, though this may need to wait until the roof is due for replacement. Whether insulation is feasible may depend on the type of roof and the detailed design at its edge, depending on whether there is an eaves or a parapet.
Historic buildings require natural ventilation. Care must be taken when considering any insulation in churches to ensure that no harm is done to the building fabric.
It may also help to prevent heat loss if there is a possibility of cavity wall insulation, where there is a gap between your inner and outer walls. This may sometimes be feasible for a newer church hall, for example.
However this is rarely possible in pre-1914 church buildings as these are generally of solid construction and do not have cavity walls.
You should consult your Quinquennial Inspector (QI) about any proposal for insulation. You are also likely to need a faculty, for which the Diocesan Advisory Committee (DAC) will need to be consulted – contact the Parish Property Support team.
Replacement heating systems
If your boiler or heating system has failed or broken down, or is requiring frequent repairs, or in some cases just if it has suffered a drop in efficiency, then you should upgrade to a new system. This will need to be much more fuel efficient.
Getting permission for a new heating system
Most projects for church heating will require a faculty, or permission from the Archdeacon. The Diocesan Advisory Committee (DAC) needs to be consulted, at which point the implications for energy and carbon will be taken into consideration.
Every case still needs to be considered on its merits.
Options for your heating system
Options need first to be explored with the Head of Environment & Sustainability, and Parish Property Support who run the DAC.
Methods of heating churches vary, from traditional ‘wet’ radiator and pipework systems, usually driven by one or more gas boilers, through fan convectors (gas and/or electric) to electrical heat systems including radiant panels and heat pumps. Some churches will have a combination of different types of heating in different parts of the building.
All electric heating
Electricity has hitherto been disfavoured as a principal heating method – it can be very wasteful and expensive. However as explained above, we are going to need to switch to electricity, as it becomes increasingly low carbon.
An efficient heating system also needs to save on costs. We want to switch to electricity, but as mentioned, electricity is about 3x the cost of gas. Therefore an electrical system needs to be much more efficient in keeping the building off the chill, while providing heat to the congregation.
Electricity can be deployed more efficiently by using it to power a heat pump, which may deliver 3-4 x the energy in the form of heat as the kWh of electricity consumed; and what electricity is still required to be drawn from the grid may be supplied on a renewable tariff.
Unfortunately a heat pump is often the least viable option for a church, as the heat delivered is at relatively low temperature, requiring a high level of insulation to avoid it being dissipated. A heat pump may be more viable in conjunction with underfloor heating.
High temperature heat pumps are starting to come onto the market, but they are less efficient in terms of heat output compared to electrical energy input.
Every church needing to renew its heating all or in part (including the boiler alone) is strongly encouraged to look at these and other electrically powered options, such as electrically powered fan convectors, far infrared panels, or pew heaters.
Far infrared panels differ from more old fashioned radiant panels, which glow red and can be uncomfortable. By contrast, far infrared is colourless, does not glow and can provide a more gentle warmth.
Electricity may be generated on site by a church’s own photovoltaic (PV) solar panels. In the long run, this should help reduce running costs.
Low and zero carbon heating options
As mentioned, a heat pump system is one low energy low carbon option, though not zero carbon.
One near zero option is a biomass heating system. This has become controversial due to the large scale import of biomass from clear-cutting of forests, to be used in electricity generation. However these considerations should not apply to small scale on-site biomass heating. Nevertheless there are a range of other factors needing to be thoroughly considered.
Low carbon fuels
It is possible that in the medium to long term, biogas (so called ‘green gas’) may become more available and viable through the gas grid. At the moment this is not price competitive.
We are only aware of two tariffs which are genuinely net zero for biogas (biomethane), injected into the gas grid. Considerable caution is needed before adopting such a tariff, eg where does the gas come from? Is it from factory farming or abattoirs? Options are needed that are both ethical and price competitive; and also available at scale.
There is also the longer-term prospect of hydrogen being introduced into the grid. This is likely to be 20% of the supply to begin with, the rest being methane. The proportion may increase in steps – National Gas (formerly National Grid Gas) aims to deliver 100% hydrogen by 2050.
Most or all gas boilers are already 20% hydrogen ready – however if replacing your boiler you should check.
Hydrogen is classified as ‘Grey’, ‘Brown’, ‘Blue’ or ‘Green’, depending on how it is generated. At present, only ‘Green’ hydrogen, generated by electrolysis using renewable electricity, is 100% renewable. Once the electricity grid is decarbonised (which the UK Government aims to achieve by 2035), any hydrogen produced by electrolysis will be Green. However, Green hydrogen is not currently economically viable.
The benefits of using hydrogen to heat buildings are currently doubtful. It can be more efficient to use use hydrogen in mobile situations, eg to run a bus.
Replacing a gas boiler
A new gas boiler is very much the last resort. There are occasions where only the boiler needs to be replaced. Even then more radical alternatives need to be considered, which take account of the need to move to net zero status by 2030.
It might be easier if there were suitable electric boilers to serve traditional hot water radiator circuits. These exist at domestic scale; but aren’t yet quite viable at a larger scale. This is partly because they require a 3 phase power supply.
Of course, when an older boiler is replaced by a new gas condensing boiler, this may offer considerable efficiency savings. But those savings are maximised only if the boiler does actually condense. This means being programmed to run at a low temperature, which heating engineers often find unfeasible. It is easier if the heat is not needed to provide hot water – which must be heated to minimum 60 degrees to prevent Legionella.
There may be a case to adopt a hybrid system. employing a gas boiler for low temperature background heat, together with another source to heat the space rapidly before services or events. More on this in the next section.
Where it is unavoidable to install a replacement gas boiler, it may have to be retired early, even within the 2020s. That may enable a parish to avoid even greater expenditure now, while keeping the heating running for the next winter, and being afforded a breathing space to plan how to grasp that nettle in a few years’ time. But it’s better if a parish can avoid the crisis of a failed boiler by planning ahead.
It may not be possible to get rid of traditional gas completely by 2030, maybe not even by the UK’s 2050 deadline. That means offsetting will be need to meet net zero targets sooner. Until we can access biomethane from an acceptable source, we may have recourse to suppliers of North Sea gas who include offsetting as part of their gas tariff. Some such supplier also offer renewable electricity. This ought to be considered as a minimum, as soon as any current contract comes up for renewal.
In some cases there may be acceptable hybrid options, where part of the heating load is taken by new electrical heaters eg pew heaters or far infrared heating panels.
This may leave only a residual need for week round frost protection in cold winter weather.
Paradoxically that may enable a new or existing boiler to last much longer, but if new it may be a smaller boiler, set to a lower temperature, and the gas consumption may be easier to offset.
Heating your Church (Church of England advice/guidance)
Church Heating (DAC advice)
Lighting and energy use
Climate Action Projects
Climate Action Finance.
Gas and Energy Supply and Prices Crisis
Switching to green energy.
Head of Environment and Sustainability
Parish Property Support Team
Getting your faculty.
Environment and Sustainability, front page.