Effective heating is essential for stable environmental conditions, but the wrong sort of heating can have damaging effects on the fabric of your building.
If you are considering a new heating system, you will need to find out whether you need permission to alter the interior of a listed place of worship.
Historic fabric benefits from a stable environment. You can help by providing a low, constant temperature which will help to get rid of damp and reduce condensation. The best temperature for the fabric is likely to be 8-10ºC (46-50ºF). You would need to boost this in advance of services or events to be more comfortable.
We do not recommend heating an historic place of worship to typical home or office temperatures because of the strain this puts on historic fabric.
Heating your building only in occasional short bursts is not advisable. This will cause temperature fluctuations, which will not control damp, might exacerbate condensation and might subject the fabric - especially roof timbers - to stress resulting from movement. We recognise, however, that some places of worship are in only occasional use and the heating regime will need to reflect this.
When planning a new heating system we advise you to first understand the effect this will have on your building. Creating statements of significance and need will help you consider the impact on the building's significance.
Alterations may range from excavation or cutting into walling to fit pipes, moving pews to make space for radiators. When planning changes, it is important to consider the ventilation of the building so that the new heating system will not create condensation problems.
You may also wish to consider the cost of any alterations when you are looking at options for new heating.
Types of heating
There are many types of heating systems and we describe the most common below, starting with the ones we are most likely to recommend.
Hot water systems
Hot water systems are generally the best way to heat a place of worship. They are the most suited to maintaining a constant temperature in your building and you can adjust them as necessary. Many places of worship have 19th or early 20th century under-floor ducts or radiators and we advise that you re-use these whenever possible.
If your place of worship has never had a hot water system, there may be difficulties when installing one due to the impact on the historic fabric. We would still recommend that you consider this sort of heating before other systems.
Electric storage heaters
Electric storage heaters provide background heat which you can raise when your building is in use.
Modern storage heaters are fairly small and slim and you can often locate them quite unobtrusively around the perimeter walls. Provided their installation does not require the removal of, or detract from the setting of, significant furnishings and monuments, Historic England recommends this form of heating.
Underfloor heating systems
Underfloor systems can provide a background level of heating which is beneficial for the conservation of historic fabric. They also lend themselves to working with ground and air source heat pumps.
Underfloor heating systems may indirectly cause damp problems, through the introduction of damp-proof membranes which, if incorrectly specified, can draw moisture into walls. When planning, consider leaving a sacrificial gap around the perimeter or using a breathable substrate to allow moisture to evaporate.
When considering underfloor heating, you will need to think about the challenges presented by accessing the heating if it needs repairing after installation.
Installing underfloor heating requires major alteration of the floor, either by taking up existing flooring or creating a new floor above it. Taking up the floor can have a significant impact on architectural character and archaeological remains, including of earlier levels, vaults and previous phases of building. See our page on Flooring for more details.
Creating a new floor level may be less physically damaging but will still have a major impact on the appearance of the interior. It will hide historic floors, and the level change will truncate columns and change the proportions of arched openings. Assessing the importance of existing floor finishes and levels will help you understand the impact of proposals.
Electric pew heaters
If you are only using a small area of a building at a time, these heaters can economically supplement background heat. You can also use them independently to provide short bursts of heat.
They are fairly unobtrusive and pew platforms can often conceal their wiring. We would not encourage you to affix them to seating of historic or aesthetic interest however, due to the damage that their attachment involves. They may also dry out the wood of the seating where they are attached.
Radiant (quartz ray) heaters
These heaters will generally not provide an acceptable means of heating your place of worship. Rather than heating the building to a steady temperature they provide short bursts of heat and will almost always be highly visible and unsightly.
Their radiation can damage nearby objects. As the radiation heats the object it strikes, they do not create a general feeling of warmth.
We generally discourage the use of these heaters. We recognise however that they may sometimes be justifiable in discreet locations or, exceptionally, in places of worship only used occasionally where there is no economic alternative.
These are gas-fired convector heaters each with their own boiler and flue. This means that installing them requires the creation of a number of openings in the wall, causing loss of historic fabric. The flues and their protective cowls are likely to negatively impact the external appearance of the building.
Historic England does not encourage use of this system.
Hot air systems
Hot air systems can be noisy and crude in appearance. They are not usually a good means of heating a place of worship.
Installing them may require the creation of a substantial opening within the external walls of the building to accommodate the air intake. Direct-fired air heaters also pump water vapour into the building, increasing the danger of condensation and producing deposits on the fabric.
Indirect-fired heaters are less harmful. Although they can be used to maintain a steady low temperature in the building, in practice such systems are generally used to heat the building rapidly for short periods, creating the problems discussed above.
Portable heaters, whether gas or electric, produce instantaneous, localised heating.
We discourage them as a lasting solution as they carry increased fire risk. Portable gas heaters also discharge water vapour into your place of worship, thereby increasing the risk of condensation problems in the building.