What is a church?
Most Danish church buildings are from the Middle Ages, which is significant when making changes to the church.
For churches less than 100 years old, changes can be made to the church without having to apply for a permit. Churches older than 100 years, however, must apply for a permit from the diocese. This also applies when making modifications to the heating system.
Permanent and periodically heated churches
When dimensioning the heating system of a church, it is significant whether the church is heated on a permanent basis, i.e. the church is in use more or less every day of the week. Or whether it is a periodically heated church, i.e. only in use 1-3 times per week.
Furthermore, it is of interest whether the church has uninsulated vaults or is insulated using flat wooden ceilings.
The heating system must be bigger in periodically heated churches with uninsulated vaults, than in a church of the same size which is permanently heated and where there are flat insulated wooden ceilings.
Other similar buildings
The information regarding heating in churches, both medieval and more modern, is relevant to other large buildings with meeting halls and office facilities that gather many people on a regular basis.
Energy savings in church buildings
Energy savings can be achieved in various ways: optimizing the building, its heating systems and other technical installations, and through changed behavior and everyday operation.
Reviews of almost 700 churches in Denmark* show that average energy cost savings of approximately 40% can be achieved. Replacing heating systems contribute to about a third of these savings. Examining other technical installations (primarily lighting) and particularly behavioral change and daily operations (heating control) thus hold great potential for savings.
Many churches are outdoor illuminated during the month of December. Some are illuminated several months in winter. Replacing outdated halogen or high pressure sodium bulbs with LED spotlights along with using timers and twilight relays, can give reasonable savings.
Inside churches, the predominant light source is "church candle bulbs" (kirkekerter). They are less energy efficient than incandescent bulbs, but until recently it has been difficult to find LED bulbs, that could provide the same aesthetic expression and light quality with the characteristic ‘warm’ light. But such candles are on the market now. Whether replacing the bulbs is profitable depends on how many hours the lights are on annually.
Churches are normally much less in use than houses, offices, etc. Many churches, especially village churches, are in use only once or twice a week. At the same time, church buildings are often poorly insulated. The temperature of the church when it is not in use, is therefore crucial with regards to energy consumption.
The Ministry of Ecclesiastical Affairs’ Heat Circular prescribes a temperature of max. 8° C for time periods between services. This is recommended primarily from a conservation perspective, but it is also an important energy cost-cutting proposal.
In addition to the choice of base temperature in the church, it is important - with regards to energy consumption - when the heat is turned on. Many heating systems are capable of raising the temperature in a short span of time - if they are properly dimensioned. It will often be appropriate to turn on the heat during the night before a worship service. A good and user-friendly timer system is therefore important, so that the heat can turn on automatically at the appropriate time. If the heating system only can be switched on manually, the heating time will often be 4-6 times longer than necessary, resulting in a large waste of energy.
Optimal heat management depends a great deal on each individual church, moisture conditions and how the church is used. It may therefore be necessary to review and possibly map the indoor climate of the church using a data logger.
*Conducted by Energitjenesten (Energy Services)