Suggestions About Air Conditioning Worship Spaces

From the Interfaith Coalition on Energy. May, 2000
It’s Cooling Time, Just Like it was Last Summer…

We don’t want you to install air conditioning because we are in business to help you lower your energy use, not increase it. 
Anyhow, here are some guidelines we send to congregations who are considering air conditioning:

  • Air conditioning is expensive to install and can be unsightly.  A central air conditioning system may require that you install a larger electric service to the building, so include those costs with the installation costs.
  • The older the building, the more likely you will have to upgrade the service.  Worship spaces registered as historic sites should be very sensitive to outside air grilles and the placement of condensing units.


  • Air conditioning can be expensive to operate. Don’t forget to include the annual maintenance costs in predicting the operating expense. Once it is installed, members of the congregations may want to run it during all funerals and weddings.  Not to do so, unfortunately, may be considered dishonorable.


  • Not all members of congregations appreciate air conditioning, particularly if the air flow dumps excess chilled air on the pew they have occupied for generations.  Other members of the congregation may resist air conditioning because of environmental reasons because air conditioning is on-peak both seasonally and daily, forcing utilities to add generation capacity more than any other type of load.
  • Older worship spaces usually have natural ventilation systems.  Often, these have been closed off to save heating energy.  If the ventilation is used during the summer only, it can be very effective.  Examples of such systems include vents or doors into the base of tall steeples, large grilles in ceilings, which open into ventilated attics, and airshafts in walls and partitions.  Appropriate use of natural ventilation may eliminate the need for air conditioning.
  • If natural ventilation systems are not adequate, ceiling fans may offer comfort.  Ceiling fans should be used only in the cooling season; they have no benefit or negative benefit during the heating season.  Ceiling fans have to be installed above the lights to prevent flickering.  Fans should be high quality, industrial-grade, three-bladed fans, each on a separate variable speed switch.  They should blow down only, not up.


  • If you install air conditioning, you may not need a very large system.  Before sizing it, we strongly recommend that you lower your cooling load by installing lighting that uses less wattage.  Air conditioning equipment will probably be oversized if you size it according to the warmest and most humid conditions.  Instead, size it to allow for pre-cooling before and in between services.  Toward the end of the service, the space may become warmer but still tolerable on the hottest and most humid days.  Sometimes, all that is required is a very small, ductless split system for the choir loft.  Smaller systems require single-phase electricity because they are designed for the residential market.  Above five tons, systems often require three-phase power, which necessitates a new electrical service to the building.
  • Some codes require outside air at 15 cubic feet per minute per occupant.  Since worship spaces are large and leaky, such outside air requirements may not be necessary.  If a system is sized for outside air for hottest, most humid day with filled pews, the air conditioning system may be way oversized.
  • Avoid cutting edge technology.  Choose middle-high-efficiency, commonly available equipment because the cost of installing fancy technology is higher, the availability of parts is lower, and the chance is greater that its manufacturer will orphan the new technology.  Pick equipment so that when you have an emergency, the repair person is more likely to have replacement parts already on his truck.  This means avoiding thermal storage, gas-fired heat pumps and ground source heat pumps for the time being.  For your home, you would be better off choosing equipment that is very efficient, but the relatively few hours use of a worship space are so few that high efficiency equipment does not have as great an impact on electric costs.
  • Avoid complicated system controls.  Unless you are sure you are going to have computer-literate, well-paid facility maintenance personnel from now on, don’t install computerized control systems.  You can control energy use with digital clock thermostats.  With anything more complicated than that, the instruction manuals will get lost, people will try to bypass the controls and you will become very frustrated.  Since weddings, funerals and special events change your operating schedule, make sure the controls are flexible and easy to program.  Remember, setting a lower temperature will not make the system work harder… it will just make the room colder.
  • Make sure you can easily access the equipment to change filters.
  • If you add air conditioning, you should find out what your rate options are from your electric utility.  Often, shifting to an off-peak rate will lower cooling costs.  PECO Energy offers the Night Service Rider.  PECO’s off-peak times are 8pm to 8am weekdays, from 4pm Friday until 8am Monday, and also includes major holidays.  If you are paying for demand (kilowatts) as well as usage (kilowatthours), and you don’t qualify for an off-peak rate, you may want to consider interlocking the compressors so they don’t all operate at the same time.
  • Once you install air conditioning, keep it off whenever possible.  It may take as short as a half hour to pre-cool with air conditioning, and a bit longer if it is very hot and humid.


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