HVAC Considerations - How to Make Your Building More Comfortable During Very Hot Weather

By Robert C. Foreman, Architect, AIA, LEED AP

Recently a client called whose church building was completed several years ago. It was mid summer and temperatures were soaring to near 100 degrees. Their complaint was that their building just wasn’t comfortable during the morning services, but was usually ok by 6 p.m. when outside temperature was actually hotter. Upon investigation we learned that the sanctuary air conditioning was turned off most of the week and was being turned on at 7 a.m. Sunday morning. At 7 a.m. the interior temperature and humidity were very high from the system being shut down all week. At 8:30 the early service started and the sanctuary was partially filled with people. These people were bringing in more heat and humidity and loading the system before it had been running long enough to meet comfortable temperature and humidity levels. This kind of problem is very common with churches.

There are also added benefits in conditioning a space correctly. Excessive temperature and humidity variations have a bad effect on pianos, organs, and other furnishings. They can also cause building materials to crack or move, especially large spans of gypsum board.

Our Recommendations:

• Never shut a system "off". Heat and humidity are very hard on pianos, organs, pews and other furnishings. Use an "unoccupied" setting. Never let the temperature exceed 80 degrees Fahrenheit in Summer or fall below 60 degrees Fahrenheit in Winter.
• Using an "unoccupied" setting will reduce humidity build-up, avoid humidity damage to facilities and allow the space to reach comfort level sooner after being set to "occupied."
• We recommend setting timers to switch to occupied status at least twelve hours before planned use. This way the system can be removing excess humidity from the air and from the walls and furnishings, and reach comfort level before services start.
  
• Most systems are designed to only be able to cool to about 15 degrees below outside temperature for any extended period of time. Therefore, in very warm weather, above 90 degrees, it may be necessary to "pre-cool." Do this by setting thermostats 5 or 6 degrees lower than normal, well in advance of use. When people enter the space, they may feel chilly, but by the time the service is over the temperature may have already climbed above the comfort level, due to the number of people and the introduction of outside air as they enter. However, during most of the service, people will be comfortable.
  
• Always set fan settings to run continuously when system is in "occupied" status. We recommend this for year around use.
• Reduce the use of drama lights and dim platform lighting to reduce heat gain from lighting during the summer. Lights add heat to a space. Turn lights off until you need them.
• Keep outside doors closed. Ushers and greeters should help keep doors closed to limit the introduction of warm humid outside air.
• Reduce outside air intake settings on the HVAC system. The codes require public buildings to have a certain percentage of outside air intake. There are good reasons for this, but sometimes it makes sense to reduce these settings during extremes of temperature and humidity. This may require help from a qualified HVAC technician.
• Service your HVAC system on a regular basis. Change the filters on the recommended schedule. When was the last time the system was serviced? We recommend that you consider using a qualified HVAC servicing company under an annual service contract. You have too much invested in your heating and air conditioning system to neglect its maintenance and upkeep.
•  If all else fails, make August "casual Sunday month". Ban coats and ties and wear "summer" clothing.

If you follow the above advice, your people will feel more comfortable. It is possible that operating costs will be lower and that maintenance costs will be less in the long run.