New York Landmarks Conservency
Common Bond

On those scorching summer days when the perspiring faithful shift in their pews and determined clergy put mind over matter to resist wilting in their robes, how can relief for the body be found in the house of worship?

Installing a costly air conditioning system that brings in high electricity bills is not the only solution. Historic houses of worship were usually designed to allow hot air to escape through windows, events, and flues in clerestories, attics and towers, as pointed out in a recent newsletter article by Inspired Partnerships of Chicago ("Restoring Long Lost Ventilation," Amazing Grace, Summer 1995).

"The original designs would meet contemporary building codes for healthy natural ventilation," says mechanical engineer Ralph Mottola, P.E., of Mottola & Poet, New York, NY. "But in many religious properties, concerns about heat loss in cold weather, security, or misunderstanding of the system have led over the years to the closing off of many sources of ventilation."

For example, most protective glazing systems installed over stained glass windows prevent the original ventilating panels from being opened. A desire to restore operable windows could be one of many factors contributing to a decision to remove old secondary glazing. Restoring natural ventilation is a first step that is certainly economical and may provide sufficient comfort to ward off the expense of a mechanical cooling system. "Masonry buildings are particularly good at retaining cool nighttime temperatures through the morning," Mr. Mottola explained. "But by mid-afternoon, the indoor temperature will often approach or reach the outdoor temperature." Experiment with closing doors and lowering windows to reduce inflow of warm air, while keeping upper level ventilation open so hot air can escape.

If natural ventilation still leaves the interior uncomfortably warm during most hours of use, air conditioning may be an option. A mechanical engineer can perform a conditions survey of existing systems, look for hollow spaces above the sanctuary where ducts can be installed, and provide recommendations and a cost estimate for improving cooling. Avoiding damage to significant interior features and finishes and inconspicuous placement of exterior mechanical equipment are important concerns. A Building Committee, preservation consultant, or architect attuned to these issues should be involved. "Choose a simple, easy-to-maintain system," advocates Mr. Mottola. And if the congregation is considering using ceiling fans in the summer, the air movement may make people feel cooler, but the warm air of the sanctuary is being pushed down.

Using Natural Ventilation

Open basement windows (screens and iron security grilles are often required) to reduce condensation. Open windows in sanctuary to increase air circulation. Check condition of ventilating sash in stained or leaded glass windows. Creaky, corroded frames, and hardware should be repaired to avoid breaking glass. Investigate attic for ceiling vents and flues that may be blocked and can be restored to use. Where suitable, install dampers so they can be easily opened and closed. Check condition of attic exhaust fans, thermostats, and wiring. Investigate towers and steeples for vents and trap doors which can be left open to create updrafts. Use screening to keep out birds and animals.

Above, An Attic flue exhausts hot air from the sancuary through the roof. Above, a ventilating skylight in dome-shaped housing is effective at cooling attics.