In some areas of the country, water heaters, both gas and electric, are installed in attic spaces. As with all gas water heater installations, it is very important to have sufficient combustion and dilution air to insure proper drafting of the exhaust products and safe water heater operation.
As outside temperatures increase, the need for proper combustion air and attic ventilation becomes even more critical. For reference, if not ventilated adequately, attic space temperatures can go as high as 160 degrees Fahrenheit. This can occur when outside air temperatures are only in the 90’s; even when the sky is cloudy.
As the pilot flame burns, it requires oxygen from the air. The exhaust products from the pilot flame are then designed to rise through the combustion chamber and water heater flue, exiting the roof through the chimney system. This "draft", while removing exhaust products, also brings in "fresh" air to the combustion chamber.
For the exhaust gases to rise through the water heater and chimney system, they must have a temperature much greater than their surroundings. Elevated attic temperatures make it extremely difficult, or impossible, for the water heater combustion system to properly "breath". Without the ability to sustain the main burner and pilot flame with fresh air, the pilot flame will become unstable, and may eventually go out. When this occurs, the water heater will not function.
To avoid these water heater outages, proper attic ventilation must be present. Examples of common practices to insure sufficient attic ventilation include soffit vents used in combination with ridge vents and/or mechanical attic exhaust fans which are turned on and off via temperature controls.
Soffit and ridge vents allow for natural convection of the hot attic air to be removed form the attic, and fresh air to enter at or near the floor level of the attic. Mechanical attic exhaust fan systems power the air flow and may cycle on and off as the temperature rises and falls. Both are acceptable and common methods used. However, undersized, blocked or improperly located attic ventilation components result in elevated attic temperatures and possible water heater outages. Consult your local construction and roofing experts for further information about proper attic ventilation.