AIR FLOW IN DUCTS

Air Flow in Ducts



Air Flow in Ducts

Air Flow in Ducts

Studies indicate that 10%-30% of the heated or cooled air is lost—along with the money spent to heat or cool that air—through leaky ducts. Properly sized, installed, and sealed ductwork will make your heating and cooling systems significantly more efficient. Energy loss is not the only concern. Duct systems can also involve the comfort of your family, employees, tenants, or customers, as well as your indoor air quality. Testing the ducts will locate leaks or damage and focus repair work in the right areas. A properly operating heating, ventilation, and air conditioning (HVAC) system will help reduce overall energy use—especially during hot summer days when air conditioners are working harder and putting a strain on the electric system—and will deliver greater comfort and cleaner air to every room (Ishii, 2002, pp.3111-3123).

In most residential and small commercial central heating and cooling systems, the conditioned (heated or cooled) air is delivered to each room through supply ducts and returned through the return duct to the furnace or air conditioner. The condition of both sections of this ductwork is vital to the overall efficiency of your heating and cooling system. What can go wrong? In some buildings, air escapes through poorly connected, disconnected, or deteriorated ducts, which can result in little conditioned air actually reaching your living or work space, leaving the area too warm or too cold. If the return duct system is leaky, it could be drawing in outside, stale, or polluted air and distributing it throughout the building; this air could come from an attic, a crawl space, or combustion air from a gas furnace, clothes dryer, stove, or water heater. If the supply duct system is leaking, the building can become depressurized, and air from outside may be drawn in to the ducting and distributed into the building. Either situation may decrease the quality of the indoor air. Research performed in the last 10 to 15 years has established these facts, and steadily increasing numbers of qualified HVAC contractors are learning how to eliminate duct leakage (Ishii, 2004, pp.779-801).

When to Test

Duct testing is strongly recommended when a new heating and/or air conditioning unit is being installed. If the existing duct system is leaky and inefficient before the new unit is installed, it will still be leaky and inefficient after the new unit is installed—unless the ducts are tested and sealed by a qualified contractor. It does not make sense to install a new, energy-efficient heating and/or air conditioning unit unless the duct system is also energy efficient. Duct testing is also recommended when a diagnostic tune-up is performed on a heating and air conditioning unit (Ishii, 2010, pp.96). A diagnostic tune-up can improve the operating efficiency of the heating or air conditioning unit itself, but the overall efficiency will still be less than adequate if the duct system is not in good condition. A duct test is necessary to determine leaks, needed repairs, ...