Abstract: A forced air furnace comprises an enclosure, an adjusting mechanism, an interface, an electric heating element and a fan. The enclosure has an air inlet and an air outlet. The adjusting mechanism is operative to adjust the air outlet between an open position and a partially closed position. The interface is located proximate to the air outlet and is used to connect the air outlet to a duct. The fan is powered by an electric motor. Both the fan and the electric heating element are located inside the enclosure. There is also described a method of installing a forced air furnace. The method comprises the step of adjusting a size of an exhaust area of an air outlet of the forced air furnace in order to produce a desired exhaust airflow through the exhaust area when the forced air furnace is connected to a ductwork.