Forced Air Heating

Heat Transfer

All forms of heating work on three basic modes of heat transfer: Convection, Conduction, Radiant.

Convection Heat Transfer is the most familiar type of heat. All forced-air systems are convective heat transfer systems. This includes hydronic baseboards and fan coils.

Conductive Heat Transfer is energy moving through an object. Place a metal pot on the stove and in a few minutes the handle is hot.

Radiant Heat is the most comfortable and efficient form of home heating. Radiant floor heating systems conduct heat through the floor which then broadcasts heat to every cold object in the room, especially to you.

Forced Air Heating

A forced-air heating system draws room air through ductwork and a filter into a furnace, where the air is heated. The warmed air is then blown through the ductwork to vents throughout the house.

One of the benefits of a forced-air system is that it can include an air-conditioning unit, a humidifier, and an air filter--and all of these can take advantage of the system's ducts for delivery of conditioned air to rooms.

Here's how the typical forced-air system works:

With a forced-air system, a blower draws cool air in from rooms through ductwork. Inside the furnace, the air passes through a filter into a heat exchanger where the burner heats it, then it's blown back to rooms through ducts and registers.

The thermostat signals furnace to turn on when air temperature dips below a set level. When this happens, a gas valve regulates and delivers fuel to burners and-if there is one-the pilot light. The burner is ignited inside combustion chamber, creating heat that is transferred to the heat exchanger. Combustion fumes are vented out through a flue out the rooftop or, with high-efficiency models, through the wall.