There are four common types of heating units:
- A furnace provides heat through a forced-air distribution system.
- A boiler provides heat through a hydronic distribution system. (Hydronic systems are also referred to as hot water systems.)
- A space heater supplies heat directly to the room where it is located.
- A heat pump extracts heat from the air, ground and water outside the house and usually delivers it through a forced-air distribution system.
Most heating systems need air for combustion. Furnaces, boilers and space heaters that burn fuels need a supply of air to be able to burn properly, and a vent to the outdoors so that combustion gases can escape from the house. Electric heaters do not need to be vented. Combustion is a two-step process: air in, and gases out.Air InIn the past, there was usually plenty of air leaking into a house to keep the furnace, boiler or stove burning well. Modern homes, however, are better sealed and use controlled ventilation, rather than uncontrolled leakage, to provide greater comfort and energy efficiency. Vents that supply air for heating units should never be blocked. It is important to ensure that there is an adequate supply of combustion air available, even when other air exhausting equipment is in use.Gases OutVenting used to be done through a chimney. Today, however, many models of natural gas, oil and propane equipment can be vented by pipe directly through the wall, which greatly simplifies installation. Remember that combustion gases cannot escape from your home unless you provide air to replace them. That’s why venting problems can often be traced to air supply problems.