Heating, Ventilation and Air Conditioning: The Respiratory System of Your Home
The heating and ventilation, and the air conditioning in a home is called the HVAC system. In newer construction, a lot of the HVAC duct work is tucked unobtrusively behind walls, floors, and ceilings. But in older homes, the components might be obvious — like a radiator or window air conditioner.
In general there are three energy sources that fuel heating and cooling systems:
* natural or propane gas is carried via underground lines into your home and into your gas fueled appliances like the furnace. Propane doesn’t come directly from a utility company; a storage tank for it is located on your property and underground lines carry it to the house.
* fuel oil is used to heat air, steam, or water to provide heat in the house. Gas and oil fumes can be noxious, so good ventilation is essential with these types of heating systems.
* electric furnaces and heat pumps are more commonly found in temperate climates. An electric furnace heats a house almost as if it were a giant toaster. A heat pump functions like an air conditioner in reverse. Electricity is used to power all refrigerated air-conditioning systems.
These systems need to be treated with respect. If your furnace goes on the fritz, do not poke and play around, trying to figure it out on your own. This equipment is best left to the professionals. Do, however learn how to shut down the system if you have to. Gas furnaces usually have a shutoff valve right in the gas line near the furnace, plus a main shutoff valve at the meter. Electric systems should have a switch. There will also be a dedicated, or single, breaker or fuse for that appliance in your home’s electrical system. There is usually a shutoff valve located near the bottom of a fuel oil tank.
Heating and cooling equipment is rated based on its efficiency. For furnaces, the acronym AFUE (annual fuel utilization efficiency) rates how efficiently the unit delivers warm air into the house. If you’re furnace has an AFUE of 78% which is the minimum by federal standards, it means that 78% of the heat the furnace produces actually gets into your home, and the other 22% goes up the flue. High-efficiency furnaces can deliver as much as 96%.
For cooling units, the acronym is SEER. The seasonal energy efficiency ratio follows the same idea: a higher number equates to better cooling efficiency. Recent federal law dictates that new central air-conditioning systems should have a SEER of at least 13. So if you need to buy a new HVAC system, don’t gamble with the inefficient stuff.
Hot water and steam heat
The operating principle behind hot water and steam heat systems is similar. A boiler heats water, which is then fed through pipes — as either steam or hot water — to radiators (or convectors) throughout the home. These systems can be durable! Boilers that are 80 years old or older are still chugging away, heating homes. An advantage to this type of heat is that the moisture content feels good to our bodies — especially when humidity levels can drop to zero during cold snaps.
Gravity furnaces
Warm air rises and cold air falls, and that’s the principle behind how a gravity furnace works. You’ll find them in homes built during the 1930s and 1940s and they are easy to identify — the furnace looks like a giant octopus. Tentacles extend every which way from a big, chunky, imposing belly, which is the heat exchanger. These furnaces aren’t manufactured anymore because they’re not very efficient.
Forced air
These common systems are affordable and flexible. As with most heating systems, the process begins with your thermostat. You set it to a desired temperature and the thermostat then calls down to the basement, “YOO-HOO! Mr. Furnace! The mistress of the house has called for 72Ã?°. Better get busy!” The furnace heats air in a chamber, which is then blown, or forced, into rooms through duct work and registers.
