There are many different types of furnaces used for heating the living areas of your home. For heat distribution you can have several different channels. First, there is the most common, "Forced Warm Air" (FWA). Heat is forced (supplied) into the home, by a blower fan, via a duct distribution system. The air then "returns" to the force through the ductwork. (Old furnaces have no fan and work off of the principle that heat rises. These big barrel type furnaces are called "Gravity" furnaces or "Octopus", for the way that the ductwork looks in the basement. These latter furnaces are extremely inefficient. The more efficient the duct system is, the better the heat will be transferred into the home. The second most common furnace is the "Hot Water Boiler". Water is heated in a tank (much like a Hot Water Heater), then it is distributed to the home via a water pump. (Some older systems work off of the gravity principle and have no pump. Again these are very inefficient.) Once the heated water reaches the living area, it is sent into the room through radiators. Some radiators are large and extend up to the bottom of the windows. Others are long and extend along the baseboards; From which they get their name "Baseboard Heaters". The third type of heat is "Steam". These furnaces work much like the Hot Water Boilers", except instead of heating water below the boiling point, they heat the water above the boiling point (212 deg.). Steam then rises through the pipes to heat the living area (when speaking of heat reaching just the living area via the pipes, this is not usually the case, for the pipes loss heat in the non-conditioned area and they need to be insulated. The fourth and most costly method is "Electric Radiant Heaters". Though these systems are 100% efficient, for all the heat reaches the living area, electric is the most costliest fuel. Other types of heat are "fireplaces", "pot-belly stoves", and "Heat Pumps" . Heat Pumps according to what part of the country you live in, can be placed at any point on this list. They are becoming more popular in new construction for they do not need a chimney for exhaust or any other fuel besides electric. Since they extract the heat from the outside's cool air (then pump it inside), they are limited by the outdoor's temperature. At a certain point they can no longer extract heat from the air (from 40 deg. on down), then secondary fuel systems start. The secondary fuel can be any of the above, but usually it is the most expensive, electric.
Fuels vary for heating and the type is usually dictated by the area you live in. Some people in remote areas can only use wood for fuel because other fuels cannot be transported to them. In most areas oil, kerosene and propane are available for they can be trucked to the homes and no pipelines from the distributors are needed. Natural gas is popular where available for once it is piped to the house, it's supply is constant.
All types of fuel have different fuel combustion procedures and burners. This is why there are so many different types of furnaces. Whenever a combustible fuel is used to product heat, the "efficiency" (and "safety") of the combustion process should be evaluated (for heat pumps, see the cooling section). This can be done with computerized equipment or manually using the proper combustion guidelines. Some sort of guidelines should be followed to do the job right, a visible inspection is not enough. The gases should be checked at all cleanings. The efficiency is on a scale from 1-100. At 100%, "all" the inputted fuel is turned into heat. If $100.00 is spent on fuel, $100.00 worth of heat will be given to the house ("if" the distribution system is 100% efficient). At 70% efficiency, if $100.00 goes in, $70.00 is transferred to the home, and $30.00 lost up the chimney. A 50% efficient furnace can cost a lot of money! With proper adjustments, furnaces can run at peak efficiency. There are common cleaning and tuning procedures that your furnace mechanics should be looking for when you have service. Oil and kerosene furnaces should be cleaned and inspected for safety yearly. Natural gas furnaces should be cleaned and inspected for safety every few years, depending on age. Heat Pumps should be checked when they no longer heat or cool properly. Since furnaces burn at such a high internal temperature (400-700 deg.), the metal heat exchangers that divide the combustion gases from the heated air can become stressed and crack. When this happens it can be deadly, for Carbon Monoxide from the combustion gases can be blown into the house. A furnace will usually last from 10-20 years and at these ages, routine safety checks are important.
Two other fuels that are available and not commonly used are "Geo-Thermal" and "Solar". We recommend these be used before other fuels for their sources, the earth and the sun, will not be depleted. "Geo-Thermal Heat Pumps"> extract the constant temperature of the ground soil or ground water and turn this into heating or cooling for the homes. "Solar Energy" collects the heat from the sun and then sends it into the home passively or actively. Passive systems work on the gravity or heat rising principle, or "thermal mass". Thermal mass is matter that can collect and store heat. Activesystems pump the heated air by way of a fan into the homes. Hot water can also be heated by the sun. This water can be used like a hot water heater or for heating the air. Also to be included in this list is "Wind Power" that creates electricity, and then can be turned into heat. Any heating system that relies on nature as its source for energy to heat transfer should be strongly looked into as an alternative or primary heating system. All combustible fuels produce Carbon Dioxide, which is leading to our severe "Global Climate Change". Electric Energy is one of the worst contributors to this, for it is produced many times by the burning of coal. With more efficient homes and heating and cooling systems, we can slow Climate Change.
The ways that homes are cooled is limited. The most popular is the "Window Air-Conditioners". Though these were once very inefficient, federal energy efficiency mandates have made these more efficient. These units cool only a small area and are fairly efficient because of this. Still the more efficient the building shell is, the better it will hold the cool air (see Home Weatherization). One important inexpensive measure you can do to a window that the unit is in is seal the crack between the two window sashes with foam. "Whole House Air-Conditioners" are usually the Heat Pumps method. Cooling is extracted outside in a condenser and then transferred indoors through a "freon" medium. The cool air is then forced into the house by way of the duct system. The more efficient the duct system, the more cool air you will receive. Since all air-conditioners run on electric fuel, which usually the highest cost fuel in all regions, it is to your advantage to make all areas of your home efficient, if you cool your home this way.
There are other ways to cool your home, but with the higher standard of living we are used to, they are seldom used if you can afford not too. "Window Fans" positioned to blow air out of the heated or sunny side of your house and pull cooler air from the northern or eastern side of the house work well up to a certain temperature. The more powerful the fan, the better it will work. "Whole House Fans", centrally positioned in the ceiling under the attic, work extremely well to cool the house to "a comfortable level" at high temperatures. They save a lot of money over their equals in comfort (which differs among people), "those being" most whole house and window air-conditioners. Whole house fans must be sealed in the winter and the attic must be able to let as much air out as goes in. From an energy saving and Climate Change stand point, the latter is the best way to cool your home, if you tolerate a higher comfort level to save money and the environment.
Cleaning and safety checking window units is not routinely done. Many people just buy new models when they go up. They can be services if you take them to qualified technicians. This saves money and natural resources. The filters should be cleaned regularly during the cooling season. Heat Pump Air-Conditioning Whole House units have numerous ways to service them. The best way though is to change the filter every three months. The coils should also be cleaned, and the freon checked for leaks (a major cause of the ozone depletion). The S.E.E.R. (Seasonal Energy Efficiency Rating) should also be taken during a check up. The higher the S.E.E.R., the lower your energy bills will be. A complete yearly check up should always be done. Oil and gas furnaces are the most likely candidates for this. The cost of this clean-and-tune will pay itself back quickly. A dirty, sooty oil furnace waste heat and an overfired gas furnace produces carbon monoxide and waste energy. A blocked chimney on any combustion unit can kill and drafts should be checked yearly. This is an investment that can save the life of you and your family!