Heating

Compare the efficiencies of the several systems. Manufacturers and dealers generally use steady state efficiency—how well the furnace or heating unit performs once it is warmed up and running steadily, but this does not account for the fact that a furnace cycles on and off, and uses more fuel to repeatedly heat up the furnace itself. Seasonal heating efficiency does account for this. It is also known as the “Annual Fuel Utilization Efficiency” or AFUE.

1. Forced air systems are probably the most common. They consist of a furnace that heats the air, a fan which blows the hot air through a distribution system of ducts, and controls, chiefly the thermostats. Heat is provided quickly, and the ducts can be used for other purposes, such as humidification and cooling. On the other hand, ducts require maintenance to repair damage and to prevent leakage, both fans and ducts make some noise, and, in addition, it is difficult to have different temperatures in different areas of the house ( known as "zoning").

2. Baseboard radiators use a boiler, rather than a furnace, to heat circulating water. There is no fan to create noise, and there is less heat loss than with forced air because there are no ducts. Also there are no drafts, and zoned temperatures are easy to arrange. Furniture placement may be difficult as the baseboard heaters must be kept clear of obstructions. Pipes for the circulating water cannot be used for other purposes. Boilers are generally fueled by oil. Gas boilers are generally less efficient than gas furnaces; condensing is not feasible because the return water is too hot.

3. Hydronic radiant floor heating is usually considered the most comfortable heating system.
Hot water circulates through pipes mounted under the floor or embedded in concrete slabs. It is efficient because it heats at a lower temperature. Furniture placement is of no concern, although carpeting is not advised. It is an easy system to zone. When the system is turned on, it takes longer to reach the desired temperature, but in general the heat is steadier, without the fluctuations of other systems.

4. Direct source systems generate heat at the point of use. This category includes vented gas heaters, kerosene wall heaters, electric baseboard radiators, and wood-burning stoves. In general they are inexpensive to buy and to install, unless venting is required. (Unvented kerosene heaters are considered dangerous.) Zone heating is easy. In super-insulated houses, direct source heating may be cheaper than central heating. Direct source heaters are space hogs, however; they not only take up floor or wall space, but must not be blocked. They heat only a small space and have no ducts which can perform other functions, such as air conditioning.

5. Heat pumps deliver heat from one place to another rather than generating heat. Air source heat pumps are used for cooling as well as heating. They are not recommended, however, where temperatures often fall below 30ºF (- 1ºC). Ground-source and water-source heat pumps do not have such air temperature restrictions. Instead of drawing heat from the air, whose temperature fluctuates, they draw heat and cold from underground (below frost line) where temperature is constant. These types of heat pumps are not very good for small houses and they require a lot of land or a large body of water.