Disadvantages of a Warm-Air Heating System
One of the principal disadvantages of a gravity warm-air heating system is that the furnace must be centrally located at the lowest point in the structure. This, of course, severely limits the design flexibility of the structure itself. Other disadvantages of gravity warm-air heating systems include:
1. Slow response to heat demand from the thermostat
2. Slow air movement
3. Inadequate or nonexistent air filtering
Forced-warm-air heating systems depend upon blowers to circulate the air through a network of sheet-metal ducts. Both the operation of the blower and the expansion and contraction of the ducts as the air temperature rises or falls can cause distracting noise.
Warm-air outlets can frequently create decorating problems. In order to operate effectively, the registers should never be blocked by furniture or carpeting. This requirement, of course, restricts furniture arrangement and the placement of carpet.
The blower in a forced-warm-air heating system will create a certain amount of air turbulence. This rapid agitation of the air causes dust particles to circulate and deposit on walls, furniture, and other surfaces. Ordinary filters will remove most of the larger particles but are not very effective against smaller ones. An electronic air filter is recommended for the latter.
Warm-air heating systems require separate hot-water heaters to supply the hot water necessary for household use. This requirement for additional equipment adds to the initial installation costs for the system (in a hot-water heating system, the hot water for household use is supplied by the boiler).
Forced-warm-air heating systems supply convected heat through forced-air movement. The heat is supplied in bursts (rather than a continuous, sustained flow) when the room thermostat calls for it. This results in room temperatures varying up and down several degrees. The variation in temperature can be considerably reduced by setting the fan switch for continuous blower operation.