Today, your choices of home air conditioning systems includes more high tech, variable speed furnaces and air handlers. These systems tend to run longer at lower blower speeds in an attempt to improve comfort and increase dehumidification. This is great when you have a well-designed tight, balanced duct system.
A single-speed furnace or air conditioner comes on full-blast no matter what. That may be okay in the dead of winter or heat of summer, but in the spring or fall, when outdoor air temperatures are less extreme, a single-speed unit may heat or cool rooms too quickly.
Besides this basic functionality on forced air HVAC systems, there are only about two real comfort feature options. The two features that can increase your comfort, though, are noteworthy and valuable. They are two-stage heating, and self-adjusting blower speeds. Both of these are available for forced air furnaces.(Remember, it's the blower system of your furnace that moves the cool air from the evaporator through your duct systems.)
The benefits of a two-stage furnace with variable speed blower are that it makes you more comfortable due to more even temperatures throughout the home, maintains a more steady
temperature (keeps the house at nearly the exact temperature you set your thermostat), increases your air conditioning efficiency about 8% (if you have air conditioning), has a lower operating cost (due to a DC voltage variable blower motor), increases efficiency of any attached air cleaner, and is quieter than other furnaces. The benefits of a two-stage furnace with multi-speed blower
are similar to the Two-Stage Variable Speed models. However the Two-Stage Variable Speed models are even more quiet, even more electrically efficient, and even more comfortable.
Richard Rue, an energy efficiency building expert, whose engineering firm has engineered over 42,534 Ultra Energy Efficient homes tells his clients this:
“Variable-speed equipment can ramp down from a 5-ton unit, for example, to as little as a 1 1/2 tons; this will help control moisture in a house much better because the unit will operate at a lower speed and run longer to control humidity. Keeping humidity levels below 50 percent creates an environment where even dust mites and mold spores can’t grow.”
Another reason why replacing your home air conditioning system is not the same as swapping a new refrigerator for your old one.