We have plans for a home that has 3124 s/f on one level. The home will be constructed with 20% stone and 80% Portland stucco. Two builders recommended two HVAC systems be used while one builder said that I only needed one. The home will be built in central Georgia.
3124 sq ft is a large house…too big for one HVAC system, especially in a one level house.
With only one system some of the air duct “runs” would be too long.
The HVAC system would have to move so much air to those “far corners” of the house that air noise would be very loud inside the house, and the system would be grossly inefficient.
The same would be true for the same size 2 story home…read my “Home Cooling and Saving Energy“.
And, due to this inefficiency, the one HVAC system will cycle” more frequently. This frequent “on/off” cycling, will make your house go through erratic temperature swings that will drive you nuts trying to adjust the thermostat to compensate for these erratic temperature swings.
Two smaller HVAC systems will not only be more energy efficient (money saving:)), they will be quieter, and keep your house more comfortable.
Also, with two systems, you could divide the house into comfort zones based on your needs.
You could actually shut one zone down from time to time to save energy if no one is using that area of the house at the time.
Net cost difference between one large HVAC system vs. two small HVAC systems? Not much considering the “trade off” of comfort and energy efficiency and of course, operating costs.
Here’s what ENERGY STAR has to say:
“Installing the right size equipment for the home is essential to getting the best performance and comfort. Many homeowners believe that bigger is better when buying new heating and cooling equipment.
But in reality, a system that’s too large will not keep your home comfortable because of frequent ‘on/off’ cycling. Incorrect sizing can also put stress on system components and shorten the equipment’s life.
To ensure proper sizing your contractor should provide a copy of the home’s heat gain/loss calculations for your records.” Source: http://www.energystar.gov/index.cfm?c=heat_cool.pr_hvac
Ron, a good heating and air conditioning contractor knows all this. Sound like you are talking to at least two home builders that use savvy HVAC contractors