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.

Please advise,
Ron H.

Hi Ron,

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

Good luck,
Carl

Electric air-source heat pumps are the most popular type of heat pumps.

Electric air-source heat pumps have two main parts as shown in the illustration below:

The outdoor unit includes an outdoor heat exchanger (1), a compressor (2) and a fan.

The indoor unit contains an indoor heat exchanger (3) and a fan (4) that distributes warm or cool air to your duct system.

During the heating season, the outdoor unit collects heat from the outside air through the outdoor heat exchanger and pumps it to the indoor heat exchanger.
The heat is then distributed through the ducts in your home by the blower fan. A secondary heat source, typically a furnace, serves as a backup for days when temperatures drop below between 25 and 35 degrees.

In the summer, the heat pump operates like a regular air conditioner. It pumps heat out of your home and circulates cooler air to keep your home comfortable.

Because of cost and efficiency would it be a good idea to also use propane for heating?

Junior

Hi Junior,
Yes, that would be a good idea as it doesn’t appear that it ever gets too cold in Pine Ridge (see temperature graph below for Pine Ridge). Lucky you!

Whatever fuel amount (gas, elec., or oil) you use for heating will be minimal compared to what would be used in more frigid areas.

It doesn’t appear to get too hot in the summer either, so your air conditioning system won’t have to work too hard either.

The only other option you would have and one that I would explore is an air to air heat pump. Heat pumps in your area come very close to the cost efficiency of natural gas or propane. 

An air-source heat pump can provide efficient heating and cooling for your home, especially if you live in a warm climate. When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes.

Your local electric utility can figure operating costs for you for both systems, so that you can “crunch the numbers” and decide which is best.

Carl