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Keystone Homes - man adjusting thermostat

Between picking the right AC units, double pane windows and testing the right ventilation system, building energy efficient homes is no easy task. Paying attention to the details can be the difference between paying a small fortune for a sticky house or comfortably smiling at your wallet each month. At Keystone Homes, we strive to save you money on your energy bills through energy usage and our HVAC units we install.

First, we use Tempstar units, a brand manufactured by Carrier, for all of our homes. We used to use other vendors but had issues of the recall variety, so we switched on the recommendation of our heating and air partners, Southern Mechanical. We’ve been using Tempstar for probably 7 or 8 years, and they have been reliable.

The units are 14 SEER (seasonal energy efficiency rating). Our two-story homes have separate thermostats upstairs and downstairs, so you can control the temperature separately based on your preference. Our large two stories, over about 2700 or 2800 square feet, have two separate units. Homes that are less than 2700-ish square feet receive one unit with a damper system, so the air is sent to the right floor, depending on the needs of the thermostat.

We do a manual D and a manual J load calculation before we ever build a home. This looks at the properties of the home to determine the best layout for the system, down to CFM output to each room, based on the heated and cooled volume of the home, direction the home is facing, number of windows, insulation specs, etc.

These calculations are important to make sure that the unit is sized correctly. Finding a good balance between sizing a unit large enough, that isn’t too large, is pivotal. If we put too large of a unit in, it would cool and heat the home too quickly, and wouldn’t have enough “up-time” to condition the air in the home. If this happened, the unit wouldn’t have a chance to pull the moist air out of the home, and you would be left with humid air, which bugs and mold love. Our goal is to make sure our HVAC units are sized just large enough to keep up with demand so that they won’t over-cool or over-heat the home.

Our homes are energy efficient, so less of a load is placed on the heating and cooling system.

HERS Ratings

As for energy efficiency, I have the feeling that you are a numbers person. Talking about energy efficient practices is good, but data tells the real story. Are you familiar with HERS ratings? HERS stands for Home Energy Rating Score. Basically, it’s a measure of energy efficiency and calculated using the specs of the home and tested with a blower door and duct blast test. A HERS rating of 100 is the rating a new, to-code home would have. Lower is better. Higher is worse. A home with a HERS rating of 110 would be 10% more expensive to heat and cool than a home with a HERS rating of 100. So, here’s where I get to brag about our numbers a bit.

According to Georgia Power’s data from Keystone in 2018, our homes averaged a HERS rating of 68. So, according to Georgia Power’s numbers, a to-code new construction home with a HERS rating of 100 would cost 47% (100 SEER / 68 SEER = 1.47, or 147%) more than a comparable Keystone home with a HERS rating of 68.

As an example, let’s say a power bill in a “to-code” home with a HERS rating of 100 that came in at $200. The energy cost of a 68 HERS home would have been $136, if all things were equal, saving $64.

According to Georgia Power, the average resale home in Georgia has, as a HERS rating of 140. So, the stats get even better when you compare us to the average resale, where we clock in at half the energy cost! At a HERS rating of 68 versus a resale HERS of 140, that $200 bill would be cut in half.

Think about where you would rather spend that $200 each month!

Whether you’re considering Keystone or another home builder, if you’re interested in knowing more about how we achieve this level of energy efficiency, please reach out to us. Our online sales counselor and all of our listing agents are knowledgeable about this subject and would be happy to help!

*As a disclaimer, these numbers were provided by Georgia Power, and the numbers I provided you here are assuming the accuracy of their calculations. We build our homes with the same energy specifications in both Georgia and South Carolina, so you’ll see similar results in South Carolina as you would in Georgia.*


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