A Correct-Sized Furnace is Essential for Home Comfort and Energy Efficiency
The first rule for determining the correct gas furnace size for your home is to select a heating and air conditioning repair company that employs skilled technicians with the requisite experience to undertake this crucial job.
Modern furnace sizing requires detailed knowledge of how to match a furnace to a particular size and type of home, while considering numerous other factors. It’s a rare homeowner who’s equipped to do this, and unfortunately, not every HVAC contractor is either. Others may possess the skills but just don’t want to spend the time to do the job right.
The traditional way of estimating furnace size is considered outdated
Not so many years ago, your furnace installer might have used a “rule of thumb” calculation to determine what size furnace to place in your home, based on your square footage. They would then increase the recommended size “to be on the safe side” (and increase their take in the purchase transaction).
In recent years, as technology has improved by leaps and bounds and the HVAC industry has invested more in high-tech training, problems with the old approach have become apparent. Square footage is very important, of course, but it’s just one of many factors that go into figuring out what size heating or cooling system will best serve a home. More on that later.
Mis-sizing an HVAC system will produce a variety of problems.
- A furnace that’s too small will overwork itself to heat a home during winter weather, while
- an oversized furnace will create its own batch of negative issues.
- A furnace that’s too big may “short-cycle,” meaning it will run at full-go for a short period, stop when the thermostat temperature is quickly achieved, and repeat that process over and over again.
- This on-and-off, on-and-off operational mode will stress the equipment, waste energy (since more energy is expended when a furnace kicks on and ramps up), and not filter your indoor air as efficiently. It’s also very loud and obnoxious.
- Comfort in your home’s rooms and areas also will be negatively affected when the heating or cooling comes in short, quick cycles.
Dedicated software is essential for furnace sizing
In order to determine the correct-sized furnace, the best heating companies perform a heating load calculation on your home, using the industry-standard software, Manual J. The heating load is basically the amount of heat required to make a particular home comfortable.
Manual J takes into account the size and layout of your home, as well as a variety of other factors as suggested earlier in this blog. They include
- the number and type of windows,
- other heating sources in the home,
- the airtightness of the home,
- the quality of insulation,
- building materials in the home, and
- other factors.
Once the heating load calculation is complete, the technician will use the results to recommend the right size furnace for your home.
Almost as important as a furnace that’s just the right capacity for your home is ensuring that your home’s ductwork will be compatible with your new furnace.
An HVAC installation technician should inspect your home’s duct system and recommend improvements, repairs or even replacement before a new furnace is installed.
Other factors that better furnace installers take into account are what level of efficiency your furnace should have, and what advanced and complementary features should be installed along with it. This could include
- whole-house humidity control and/or air-cleaning,
- a variable-speed blower motor, and/or
- a state-of-the art thermostat for your system.
Every year, more advanced features become available, so make sure you ask your preferred Cincinnati HVAC partner about new technology.
The same rules apply to ACs and heat pumps
While this blog is about furnace and other heating system installation, most of the points apply equally to AC and heat pump selection and installation.
An incorrectly-sized cooling system will result in the same negative issues you’ll get with a bad furnace selection. In the case of an AC or heat pump purchase, a cooling load calculation should be made on your home.