What Size Furnace Do I Need?

Your furnace helps maintain the internal temperature of your home for comfortable living. When buying a new furnace, one of the most common questions that linger in the mind of buyers is what is the right size for their home?

The importance of using the right size furnace cannot be emphasized enough. While a furnace that is too small will fail to heat your home, an oversized furnace will overheat your spaces causing discomfort.

To figure out the right size furnace for your home, our contractor would need the Manual J Load Calculation report for your residence. This calculation gives contractors the exact furnace size in British Thermal Units or BTUs. A Manual J Calculation report is usually prepared by an energy auditor (after conducting an energy audit). An energy audit can cost you $250 or more.

BTU Explained

British Thermal Units or BTU is a unit of heat. It is used for measuring the quantity of heat output of a heating system. An average furnace falls in the 80,000 to 100,000 range. The higher your furnace’s BTU the more heat it can produce.

Another important factor to consider when buying a furnace is its efficiency. If you buy a 90 percent efficient furnace that delivers 90,000 BTUs of heat, the actual heat delivered by the system will be 81,000 BTUs, the remaining 10 percent will be lost through the flue.

Calculate the Square Footage of Your Home

To determine the right size furnace for your home, you need to calculate your square footage. For many homeowners, this is a relatively simple task. All they need to do is look up their home’s square footage from their lease, appraisal, or listing.

If, however, you cannot find information related to your home’s square footage, you will have to manually measure different areas of your home. Avoid measuring areas that do not have a duct.

Calculate the Required BTU Output

Once you have calculated the square footage of your home, multiply it with Virginia’s heating climate zone BTU requirements (45-50 BTUs/sq. ft.).

Let’s suppose your home’s square footage is 2,000 square feet. The total number of BTUs of heat you require is 2,000X45-50 BTUs/sq.f.t.= 90,000-100,000 BTUs.

Some Other Factors to Consider When Sizing a Furnace

• The number of windows in your home: The more the number of windows, the greater the heat loss.
• The number of floors: If you live in a two-storeyed, you may require fewer BTUs as the second floor will help insulate your home.
• Your home’s age: If you live in a new home, you may require fewer BTUs as new constructions usually lose less heat

Still can’t figure out the right size furnace for your home? Let AVS Heating and Air Conditioning help. We know a thing or two about furnaces. Our experts are committed to helping families make informed purchase decisions. To discuss your heating and cooling needs with an expert, call (703) 873-7484.