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Do You Count the Basement When Sizing a Furnace?

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Your heating system keeps you warm when the weather turns cold. A properly sized furnace is crucial to warm your entire home. But do you count the basement when sizing a furnace? 

Our HVAC technicians at S&L Air Conditioning and Heating answer that question in detail. We offer furnace installation in Bowie, MD, and can help you size a furnace for your home.

Let us help you figure out exactly what size furnace you need and how to get it installed, with upfront pricing and a written guarantee.

Do You Count the Basement When Sizing a Furnace?

When sizing your furnace, you need to count all the square footage of rooms you want to heat. If you want to heat your basement, count it when sizing your furnace.

If you have an unfinished basement, including it depends on whether you plan to finish it. If you’ve already got a finished basement, you should include that square footage in your size estimate.

It’s possible a split system that offers zoned heating would work best for you, so talk to the HVAC experts to determine the best course of action for your home and choose a furnace that’s the right size.

Factors to Consider When Sizing a Furnace

Whether you want to heat your basement or not, you should take several factors into account when sizing your furnace.

Climate and Sun Exposure

It stands to reason that homes in colder climates would require larger furnaces—but how much larger depends on square feet, not the BTUs or price of the furnaces you’re looking at. If your furnace is too small, your indoor temperature might drop in the winter. Too big, and you’re wasting money and endangering your ducts.

We measure furnace power in BTUs, which stands for “British Thermal Units.” You may also have seen HVAC systems described in terms of tons. An HVAC “ton” refers to the heat necessary to melt one ton of ice, and it’s equal to 12,000 BTU. So a 1,600-square-foot home requires 72,000 BTU, which would be a six-ton furnace.

Your home’s climate is important when sizing your furnace. In fact, there are laws in place to ensure that furnaces match the probable temperatures you’ll experience. For example, Maryland sees 2,400 to 3,000 sunshine hours a year, so you don’t need a particularly large furnace as you might in a snowy area of Montana.

Square Footage

If you don’t know your home’s square footages offhand and don’t have blueprints to check, the easiest way to figure it out is by measuring each room on every floor that you want to heat—and even those you don’t, if there’s a chance of cold bleeding through doorframes or windows.

Length times width equals area, measured in feet, with extra feet to account for above-average ceiling height. You add up the square footage of every room, and that’s the total square footage you’re working with.

Next, try these averages for a good starting point for the size of furnace you should be looking for:

  • 1,000-1,200 square feet: 45,000-54,000 BTU
  • 1,300-1,500 square feet: 59,000-68,000 BTU
  • 1,600-1,800 square feet: 72,000-81,000 BTU
  • 1,900-2,100 square feet: 86,000-95,000 BTU
  • 2,500-3,000 square feet: 113,000-135,000 BTU

Your Insulation Situation

Next, you’ll need to evaluate the condition of your insulation: Was it installed recently? 

Homes with average or poor insulation require more powerful, larger furnaces than homes with good insulation:

  • Good insulation: For the best energy efficiency and furnace performance, you’ll need a house wrap like Tyvek, attic insulation, and energy-efficient doors and windows. 
  • Average insulation: If your home hasn’t been updated for energy efficiency but was built after 1990, your insulation is most likely in average condition.
  • Poor insulation: If you haven’t updated your home’s insulation for the past 30 years and you notice drafts or gaps around your windows and doors, you may have poor insulation. 

How Long Does a Furnace Last?

The average lifespan of a furnace is 15 to 25 years. You can add five years to that with regular maintenance, which means not just paying attention to the possible danger signs but having it inspected and serviced regularly.

Get in Touch for Help Sizing a Furnace for Your Home

Do you count the basement when sizing a furnace? The answer is yes. At S&L Air Conditioning and Heating, our HVAC technicians can help you size your home and choose the right furnace. Whatever your heating needs, we’re here to help. For the best in furnace repair or installation, call S&L Air Conditioning and Heating at (301) 690-0484.

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