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What Size Furnace Do I Need? 6 Factors & Tips

How Does a Furnace Work? 4 Main Components & AFUE RatingsA furnace is an important component of a comfortable, functioning house. It keeps you warm in the cold winter months and helps provide the ideal temperature for your home. There are many variables that will determine the correct size furnace you will need for your home. Factors to consider include gas or electric models, brand, and size. While you might be more preoccupied with brand and type, the size of your furnace is just as important. Buying a furnace that is too small or too large could disrupt your home and prove inefficient. To help you choose a correct capacity for your home, we have compiled a list of 6 factors that will impact the size of your furnace.

Factors That Affect Furnace Size

Here are the top 6 factors to consider when shopping for a furnace:

How Old Your Home Is

An old house will require a furnace with a higher British Thermal Units (BTU) rating when compared to a new home. Since old houses are assembled with less insulation than new households, you will need to purchase a furnace with a higher capacity to maintain a comfortable temperature in each room.

Insulation Quality

Similarly, if your home is not properly insulated, then you will need a furnace with higher BTUs.

WindowsNumber and Quality of Windows

Old, drafty windows may allow heat to escape from the interior of your home. This will force your furnace to work harder. If you have a large number of windows facing the south, they will heat your home passively and retain the house’s warmth, allowing you to purchase a furnace with a lower BTU rating.

Location of Your Home

One of the major factors that affect the correct size furnace you will need is the geographical location of your home. For instance, if you live in the Northern states, like Minnesota or Illinois, you will use your furnace much more than individuals that live in California or Florida. There are five main climate zones in the U.S. that will help you determine the furnace size you need. Zone 1 includes the southern regions, spanning from Texas to Florida. If you own a home in this region, you will need to purchase a furnace that is designed to provide 30 to 35 BTUs per square foot.

On the other hand, a homeowner that lives in Zone 2 will require a furnace that can produce 35 to 40 BTUs per square foot. Zone 3 (40-45 BTUs) features the states directly above Zone 2, including Kansas, Missouri, and Kentucky. Residents in Zone 3 will need to install a furnace that is engineered to provide 40 to 45 BTUs per square foot. Zone 4 lies in the middle of the US and includes states like Nebraska and parts of Utah and Colorado. The Zone 4 BTU range varies from 45 to 50 BTUs per square foot. Finally, Zone 5 covers a majority of the northern strip of states on top of the U.S. and requires 50 to 60 BTUs per square foot. To accurately see which zone your home lies in, look at a furnace sizing calculator.

HouseSize of Your Home

If you have a large home, you will need a more powerful furnace to heat up your home. The more square feet, the more BTUs you’ll end up needing.

Energy Efficiency Rating

The higher the energy rating, the lower your energy bills. Choosing the right furnace means getting the one with the highest energy rating within your budget.

How To Buy The Right Size Furnace

The first thing you will need to be familiar with when you are purchasing a new furnace is the metric British Thermal Units (BTU). This metric is utilized to measure the total amount of heat energy a heating system produces. Essentially, British Thermal Units is the heat output. An average furnace features a BTU rating that varies from 60,000 to 100,000. When people say “furnace size” they are typically referring to the amount of BTUs.

The two main things you need to look at prior to determining a correct furnace size for the square footage of your house is the BTU rating and efficiency score. To maintain a warm temperature in your home, you will need to invest in an energy-efficient furnace that will provide you with 40 to 45 BTUs of heat energy per square foot. In addition, choose a furnace with the highest energy-efficiency rating in your price range.

HomeSigns Your Furnace Is Too Small

If you purchase a furnace that is too small, it will not heat your house adequately. You will need space heaters and tons of blankets to compensate for the minimal amount of heat produced by your furnace. Additionally, a small furnace means that it will be running more often in an attempt to warm your house, driving up your bills and possibly causing more strain on your furnace. This could lead to more maintenance and repair bills in the future.

Signs Your Furnace Is Too Big

If you invest in a furnace size that is too big for your home, you might encounter problems like overheating. A large furnace in a smaller home means that it will be using more energy than it needs to, thus wasting your money. Because a large furnace will try to keep your home at the thermostat’s temperature, it will turn on and off more often. This can cause damage and deterioration in the long run.

Heating & Furnace Repair Services

Have any furnace questions or concerns? ServiceMark can take care of it. For over 60 years, we have been providing local families with trusted furnace repair services. From installations and replacements to maintenance and repair, ServiceMark does it all. In addition, we offer other types of HVAC and plumbing services such as air conditioning repair, drain clearing, and water heater installation. Don’t get stuck in the cold—give us a call for anything furnace-related! Give our team of technicians a call at (302) 367-7915 to schedule an appointment.

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