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The Importance Of Correctly Sizing HVAC Systems

We know how intimidating it can be as a first-time homeowner. There are so many technicalities to deal with and not everybody is well versed in the language of appliances. Well, we’re going to help lighten the load a bit by giving you all the information you need about correctly sizing your HVAC system. 

If you’re wondering what an HVAC system is, look no further, HVAC stands for Heating, Ventilation and Air conditioning. They are built into your home’s central air unit. It encompasses all your heating and cooling needs. They help maintain a comfortable temperature in your home. Basically, they keep you cool during the summer, help filter out any allergens, provide clean fresh air and during the winter, they help you stay warm.

You may be wondering why sizing is so important. It’s just a simple system so why does so much planning go into it. Well, incorrectly sizing your unit could have detrimental effects on your HVAC system, energy costs and the overall atmosphere of your home. 

Let’s consider the disadvantages of an oversized and undersized HVAC system. Undersized units usually aren’t as common as their oversized counterparts, but they could also have negative effects on your home or building.

  1. They have difficulties circulating air indoors.
  2. They have short cycles frequently: This is when the system turns on and off constantly. This is a very common sign of oversized HVAC units like furnaces or air conditioners. 
  3. More frequent breakdowns: Due to the constant short cycling, and the system turning on and off frequently it leads to strain on the components and their parts. Not only is this expensive to constantly repair but it is also an annoying inconvenience, especially if your unit breaks down at critical times when they’re needed most.
  4. Raises utility bills: Due to problems with air circulation, short cycling, and other problems the system has to work extra hard to maintain the desired temperature in your home. This will drastically increase energy costs and lead to higher bills. This is very common with undersized HVAC units, due to their inability to correctly maintain desired temperatures, there is extra energy required to carry out their functions.
  5. Reduced Life Span: The average life span of an HVAC system is 15-20 years. However, this can be significantly reduced if you get an incorrectly sized system. So, you won’t be able to use your HVAC unit to its fullest potential. 
  6. Temperature Inconsistencies: Due to short cycling, heating or cooling may not be very consistent. So, there may be some areas in our home that have hot or cold regions.
  7. Poor air quality and Excess Humidity: Incorrectly sized HVAC systems have difficulties removing moisture from the air because they don’t run long enough to do that. Thereby, there is an increase in air humidity which will not only negatively affect the air quality in your home, damage furniture and electronics but can also breed bacteria, fungi/mold and some viruses which could be detrimental to your health.
  8. Noisy Units: A properly sized unit will make little to no noise, but due to constant short cycling and wear and tear of engine motors, your HVAC system may be very noisy and disrupt your daily life and businesses. 
  9. Oversized units are expensive to purchase and install. Now add the cost of all the maintenance and repair work and it all just seems like a waste of money. 
  10. Undersized units require more fan power to work and are at risk of leakages in the ducts due to high pressure in the ducts.


So, you’ve decided to get an HVAC unit, but you’re confused about what size to get. Let’s help you out with that. Now that we have realized how choosing the wrong sized HVAC unit could prove detrimental to our health, possessions, comfort and even our bank accounts, let’s try and find an effective way to choose the right HVAC system for you. Some contractors will suggest you an HVAC system based on what other clients with similar homes to you have. This is not the correct way to choose an HVAC system.

There are 2 main ways you can use to determine the system size that is right for your home or building.

Firstly, determine the square footage of your home. You can do this by using a tape measurer to measure the length and width of the room. Multiply the length and width and this will determine the square footage of the room. Repeat this process for all the rooms and halls in your house and add these all together.

Secondly, determine the base BTU of your home. BTU stands for British Thermal Unit; it is the unit for measuring the energy that is used for cooling and heating. Multiply your total square footage by 25 because 25 BTUs is approximately the amount of energy needed to cool a square foot of a room.

Read also Explore Our AC Unit BTU Chart >>>

It is important to take into account your ceilings, if your ceiling is higher than 8 feet multiply your base BTU amount by 25% or 1.25.

The second method is usually carried out by licensed specialists. It is the Manual J or Manual D method. It is a technique to determine HVAC sizing. First of all, what is HVAC Sizing? It involves specific calculations done by a licensed contractor to determine what system will best fit your temperature and ventilation needs. The technician will take into account different factors such as the square footage of your home, the shape of your home, numbers of windows and doors, lighting, number of occupants, insulation, climate, home appliances and other factors

Choosing the right size for your HVAC system may appear like a stressful task and it seems like it would be easier to opt for any old thing you see. However, an incorrect choice will gravely affect your daily routine and lead to may unnecessary money spent. The extra time you spent correctly choosing the right system for you will pay off in the long run. 


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