What Size HVAC Do I Need?

Do you own a commercial building that relies on an HVAC system for heating and air conditioning? Maybe you already have an HVAC system and you’re wondering if it’s the right size. Perhaps you’re looking to get a brand new system installed.

When it comes to HVAC systems, the size of your unit will impact how well your space can be heated and cooled. Generally speaking, the larger your space, the larger unit you’ll need. However, you also need to be equipped to handle the size unit you install.

Regardless of your situation, this article will help you identify the right size HVAC unit for your commercial building based on your specific needs.

What size HVAC do I need?

Commercial HVAC systems come in sizes that are suitable for a variety of spaces. To determine which size HVAC you need, you’ll want to consider these factors:

• How large is the building?
• How much insulation does your building have in the ceilings and walls?
• What is the average temperature difference between the outside and your ideal temperature inside?
• Where is the sun during the day? Is your building located in the shade or does it receive direct sun?
• What type of lighting do you have in each room? (LED? Halogen? Fluorescent?)
• What is the average size of each room?
• How many occupants are usually in each room?
• Does anyone cook or bathe in your rooms? For example, a health center with a hot tub or sauna?

Each of these factors will impact the way heat is retained throughout your building, so considering them will help you choose the right size HVAC system for your building.

The size of HVAC systems is measured in tons

Generally speaking, commercial HVAC systems range from 2-30 tons. To get an idea of the size, compare this range to the range of residential units, which are only 1.5-5 tons.

The larger the size in tons, the more heat/cool air the unit can produce to heat and cool your commercial space. However, you can’t just get the biggest unit and expect it to work. You need to calculate the correct size for your building based on your specifications, because running the wrong size system can be detrimental.

Why is commercial HVAC system sizing important?

You might be wondering why the size of your HVAC system matters. There are two reasons. First, an undersized unit won’t sufficiently heat or cool your space. It will have to work harder to cool your space, which will overwork the compressor and raise your electricity bill.

Second, an oversized unit will cost you more to operate and repair than what’s actually necessary. You’ll use too much electricity, which will be costly and a waste of energy. Also, if your unit is too big, you might not be able to control the humidity, which will make the space uncomfortable, not to mention support the growth of mold.

Choosing your cooling system

With so many options to choose from, how do you select the right size unit? To know which unit will suit your needs, you have to know a little bit about how HVAC units are sized and how much space each size can handle.

When it comes to the cooling side of a commercial HVAC system, a 1-ton system can remove about 12,000 BTUs of heat hourly. Generally speaking, it takes 20-25 BTUs to cool one square foot.

To know the exact heating and air conditioner capacity you need, you’ll have to calculate your building’s heating and cooling load. This will be affected by the average outside temperature, how your building is designed, where the sun hits the building, how fast heat is lost, and several other factors.

How to calculate HVAC size based on cooling needs

To figure out how many BTUs you need to cool your space, you can use this calculation:

1. Write down your building’s square footage.
2. Divide your square footage by 500.
3. Multiply your result by 12,000—this is your cooling load.
4. Add approximately 380 BTUs for every building occupant.
5. Add 1,200 BTUs for each kitchen in the building (or each room where heat is produced in excess).
6. Add 1,000 BTUs to compensate for heat absorbed through windows.
7. Divide your final number by 12,000. The result is the size HVAC system you need in tons to cool your space.

How to calculate HVAC size based on heating needs

Here’s a general idea of how many BTUs you’ll need in an HVAC system to heat a commercial building:

• 1,000-1,200 square feet: 21,000 BTUs per hour
• 1,200-1,400 square feet: 23,000 BTUs per hour
• 1,400-1,500 square feet: 24,000 BTUs per hour
• 1,500-2,000 square feet: 30,000 BTUs per hour
• 2,000-2,500 square feet: 34,000 BTUs per hour

This amounts to about 1 ton for every 5,000 square feet. For example, if your building is 40,000 square feet, you’ll need an 8-ton HVAC unit.

To pinpoint the right size, you’ll also need to calculate the approximate amount of heat loss during cold weather. Although, factors like occupants, lighting, and other activity in the building can compensate for some, but not all, heat loss. This calculation can be a little harder to perform if you aren’t used to the process.

A professional will help you get the right size HVAC system

If finding the right size HVAC system for your commercial building seems daunting—don’t worry—a professional can do it for you. When you hire a professional to check out your space, you don’t have to worry about messing up your calculations and ending up with the wrong size unit for your space.

Whether your current HVAC unit isn’t big enough or you need a new system installed, we can help. Our professionals can determine the right size unit for your space. We can install a new system, replace an existing system, or save you money by retrofitting your existing system with new features. We’ll even perform maintenance to keep your system in good shape for years to come.

Contact us today for more information.