How to Properly Size HVAC for Commercial Buildings
Climate change is affecting summer and winter weather, and it can be challenging for older HVAC systems to keep up with extreme temperature fluctuations. Keeping commercial buildings comfortable, especially in populated cities that might be prone to the urban heat island effect, will become more challenging moving forward. Installing an upgraded, energy-efficient HVAC system is one potential solution, as long as the unit is properly sized.
Here’s how to choose a properly sized HVAC system for a commercial building.
Understanding HVAC Ratings
Choosing a properly sized HVAC system starts with understanding how these devices are rated. The heat an HVAC system can remove is measured in British thermal units (BTUs). An air conditioner is rated in tons, ranging from small half-ton machines to 30 tons and up for large commercial spaces.
Bigger isn’t always better. Selecting an HVAC unit that’s too large for a given area will waste energy and cost more in the long run. Integrating the device seamlessly into the space isn’t as important in commercial designs as in residential ones. Still, you may also wish to consider the aesthetics of the installation. Choosing the correct HVAC unit requires more calculations, especially for businesses.
Calculating the Approximate Size
Determining the ideal HVAC system size starts with the square footage of the space you’re trying to cool. This calculation is designed for buildings with standard 8-foot ceilings. If yours is taller or you have vaulted architecture, you’ll need to adjust your estimates accordingly. For argument’s sake, we will use a 12,000-square-foot office building as an example.
Once you have the total square footage for the entire building or the space you’re trying to cool, divide that number by 500. Using our example building leaves us with 12,000/500 = 24. Next, multiply that number by 12,000, determining how many BTUs you’ll need to cool the space before considering any other variables. This structure will need 288,000 BTUs for effective cooling.
Finally, you need to consider variables that can impact the heat level within the building. Each person adds approximately 380 BTU. Windows add 1,000 BTU and kitchens can add up to 1,200. If our example office houses 50 employees on average, has 20 windows, and a single kitchen in the break room, that adds 40,200 BTU. That brings the total to 328,200 BTU we need to compensate for when cooling the space.
Converting BTUs to Tons
Cooling is measured in BTU, but HVAC units are rated in tons, so there’s one more math problem to solve before determining what kind of HVAC unit will work best for our hypothetical office space. Divide the total BTU by 12,000 again to determine the tonnage necessary to cool the area. For our theoretical office, 328,200 BTU converts to 273.5 tons, and it will require multiple AC units. Commercial units are available up to 25 tons, and anything larger than that is considered industrial.
Multiple rooftop AC units aren’t unheard of for large commercial structures. The 12,000-foot office will need a minimum of 11 25-ton HVAC units or a lower number of larger ones. The number and size will depend on the specifications of the building and how much additional weight the roof can safely support.
Powering the New HVAC System
The cooling power of an HVAC unit isn’t the only thing you’ll need to calculate when installing a new system. Depending on how the building is used, you may also need to install a transformer to ensure energy is delivered safely and correctly to the structure.
Commercial buildings often come equipped with additional low-voltage transformers to support individual systems. Plug loads and HVAC units may need their own, depending on the size of the structure. Understanding the size of the transformer you require will depend on the building’s power needs.
Opting for Energy Efficiency
Consumers looking for new HVAC units or other appliances for their homes have the Energy Star guidelines to look to. Large commercial and industrial HVAC units larger than 240,000 BTU per hour or 20 tons aren’t subject to Energy Star requirements. However, they may still offer energy-efficient options to help businesses and building owners reduce their energy use and shrink their carbon footprint.
Adding other features, such as AI, insulation, and double-pane windows to prevent heat loss, can also help improve the structure’s energy efficiency.
Keeping Things Cool With a Properly Sized HVAC System
Keeping large commercial spaces cool might seem more complicated than doing the same for small residential buildings, but most of the science is the same. Calculate the necessary BTUs for cooling based on the square footage. Don’t forget to incorporate data about the number of windows and kitchens in the space and the average number of employees working within its walls.
Doing the math ahead of time will ensure you install the correct HVAC unit for your commercial property and keep everyone comfortable while at work.
Author: Emily J. Newton is the Editor-in-Chief of Revolutionized. She is a journalist who covers the innovations impacting the construction and industrial sectors.
