Load Calculation Rules of Thumb

At cfm we like rules of thumb. We have rules of thumb for airflow, air distribution, cooling capacities and more.

Today we provide you with a “Square Feet per Ton” cooling rule of thumb guide based on some common applications.

Note: your project or application may vary widely from the following. This is for informational purposes only.

Each rule of thumb is based on the following:

98/78 db/wb summer ambient design temperature
0 db/wb winter ambient design temperature
72 degF space temperature at 55% Rh
Windows: double pane with mix of shaded and unshaded
Insulation: R-10 walls, R-19 ceiling
Average lighting
Fresh air requirements from the 2018 IMC ventilation tables

Office space with 8′ ceilings

373 square feet per ton cooling
20 btuh per square foot heating
1.1 cfm per square foot
0.50 cooling tons per person

Retail sales floor with 14′ ceilings

321 square feet per ton cooling
34 btuh per square foot heating
1.2 cfm per square foot
0.20 cooling tons per person

Religious worship with 18′ ceilings*

115 square feet per ton cooling
75 btuh per square foot heating
3.9 cfm per square foot
0.08 cooling tons per person

Classrooms with 8′ ceilings

213 square feet per ton cooling
48 btuh per square foot heating
1.9 cfm per square foot
0.15 cooling tons per person

Restaurant dining room with 8′ ceilings*

132 square feet per ton cooling
73 btuh per square foot heating
3.1 cfm per square foot
0.11 cooling tons per person

Theater or multiuse assembly with 14′ ceilings*

107 square feet per ton cooling
85 btuh per square foot heating
3.7 cfm per square foot
0.10 cooling tons per person

*Design tip: on applications that approach 3+ cfm per square foot, it might make sense to add an ERV. In our next article we will explain why adding an ERV could be beneficial, how it affects air distribution, and if they make financial sense. Subscribe here to get a copy sent direct to your inbox!

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Brad Telker

Vice President of Sales, Applied Systems Group at cfm Distributors, Inc.

Brad was born and raised in St Louis Missouri, where he spent the first 18 years of his life. At the ripe young age of 18, he embarked onto his next big adventure, traveling to the University of Missouri Columbia for a bachelor’s degree in Mechanical Engineering. Brad joined the cfm team in 2006, and now as the Vice President of Commercial Sales, he focuses on business development, as well as helping contractors and engineers find creative and unique solutions to any size project. When he’s not at work, Brad enjoys photography, running and spending time with his family.

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