CoolCalc uses design conditions specified in ACCA tables. It's important to note that heating and cooling design temperatures are not the most extreme temperatures that may occur in your area but rather the typical high/low temperatures that HVAC systems should be designed for in your area. ACCA design temperatures are updated approximately every 5 years.
Select the weather station that most accurately reflects the temperatures in your area. You may override the ACCA specified design temperatures only if local building code allows.
Heating Design Temperature – In the winter, the temperature should remain above this value 99% of the time.
Cooling Design Temperature – In the summer, the temperature should remain below this value 99% of the time.