HVAC Heat Load Calculator

HVAC Heat Load Calculator

Our HVAC Heat Load Calculator helps to estimate the heating and cooling requirements of a building to determine the most appropriate heating, ventilation and air-conditioning (HVAC) requirements based on the room dimensions, insulation type, outdoor climate, building occupancy, lighting, appliances and equipment, windows, and desired indoor temperature.

Select your unique variables and measurement system in our HVAC Heat Load Calculator below to quickly understand your heating and cooling requirements for your space.

HVAC Heat Load Calculation Formula

Our HVAC Heat Load Calculator considers a range of important variables, including the room’s size, the number of occupants, insulation levels, lighting, appliances, and windows. The heat load is measured in BTU/hr (British Thermal Units per Hour) for the Imperial system and Watts for the Metric system.

HVAC Heat Load Explanation

Room Volume

Multiply the length × width × height of the room to determine the total air volume inside the space and how much air needs to be heated or cooled.

Insulation Levels

Insulation determines how much heat escapes in winter and how much enters in summer. Well-insulated buildings will reduce the HVAC system workload. Our HVAC Heat Load Calculator provides different variables (poor, average, good, excellent) based on your buildings. Select a value that reflects the insulation properties of your building.

People in the Room

Room occupants or the number of people in the room can have a significant impact on heat load. The calculator uses an estimated value of 400 BTU/hr per person.

Heat from Lighting and Appliances

Electrical appliances and lighting generate heat. Heat load from these devices can be factored in by inputting their power consumption (Watts), which is converted to BTU/hr (for Imperial) or kept in Watts (for Metric).

Windows and Sunlight Exposure

Windows allow heat transfer depending on their size and orientation relative to sunlight. The calculator estimates heat gain or loss based on the total window area.

Measuring and cross-checking the above values before inputting them into our Heat Load Calculator helps to ensure accuracy.