Cooling Load Calculation Procedure


Obtain Building Characteristics

  1. Construction materials.
  2. Construction material properties: U-values, R-values, shading coefficients, solar heat gain coefficients.
  3. Size.
  4. Color.
  5. Shape.
  6. Location.
  7. Orientation, N, S, E, W, NE, SE, SW, NW, etc.
  8. External/internal shading.
  9. Occupancy type and time of day.

Select Outdoor Design Weather Conditions

  1. Temperature.
  2. Wind direction and speed.
  3. Conditions in selecting outdoor design weather conditions:
  • Type of structure, heavy, medium, or light.
  • Is structure insulated? If the structure is heated or cooled, the structure must be insulated by code.
  • Is structure exposed to high winds?
  • Infiltration or ventilation load.
  • Amount of glass.
  • Time of building occupancy.
  • Type of building occupancy.
  • Length of reduced indoor temperature.
  • What is daily temperature range, minimum/maximum?
  • Are there significant variations from ASHRAE weather data?
  • What type of heating devices will be used?
  • Expected cost of fuel.

Select the indoor design temperature to be maintained in each space.

  • Estimate temperatures in unconditioned spaces.
  • Select and/or compute U-values for walls, roof, windows, doors, partitions, etc.
  • Determine the area of walls, windows, floors, doors,  partitions, etc.
  • Compute the conduction heat gains for all walls, windows, floors, doors, partitions, skylights, etc.
  • Compute the solar heat gains for all walls, windows, floors, doors, partitions, skylights, etc.
  • Infiltration heat gains are generally ignored unless space temperature and humidity tolerance are critical.
  • Compute the ventilation heat gain required.
  • Compute the internal heat gains from lights, people, and equipment.
  • Compute the sum of all heat gains indicated in items G, H, I, J, and K earlier in this list.
  • Include morning cool-down for buildings with intermittent use and night setup.
  • Take into account excess HVAC system capacity permitted for morning cool-down.
  • Consider equipment and materials that will be brought into the building above the inside design temperature.
  • Cooling load calculations should be conducted using industry-accepted methods to determine the actual cooling load requirements.

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