Bellevue HVAC Load and Air Balance

Frustrated that you do not have control of your space’s (office, room, etc.) temperature? If you shiver through the summer months and are equally uncomfortable in winter, chances are your office’s HVAC system may need to be balanced. For a system to be properly balanced, load must be considered. Bellevue HVAC Service & Repair can perform a load calculation and assure that your system’s air flow is balanced to achieve peak performance and maximum comfort.

Cooling/Heating Loads

To effectively calculate the cooling/heating load for a conditioned space, you must take into consideration both external and internal loads.

External Loads

As the moniker indicates, external loads are factors outside that affect heating/cooling of a conditioned space:

  • Air Temperature
  • Sun Loads

Keep in mind that external loads only affect spaces in a building that have external walls (along the perimeter). Additionally, as external loads are not only weather related, they are also time-of-day sensitive. As such, external loads are in a constant state of flux. 


Internal Loads

Essentially anything that produces heat or uses electricity is part of the internal load equation:

  • Lighting: overhead and task
  • Office Equipment: copiers; computers; phones; fax machines, etc.
  • Kitchen Appliances: refrigerator; coffee pot; stove; microwave, etc.
  • People
Even internal loads vary somewhat throughout the day. As more employees are at their desks at 9:00 AM than at 12:00 PM, the load will be greater in the earlier morning from internal loads, but likely higher from external loads. 

Now What?

The best any Bellevue HVAC Designer can hope for is that each tenant is equally comfortable with regards to temperature and humidity throughout the day. In a perfect work environment, each space or area has its own thermostat. The fact of the matter is, however, often thermal zones are decreased to save cost on construction. In either case, the theories remain constant.

During building design, it is essential that each floor of an office space have at least 5 thermal zones:

  1. North
  2. South
  3. East
  4. West
  5. Interior Space
Ideally, each space (office, room, etc.) would be its own thermal zone. Not likely! Rather, thermal zones are determined as to type of space. For example: the kitchen, which has a high thermal load will not be zoned with an inside office space with a low thermal load. Also, external thermal zones should also be divided according to each spaces direction (N, S, E, W, internal).

To simplify the concept, consider an internal office with 1-occupant.  As there are no external loads, the total load would be from the occupant’s body heat and any office equipment within the space. If the thermostat is not in this particular office, the theory is that every space within a given thermal zone will experience the same (approximately) load changes throughout the day. Additionally, every space within a thermal zone should have similar attributes and loads.

Air Balance

The balance of airflow within an HVAC system essentially determines the amount of conditioned (heat/cold) air that flows into a given thermal zone. While you may be tempted to tape a piece of cardboard over the vent in your office – this is not the most effective solution. It is best for the building engineer, or for Bellevue HVAC to properly balance the load with damper(s) especially for this purpose.