Air Balancing

An "air balance" is a process for measuring and adjusting the performance of an HVAC system in order to provide a comfortably conditioned/heated/ventilated home.

There are two procedures for air balancing: Comfort Balance and Certified Air Balance.

A Comfort Balance is simply checking to see whether the room feels comfortably conditioned. This involves walking room to room to see if sufficient air is coming out of the registers, and asking the occupants if they are comfortable. If they are not, adjusting/moving registers and/or installing restrictors/dampers after the fact to balance air flow may be all that is required. Many home owner complaints are specific to air circulation, too much and too little, and a simple comfort balance is all that is needed.

Certified Air Balance is at the other end of the spectrum. The purpose of this type is to insure all components of the HVAC (heating, ventilating, air conditioning) system are working in harmony, at optimum performance and providing total home comfort.

First a set of mechanical drawings are generated from a mix of occupant desires, local codes, and ASHRAE standards. The correct ducting, airflow, registers, and unit performance are brought together with consideration for ventilation requirements and building exhaust needs. The most important part of the mechanical plans is the list of "cfm" requirements next to each supply, return, intake, exhaust and ventilation opening. To conduct a Certified Air Balance, the building must first be totally sealed/enclosed. It is advisable that an HVAC specialized company like MBM do an air balance because they are able to not only adjust but repair and install parts as needed throughout the HVAC system in order to do an effective and long term air balance.

A total air balance requires an opposed blade damper (OBD) behind the face of each intake and exhaust opening in each room and of the building. Other balancing dampers are required at all branch locations of the duct system. Lastly, all filters in the system are changed and all dampers are fully open.

“We aren’t satisfied until you are satisfied.”

Readings are taken at every opening inside and outside. Slowly the dampers are closed in an effort to meet the cfm requirements. Adjusting one damper changes the cfm at all other openings. The air balance technician returns to every opening, making new adjustments and readings based on the changes from the previous one.

Registers, grills, exhaust fans, and fresh air must all "balance" to meet the system performance requirements. After the technician believes the system is all in tune, he locks down all of the dampers and other devices, so that the settings will not change.

Please be aware that the system can be thrown out of balance by such things as dirty filters, the home owner changing the register setting, remodeling, and reconfiguring registers and ducting.