Air Conditioning Design – Tips For Getting it Right the First Time

Getting air conditioning right the first time is important for your home’s comfort, both now and  well into the future.  Proper design, installation and sealing of ductwork increases efficiency, which reduces your monthly energy bills and ensures that your A/C system can give you the best possible comfort.

Designing an air conditioning system correctly means, first and foremost, sizing the system correctly.  A/C equipment must be sized to the home based on certain criteria and calculations:

  • climate
  • size and shape of the home
  • insulation
  • location and type of windows
  • types of appliances in the home

In order to get your air conditioning right the first time, your HVAC contractor should use calculations called Manual J and Manual D to size your system.  These calculations were developed by the Air Conditioning Contractors of America (ACCA), and they are the standard accepted in the U.S. today.  Manual J is used to size your system based on the above criteria.  Manual D refers specifically to duct design.

Duct systems must be sized to the heating and cooling equipment.  If ducting is undersized or oversized, or has been pinched or bent during installation, its ability to allow air to flow could be compromised leading to low air flow rates and high air velocities. Why does this matter?  Low air flow rates cause your A/C equipment to operate inefficiently. High air velocities make your system noisy.

Many older A/C systems were oversized at the time of installation to compensate for leaky windows and poor insulation that allow too much air exchange between the indoors and the outside.  Since many factors affect what requirement your home has for heating or cooling (known as its “load”), your contractor should perform a load calculation.

Make sure to get a report from your contractor when he or she has completed this calculation, and ask for a warranty when the work is done.  Getting your air conditioning right the first time means partnering with a good contractor who knows the proper way to size your A/C system.