Why it’s important for your ductwork to match the size of your system

Year after year, manufactures produce “higher efficiency equipment”, but will these new products truly deliver the savings you are looking for?  The short answer is “yes”, but it’s not only about the equipment.   In my experience, when customers are looking to purchase an HVAC system, they’re fixated on just the equipment and what SEER rating it delivers.  However, what they don’t realize is that when an HVAC contractor does a Manual J heat load on the house to determine the size of the system for the house, the ductwork must match the size of the system.  So if you need a 3-Ton unit for your house, you will need a duct system that delivers 1200 CFM, which is the amount of air a 3-Ton unit delivers.   If not, you could be wasting money on that new, expensive high efficiency unit you’re thinking of buying.  An inadequate duct system can cost you up to 40 % of the system’s efficiency.

I like to use the straw analogy. Take a straw from McDonalds.  If you ever grab a straw from McDonalds and blow through it, you’ll notice that there is no resistance. You probably didn’t have to work very hard to feel air come out the other end.  Now take a coffee straw and blow through it.  I’ll bet you’re huffing and puffing to notice a little bit of air coming out the other end.  It’s the same concept with your air conditioner and duct system. You’re the air conditioner and the straw is the duct system.  It has to work harder to produce the amount of air it is moving… which, in return, means higher electric bills, possible repair problems, and performance issues because it’s unable to deliver the air it needs to cool your house.

The key is to make sure you ask your contractor about the ductwork, how big your duct system is, and if the air conditioning system he is proposing will match your duct system.  Remember, when most people change out their heating and cooling systems, they have a low efficiency unit and are looking to upgrade to a higher efficiency unit.  Don’t spend thousands of dollars for a high efficiency unit if your ductwork isn’t correct.  If it’s not in the budget to do both, then go with a lower efficiency unit and get the ductwork fixed.  You’ll be much happier with your system from an energy and comfort standpoint.

Amount Of Air Put Out By Each System Size:

  • 1.5 Ton system delivers 600 CFMs of air
  • 2.0 Ton system delivers 800 CFMs of air
  • 2.5 Ton system delivers 1000 CFMs of air
  • 3.0 Ton system delivers 1200 CFMs of air
  • 3.5 Ton system delivers 1400 CFMs of air
  • 4.0 Ton system delivers 1600 CFMs of air
  • 5.0 Ton system delivers 2000 CFMs of air

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