Connecting new air conditioning equipment to an old duct system doesn’t always spell disaster, but it often does. Here in the San Marcos, Buda, Kyle and New Braunfels area of Central Texas, most air conditioning and heating duct systems are located in attics. Attic ducting presents some very specific problems when it comes to air ducts.

First: Attic ducts are exposed to temperature extremes. Attic ducting will normally have an R6 or R8 insulating factor compared with a home’s R19 or even R38 ceiling insulation. Many older homes will have attic duct insulation as low as R4. I know talking about R numbers is a little confusing, so let’s put this into perspective.

The air used to heat cool your home, must first pass thru the hottest and coldest place in the house (the attic) inside a duct system that has less insulation than any other part of your home. Is that crazy or what?

Second: If any air leaks out of ducts located in an attic, the conditioned air is being sent outside the living area of the home. Assuming that all the air being brought into the air conditioner is being taken from inside the living area (and it should be) the leaking attic ducts are causing the living area to be in a slight vacuum. This vacuum (or negative pressure) caused hot, humid, unfiltered air to be sucked into the home thru cracks, crevices, doors, and windows. This just adds to the cost of heating and cooling a home and may mean the house cannot be cooled on hot summer days. Cooling problems aren’t always the fault of the air conditioning equipment … sometimes it’s the air ducts.

Still, we haven’t considered connecting that new air conditioning system to an old duct system. HVAC contractors are notorious for installing duct systems that are too small. Why? Because doing things right requires design time and time is money and probably more materials and labor cost and an extra one hundred dollars might mean a contractor doesn’t get the job and it’s all about doing the cheapest job at the lowest price …right?.

The right thing to do is verify that the old duct system will work with the new air conditioning system. How? AirOne Heating and Air Conditioning uses Total Performance Diagnostics to verify air flow performance. Correcting air duct problems to insure proper operation of a new air conditioning system doesn’t always have to be expensive and time consuming. It doesn’t automatically mean a duct system needs replaced. But not checking, evaluating, and verifying how the new air conditioning system and the old duct system are going to work together shouldn’t be an option.

When replacing an air conditioning system, don’t ignore the air ducting. A bigger air conditioning system is not the right solution for bad air ducts. High efficiency air conditioning systems will never produce the promised savings when connected to an old duct system that can’t move the right amount of air.

AirOne Heating and Air Conditioning uses Total Performance Diagnostic to routinely identify air flow problems on every service call. Contact an AirOne Heating and Air Conditioning professional for more information or a duct system evaluation.