Do I Have to Replace my Ductwork When I Get a New Air Conditioner?

HVAC system ductwork

Ductwork problems don’t always require replacements. Your licensed HVAC contractor can perform tests to help determine the condition of your home’s system.

If your current HVAC system is getting old or isn’t working anymore, you’re likely getting estimates for a new system from local companies like Fox Family Heating and Air.  It’s wise to get a few quotes from different companies around town.  Just be careful.  My industry can be a little scandalous when it comes to salespeople telling you what needs to be done for your new system to work correctly.  For example, you may be told to replace your ductwork.

During a new AC installation call, I’ll often ask how the air distribution is around their house.  I’m asking if there are any hot or cold spots in the house.  Are there any bedrooms, offices, or living areas that they would like to get more air.  I would say about 80% of the people I ask say they’re just fine with the airflow they have.  All the rooms seem to be balanced, just fine.

Some people will say they have a problem room and would like it to get better comfort.  In an effort to rack up the price of your new HVAC system, salespeople may be focused on their own commission checks.  They will recommend you spend the extra $5000 to 10,000 to change your ductwork to solve the problem.  Is that really necessary?  I say no, not every time.  Here’s why.

HVAC Ductwork Repair

Ducts can be repaired individually.  You don’t have to replace every duct in your house to get better air to one or two rooms.  Those rooms can have more airflow delivered to those rooms by increasing the size of the duct leading to the room.  Another way to get more air to a room is to relocate the duct on the supply plenum to a spot that is more advantageous for getting air there.  Typically the end of the plenum.

You can fine-tune this process by cutting in manual dampers that can be adjusted to decrease the amount of air going to one side of the house so that it can be diverted elsewhere in your home.  I still recommend a professional do this.  Messing around with the ducts is similar to shutting down registers in your home in order to get more air to another side of the house.  This airflow disruption can cause high static pressure.  This can affect the more expensive mechanical parts of your air conditioning system.  The aerodynamics of the delivery system is essential to the longevity of the system.  That’s all I’m saying, so unless you know how to check static pressure in the ductwork, repairs like this should probably be left to the pros.

HVAC Ductwork Inspection

Your supply air ducts connect to your forced air unit.  The forced air unit is either in the closet, garage, attic, or in the package unit on the roof.  The air from that unit is sent into a big box called a supply plenum.  Attached to that supply plenum are several ducts that lead to each room of your house.  Here’s how to tell if those ducts are in good shape or not:

  • The ducts are strapped properly or lying on the floor of the attic.
  • Those ducts are straight, not bent or kinked, restricting airflow.
  • The duct’s vapor lining on the outside of the duct is not torn or melted.
  • Good to decent insulation, which maintains the temperature of the air as it heads towards the room that duct leads to.

There’s not a lot more you can ask from your ducts.  If they’re adequately strapped, meaning each duct is straight or has long sweeping bends (no kinks) that lead to where they need to go, and they have metal or vinyl straps that secure them in place, that’s a good sign.  Another thing that you’d like to see for your ductwork is that the vapor lining, which is yellow, pink, grey, black, or silver, is in good shape.

HVAC Ductwork Standards

Ductwork has an R-value to insulate your ducts to a set standard.  30 to 50 years ago, those standards were not as high as they are today.  So, ductwork has evolved in performance through the following stages:

  • The yellow and pink is actually insulation. They may or may not have a clear wrapping around them. This wrapping is the vapor lining.  If you have this setup, the ductwork may be original to the house, as it’s not too common to install them this way anymore.  You can expect this ductwork to be 30 to 50 years old.  It has an R-Value of two (R-2).  Not the best in the world, but I’ve seen people keep it because it works just fine, and I support them on that decision.
  • Grey ductwork typically has an R-Value of four (R-4). Once again, not the freshest ductwork we see out in the field, but if the ducts still meet those guidelines from above, people have chosen to keep that ductwork a little longer.
  • Black and silver ducts can have an R-Value of either R-6 or R-8. R-6 has been around for the last 25 years or so.  R-8 is the newest standard and has the thickest layer of insulation surrounding the inner lining.

HVAC Ductless Lifespan

I tell people your ductwork’s life averages about 30 years.  Some people replace them every time they get a new system, but most of the people I sell equipment to, don’t.  That’s because it’s impractical to do so.  Yes, the higher R-value of the ductwork, the better performance you’ll have.  The ductwork will hold the hot or cold air it’s delivering inside it better.  That translates to cooler or warmer air to your rooms, depending on which season it is.  Your decision is whether you want to spend the extra money to change your ductwork out every time you change your HVAC system.  Hopefully, I have armed with some useful knowledge going into your next project.  Good luck!

Recommended Posts