Chris' Corner: HVAC Ducting Issues

HVAC Ducting Issues

Uneven heating or cooling a very common problem in homes. There can be several causes of this issue.  In this post, Jay Markanich discusses how he located the root cause of the problem and illustrated how important good home inspections are.

If you are looking for a property in New Tecumseth, call me, Chris Smith @ 1.866.936.3500 for information and assistance to help you find the property just right for you.

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"Our air conditioning doesn't blow very hard." How often have I heard this!

"Well, it blows hard in two rooms. In the rest it's very weak. We'd like you to try to figure out why."

This time it was over the phone when someone scheduled a new-construction warranty inspection.

And they were right. On the middle level, the main living space, two rooms blew air at nearly 700 cubic feet per minute. That would be pretty high. The rest had various air flows, but all weak, in the 100-200cfm range. The basement was similarly weak.  Ideally 400-600cfm is a good air flow.

So we went downstairs. Off the HVAC unit was a main service duct which blew the conditioned air toward the middle of the basement family room. Through the entirety of the ceiling space was a 6' wide bulkhead. That obviously housed the main HVAC trunk, off of which were attached all of the 90 degree runs servicing each of the HVAC registers in the basement and main levels.

   So I had a look with the thermal camera!

This is the ceiling under where the main service duct runs inside the cavity between the furnace room and the central trunk.  The left image is where it exits the furnace room and the right where it connects to the bulkhead.

The lavender, blue and purple indicate cooler temperatures.

The coolest temp shown is 55.5F.  So inside that cavity it must be a bit cooler than that! 

What's going on?  Either there is a tear in the duct, one of those round, flexible, glorified slinky ducts, or it has come loose where it connects to the central trunk.

Obviously a lot of air is being pumped into the cavity and all of it is NOT blowing into that central trunk!  Some air is obviously pushed around the house, but not a lot.

And why were those two rooms serviced with such a powerful air flow?

Looking at the unit, there were two individual, smaller ducts run directly to those rooms.  Because of their place in the house, it was more efficient to do it that way than to go back to them from the central trunk.

MYSTERY SOLVED!  Now the builder has definitive proof that there is a problem which can only be addressed by removing drywall and reconnecting or repairing the tear in the duct.

I did run into an interesting thing though!

When viewing the air conditioning unit in the basement, and where the main trunk exits the appliance, I saw this!

Mosby!  Waving as usual.

I havent' seen him in a while.  I wonder, was he fooling with that duct?

Was he the gremlin that disconnected that duct from the trunk?

We won't know probably.  But it's indisputable that he was there.  He's a pip!

My recommendation:  one or two year warranty inspections are essential!  And beware.  Some builders do their one year at 11 months, and two year at 22 months!  YOU MUST PAY ATTENTION TO WHAT YOUR CONTRACT SAYS!  If you miss your window, you miss your opportunity.  And warranty inspections usually reveal lots of things that the builder should do.




Jay Markanich Real Estate Inspections, LLC

Based in Bristow, serving all of Northern Virginia

Chris Smith CSSBB
          Sales Representative

Interested in Buying or Selling Real Estate?

  ph: 1.866.936.3500

Chay Realty Inc.,

Comment balloon 0 commentsChris Smith • September 06 2011 10:31AM