What I'm Seeing Now


Because The J Sheet Says So

It was another new construction inspection, and another call from another supervisor.

"How did you figure out the air flow from the heat registers?"

On new construction I ALWAYS check the airflow from HVAC registers.  I do that because sometimes they systems are not balanced well, or connected properly or the ducts (glorified slinkies) are wrapped so tightly around rafters that they are crushed and don't blow air.  I should feel a strong air flow from each.  A good amount of air is between 400 and 600 cubic feet per minute.

"I use a meter, why?"  (You see it to the right)

"We think the airflow is fine because the J sheet says so."

This house has two systems.  The upper level system was found to provide 550CFM or better to one half of the house and 177CFM or less to the other half.  One register blew 63CFM.  That is a balance problem.  That system either lacks a damper or has one that is not adjusted properly.  In fact, one register in the master bedroom blew 589CFM and the other 149!

"What is the J sheet?"

"That's what the HVAC guy uses to pick out the duct sizes and how much air they blow out.  And some of what you wrote down is more air than the J sheet calls for.  And the County already approved it."

They always bring in the County to try to bolster their case.

"You mean the County and the J sheet want half the master bedroom to blow air at 1/4 the rate of the other half?"

I heard crickets on the line, hard to do when you are driving.

"I don't care what the County says.  Do you think I think they actually check the CFM rates?  And I don't care what the J sheet says.  It clearly doesn't say that half the upper level should blow air really well and the other half not.  That's a balance problem.  Don't you agree?"

He had no come back.  "You should have it checked out.  You would if it was your home."  End of conversation.

My recommendation:   Especially on new construction, but even if you are buying or selling an older home, walk around and feel the air blow from the registers.  It should be a strong blow.  If not, note it and have it checked out.  You will appreciate that in January and July.


Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560


Comment balloon 5 commentsJay Markanich • March 19 2010 07:19AM


Jay, its a new house, your not suggesting that something could be wrong?  I run into this on a regular basis myself.  Typically the HVAC contractor rolls his eyes at me and gives me that "How would you know" look.  I ask that all they do is check the CFM at the registers.  What is that, 1/2 hour maximum.  I've given my time to make sure my client is getting what they pay for, you would think the HVAC tech would gladly do the same.

Posted by Jack Gilleland (Home Inspection and Investor Services, Clayton) over 10 years ago

Jack - how often do they throw the "J sheet" at you?  I had never heard that one before.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 10 years ago

Hello Jay - Like Jack said, If it's new construction nothing could be wrong.  Great job.  Have a great weekend.

Posted by Andy Chaudoir, Your Home Inspection Connection in Central Texas (Professional Inspection Services - Georgetown, Texas) over 10 years ago

Jay- a lot of contractors just can't handle it when home inspectors know what their talking about.

Posted by Eric Middleton, Professional Property Inspector (Closer Look Property Inspections Inc.) over 10 years ago

Andy - I do a lot of new construction inspections and have more problems on them then I do on older homes!

Eric - this particular supervisor sat out in a truck smoking the whole time I was there.  The buyers had to leave so when I left and was carrying everything out he says, "Do you have a list for me?"  It isn't my purview to create a list for a builder of things for him to do.  I simply said, "No."  The buyers got their report later, but as to a list, I don't know!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 10 years ago

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