One very important aspect of a pre-drywall inspection, is to check for proper distribution of HVAC systems. Modern HVAC distribution tubing includes a lot of flexible stuff, a slinky really, made up of a slinky-like spring, wrapped in plastic, surrounded by insulation and then another final layer of plastic.
Another thing to look for is how the flexible ducts have been treated. Slinkies, if you recall, were easy to manipulate. They could be smashed and come back springing!
At times these flexible ducts are wrapped so tightly around joists or roof rafters that they are literally crushed.
The more they are crushed the less they are able to blow air.
You want them to blow air!
Sometimes rooms are hot or cold. Part of the reason might just be that they are not getting enough air introduced to control the temperature environment.
The duct to the left services a rather large master bathroom. It is a 6" duct and should blow 400 to 600 cubic feet per minute of air (cfm).
Hard to see in the photo, but easy when up close, is that it was bent so much that the opening just above the hole is only about 2" wide.
That won't blow much air.
It also becomes a problem long term in that closing off this opening causes back pressure inside the duct and can literally pop the duct off of the main trunk to which it is attached. I see popped-off ducts all the time! Then the attic is conveniently heated and air conditioned! Excellent!
The pre-drywall inspection is the time to catch this! Once the drywall is up and the register is in place, it is much harder to see the size of the opening servicing a room's register.
My recommendation: the next time you are walking through new construction, look around, and especially up, to see how the flexible HVAC ducts have been treated. Is the distribution even and logical? Are they wrapped too tightly? Or bent severely around a joist or rafter? Or maybe even torn? This is crucially important to the final operation of the system and the comfort of the home.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560