The HVAC system on a house is just that - a system! When installers are not completely thinking the sytem is much, much less efficient.
The exterior wall of a house is composed of an exterior "skin," (some form of siding) to shed water and wind, an exterior sub wall (plastic wrap and something basically structural), structural framing composed of wood or metal studs (2x4s, 2x6s), insulation, sometimes a vapor retardation indoors, and drywall. Basically that is it. There are variances, of course.
However, if the outside wall is composed of 2x4s, the space is narrow. There is not much room for insulation!
Plumbing and duct work inside that wall must be protected!
On this pre-drywall inspection, this is the only HVAC duct servicing the front room on the lower level.
This is the largest room on that level.
This is a small duct,only 4".
This duct is, necessarily, fitted into a small space.
This duct's register is teeny for such a large room.
Even given all that, the above doesn't represent my biggest beef.
THIS IS AN UNINSULATED DUCT ON AN EXTERIOR WALL!
See the space high and low to the left of this duct? That insulation is incorrectly jammed into there. Insulation wants to be as full as possible as its job is to trap air. Crush it and it loses its ability to trap air, and thereby providing LESS insulation!
Insulation's job is to provide a thermal barrier. Its ability to do that is labeled in terms of its RESISTANCE VALUE or R-value. The higher the number the better the insulation!
When you crush this insulation the R-value is reduced. IT SHOULD NEVER BE JAMMED INTO A SPACE!
This outside wall is to receive bat fiberglass insulation, the rolled stuff. It is labeled R-13. That gives an effective R-value of about 11.1.
ALL OVER THE HOUSE INSULATED DUCTWORK HAS BEEN INSTALLED. WHY NOT HERE?
This is the problem now:
- If the insulation is stuffed BEHIND this flexible duct, both the insulation and duct will be crushed behind the drywall. It's already a small duct! Crushing it will reduce its ability even more to blow air. And the insulation will have less R-value. The result is reduced efficiency.
- If the insulation is stuff AROUND this flexible duct, both the duct and that space of exterior wall it occupies are uninsulated! The result is reduced efficiency.
They have themselves between a rock and a hard place!
I can only wonder why they would do this? There are insulated ducts all over this house. Why not here!? Probably because an insulated duct is too fat for the space! Then why not use the ceiling?
My recommendation: You can see here that the insulators did not know how to handle this space! They are waiting for "direction." Drywalling over this space would have hidden a huge and long-term problem! Thinking must be done in advance. When you see something that might not be thought out completely, bring it up! Don't be shy!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560