· by Michael Blair, Nashville's Insulation
Efficiency work varies enormously in return, and the ranking is fairly consistent. Spending in order rather than by enthusiasm gets the most from a budget.
The order that pays
Air sealing first, then attic insulation, then duct sealing and insulation, then crawl space work. All four are relatively inexpensive and address the largest losses in a typical Nashville house.
Windows and wall insulation come far later, despite being what people usually ask about first.
Why walls rarely pay in an existing house
Injecting insulation into existing walls is disruptive and expensive relative to the loss it addresses, because walls are a smaller share of the loss than the attic and the ducts.
It makes sense when walls are already open for other work, which is a different calculation.
- Air seal the ceiling plane first
- Attic insulation to current depth
- Seal and insulate ducts in unconditioned space
- Crawl space encapsulation in this climate
- Windows and wall injection last
Getting an assessment
A blower door test and a duct pressure test quantify where the losses actually are, rather than guessing. It costs relatively little and it stops you spending on the wrong thing.
Some utility programs offer assessments and incentives, which is worth checking before commissioning work privately.
The comfort argument
Payback calculations undersell it. A sealed and insulated house is more comfortable, quieter and less humid, and those are the things people actually notice day to day.
In a Middle Tennessee summer, the difference in an upstairs bedroom is often more persuasive than the bill.