Under-applied insulation – or no insulation – in your exterior walls could have a big impact on your energy bills. To assess the insulation situation in your home’s outer walls, try these methods:
Method one: Choose an electrical outlet that’s located along an exterior wall and turn off the circuit breaker for that outlet (you can plug in a lamp or small appliance before and after you shut the circuit to make sure there’s no power feeding the outlet). Remove the wall plate and use a knitting needle or clothes hanger with a hook on the end to probe the wall cavity for insulation.
Method two: Find an exterior wall in a closet or under the kitchen sink (a conditioned garage space can work, too) and turn off the circuit breaker that supplies power to that wall. Using a hole or drywall saw, cut a 1-2″ hole in the exterior wall; this will give you a clear view of the insulation, including its thickness (which will help you determine its R-value).
Just like your attic, an unconditioned crawlspace or basement can have a significant impact on your energy bill. Here’s some guidance on basement and crawlspace insulation:
Check insulation under floors of conditioned living space – Follow the same R-value guidance as described in the Attic section above.
Insulate the sub space perimeter – According to energy.gov, If your crawlspace or basement is enclosed and contains heating or cooling appliances, air ducts or plumbing, it’s a better bet to insulate the sub-space perimeter rather than the living space floor. The insulation at the top of the foundation wall and first floor perimeter should have an R-value of 19 or greater. If the basement is conditioned, the foundation walls should also be insulated to at least R-19. Your water heater, hot water pipes, and furnace ducts should all be insulated.
Do your research!
Once you have a better idea of your home’s insulation situation, do a little more research about options for improving it so you can spend less on your bills next year. Here are some resources from the U.S. Department of Energy to get you started: