Updated: Nov 21, 2022
Most of the time, when we think of the word envelope, we think of the outer covering that our mail comes in. Or, to irritate our kids or coworker, we might push the envelope.
However, your home’s envelope consists of its outer walls, windows, doors and other openings. A well-sealed envelope, coupled with the right amount of insulation, can reduce your energy use — and, in turn, your utility bills.
According to EnergyStar.gov, a whopping 9 out of 10 homes in the U.S. are under-insulated. Homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by air sealing their homes and adding insulation in attics, floors, over crawl spaces and basements.
To determine if your home’s envelope is in good shape, conduct a home audit to pinpoint the leaks that allow energy to escape your home — air-conditioned air in the summer and heated air in the winter.
A qualified energy auditor will include an insulation check as part of a whole-house energy assessment and will identify areas of your home that need air sealing or insulation repairs. As your electric cooperative, we offer members energy audits to assist you in determining where your home may need additional “envelope TLC.” And as a bonus, don’t forget to check our rebate program when you determine what steps you need to take to tighten up your home’s envelope.
DIY home energy audit
If you prefer to complete your own energy audit rather than calling on a professional, you’ll need to know:
The type of insulation in your home.
The R-value (rate of thermal resistance) of your insulation. Typically, the higher the R-value, the more effective it is at insulating. Depending on where you live, you do not necessarily need the highest value; it depends on your local climate.
The thickness or depth (inches) of the insulation you have.
In a newer home, the builder can help identify the type of insulation used and where it is located. In an older home, you will need to perform the inspection yourself.
Energy.gov offers detailed advice on where to insulate, insulation in new homes, adding insulation to existing homes, types of insulation and materials, moisture control and air sealing. Find details here. One note: You may read about radiant barriers as a way to save energy. Our experts caution that radiant barriers do not provide any real energy savings in Iowa, as our climate is a “heating dominant” region.
Safe Electricity offers a quick overview on how to complete a DIY energy assessment by checking:
In the attic
A general rule of thumb when inspecting the attic insulation is that if the insulation is level with or below the attic floor joists, you probably need to add more insulation.
If you cannot see any of the floor joists because the insulation is well above them, you probably have enough, and adding more insulation may not be cost-effective.
Insulation should be evenly distributed with no low spots; be sure to check throughout the attic to determine if there are any thin spots.
Make sure the insulation in your attic has the appropriate R-value for where you live. Check the value printed on your existing insulation. If you cannot find the value, measure the depth of the insulation in inches. Multiply the depth by the following insulation type: 3.2 for fiberglass batting, for the loose fibers category, multiply by 2.5 for loose fiberglass, 2.8 for rock wool and 3.7 for cellulose. Then check EnergyStar.gov’s recommended R-values. If your calculated value is less than the recommended levels for your region, then you should consider adding more insulation to your attic.
Behind the walls
Turn off the power to the outlet before beginning this check. Then use a voltmeter or voltage tester to confirm that there is no power at the socket before beginning work.
Remove the outlet cover and shine a flashlight into the crack around the outlet box. You should be able to see if there is insulation in the wall and possibly how thick it is.
Pull out a small amount of insulation if needed to help determine the type of insulation.
Check outlets on all floors, as well as old and new parts of your home. Just because you find insulation in one wall does not mean that it is uniform throughout your home.
How to conduct a DIY air leak audit
This simplified set of instructions is also from Safe Electricity.
Before you repair or install more insulation, you need to identify and repair any potential air leaks in your home’s envelope. Potential problem areas include doors, windows, sill plates (the bottom piece of wall structure where wall studs are attached), top plates (supportive beams in the ceiling), crawl spaces, outdoor faucets, dryer vents, stove vent fans, roof eaves and overhangs, plumbing vent stacks, recessed lighting, attic hatches and air duct registers.
One way to have your home checked is by a qualified energy auditor. Or, if you want to address your own home, there are a couple of ways to do this:
By yourself Perform a visual inspection on your own in daylight. All potential problem areas should be free from gaps and cracks. While lights are on in the home, also observe from the attic, crawlspace or basement. Anywhere you can see light from the interior of the house shining through gaps and cracks is another air leak location in need of repair.
With a partner To conduct a more thorough inspection, work with a partner at night to shine a flashlight over all potential gaps while one of you observes the house from the outside. Anywhere you can see light shine through is an air leak that needs to be sealed properly.