Exterior Wall Insulation: How to Tell if You Need More Insulation

Exterior wall insulation

Spring is finally here in Michigan! It was an unusually long and cold winter this year with very few breaks in the subzero temperatures. I’m sure some of you out there are shaking your heads, wondering how in the world your energy costs could have been so large.

We cover a lot about insulation in your attic but what about walls? Do you know what kind of insulation is in your exterior walls? Do you know how to tell?

This is important because 30% of your home’s energy costs – heating and cooling – is in the air leakage in and out of your home’s walls.

Tips on Finding Out How Much Exterior Wall Insulation Your Home Has

There are a few tips to help you get started if you don’t know the answers to these questions.

What age is your home?

This is the easiest way to tell because we know when building codes started to require insulation. Before those codes were written, natural gas – or coal in the case of a very old house – was so cheap they didn’t bother insulating the walls. Some homes prior to 1930 were not built with a wall cavity that can accept new insulation.

Here’s the quick rundown:

  • Before 1960, homes were not insulated. If your house is that old and a previous homeowner didn’t have it done, you probably don’t have it.
  • Between the years 1960-1970 some homes were insulated. In 1965, the code changed, so new homes had to be insulated with 2’’ thick R-8 if your wall cavity is 3.5’’ thick. So it’s probably not adequate and most contractors can retro-fill the cavity completely. This can really reduce air leakage in your home and enable you to see a big difference in your energy bills next winter.
  • If your home was built after 1971, you are probably fine. At that time, 3.5’’ thick R-11 fiberglass batt was used almost all the time on new homes and if this is the case, you probably won’t have any space to add more.
  • If your home was built after 1990, you are in even more luck! The R-value of your wall insulation is R-13.

Other Ways to Check Wall Insulation

There are two other ways to check for wall insulation or energy performance.

An Energy Audit

The less invasive one is to pay for an energy audit from your gas or electric company. They are not very expensive and they can help you pinpoint with more accuracy where your home is losing most of its heat. This is because they have those infrared guns which can detect air leakage in and out of your house.

The Wall Test

Another less invasive method, but far less accurate, is to feel your exterior walls in cold weather to see how cold they are. If they are just above freezing, you probably have little to no insulation. You can also try removing a switch plate to see if there is a gap between the electrical box and the drywall into which you can shine a light.

Following those methods, you will need to drill a hole in an inconspicuous place, like a closet or a pantry on an outer wall. Be very careful not to hit any electrical lines or pipes and don’t press hard. You don’t want to drill a hole in the insulation, just see if it’s there.

How to Fix It

This isn’t really a DIY project, as it can be a fire hazard. You need an experienced contractor who knows the codes as insulating around electrical fixtures and recessed lights can get tricky.

If you want to replace the siding on your house, it’s the perfect time to beef up your insulation. Otherwise, siding can be temporarily removed or an unfinished attic can be accessed to blow insulation in your walls from above.


Unfortunately, our predecessors didn’t always plan for gas and coal prices to skyrocket the way they have now. When energy was cheap to get, building codes reflected this. However, it’s definitely more cost-effective in the long run to insulate your outer walls and your attic now before you lose any more than you have to next winter in energy bills.

If you live in the Southeast Michigan area, please give us a call. We are here whenever you need us!

Call today!


You may also like to read:


Leave a Reply