What Does the R-Value of Insulation Mean?

The R-value of insulation is its ability to resist the transfer of heat through the insulation. Heat transfer is the loss of warm air from inside the home to the exterior. It also implies the transfer of heat during the warm summer months from outside into the home. So, insulation with high R-values resist heat transfer much better than insulation with low R-value.
Gable View of Ongoing House Attic insulation Project with Heat a

To give you a good comparison, the attic insulation in newly built homes have an average R-value rating of 44, while concrete blocks used around the foundation have an R-value of 1. This is why it is common to add spray foam insulation in between the openings found in concrete blocks.

The R-value is directly related to the thickness of the insulation and the air density. For example, regular fibreglass insulation must be twelve inches deep in order to achieve around an R-value of 38. On the other hand, loose cellulose insulation only needs to be about 10 inches deep to have the same R-value.

Now that you know what the R-value means, it is important to keep in mind different areas of your home have different minimum recommended R-values.

  • Crawlspaces: R-19
  • Exterior Sidewalls: R-18
  • Basement: R-19
  • Attic: R-44

Depending on when your home was built it may lack these minimum values. Adding insulation to exterior sidewalls, crawlspaces, and basements can be difficult and challenging. Yet, increasing the amount of insulation in your attic is fairly easy because you are essentially “topping off” the existing insulation.

“Topping off” your attic insulation and increasing the R-value to at least R-44 could potentially reduce your home’s heating costs this winter by as much as 20%. Plus, the additional insulation will help keep your home cooler in the summer and could save you as much as 10% off summertime cooling costs.

  • TIP: If you have an electric furnace or electric baseboard heating, it is recommended to increase attic insulation to a minimum of R-49. This is because electric types of home heating tend to be less energy efficient and can cost more, compared to natural gas heating.
  • Bonus TIP: For maximum savings on heating and energy bills we recommend topping off attic insulation to an R-value of R-60.

How to Calculate Your Current R-Value in Your Attic

The easiest way to get an idea of the current R-value rating for your existing attic insulation is to measure it with a tape measure. Carefully push the end of the tape measure down without disturbing the insulation as best as possible, until you hit the baseboard underneath.

  • TIP: You will want to wear gloves, a facemask, and protective goggles when measuring the depth of fibreglass insulation because fibreglass can irritate the skin, eyes, and respiratory system.

For both fiberglass and cellulose insulation, every inch of insulation is approximately equal to an R-value of 3.5. So if you have 10 inches of insulation in your attic, it roughly has an R-value of R-35, which is under the minimum recommended amount.

If you need assistance in determining the R-value of your attic insulation or want to have it topped off before it gets really cold, please feel free to contact Logik Roofing at 905.424.7469 today!


“We are proud to be part of the GreenON Rebate Program, where you can earn up to $1,500 in rebates just for topping off your attic insulation!”

Enbridge Rebate