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Recommended Attic Insulation R-Value for Boise, ID

If you’re thinking of ways to save money this summer, chances are you’re considering insulating your attic. After all, attic insulation offers a lot of potential for energy savings—not just during the warm season but all year round!

You’ve decided you need to re-insulate. That’s the first step. Your next question is most likely, “How much attic insulation do I need?” To determine this, we need to look at the R-value.

What Is Insulation R-Value?

R-value is an efficiency rating for insulation. It refers to a particular insulation’s ability to resist heat flow. R-values vary based on:

  • Material
  • Density
  • Thickness

The higher the value, the more insulating ability the product has. To achieve a higher attic insulation R-value, another layer of insulation needs to be added.

How Is Insulation R-Value Calculated?

Let’s start at a base point: Solid wood has an R-value of 1. An R-value is also calculated per inch of width. Therefore, a three-inch-thick board has an R-value of 3. Blown fiberglass installed in the attic has an R-value of 2.2 per inch, so 12 inches of it would give you an R-value of 26.4.

What Is the Recommended Attic Insulation R-Value for the Boise Area?

Different areas of your home have different R-value recommendations, and homes in different areas of the country have different recommendations based on the climate and cost-effectiveness of the insulation. What is the recommended attic insulation in Idaho?

Insulation R-value climate zone map of the U.S.


For homes in the Boise, Idaho area, the insulation R-value climate zone is 5. If you look at the chart above, you can see that the attic should achieve an R-value between R38 and R60, depending on the current insulation levels.

Looking for expert home insulation contractors in Boise? Contact us online or call 208-488-4962 to schedule attic insulation services!

How Much Attic Insulation Do I Need?

What do your current attic insulation levels look like? To start, poke your head up in your attic and briefly survey; this is one of the quickest and easiest ways to tell if you need more attic insulation. Can you see your floor joists (the wooden beams running across the floor)? If the insulation is level with or below the joists, you probably need to re-insulate the attic.

Even if your joists are not visible and you think you may have enough attic insulation, there could be hidden air leaks that are significantly reducing the insulation’s performance. Too many air leaks can render insulation essentially useless.

Besides manually checking, there are other ways to tell if you need to re-insulate the attic.

  • Are your energy bills higher than normal for the time of year (with no increase in usage)?
  • Is the second floor of your home unusually warm?
  • Has your AC been running more than normal?
  • Did ice dams form and/or did snow melt too quickly off your roof during the winter?

If you have noticed any of these signs, or you notice one or more of them this summer, you may need more attic insulation. If you’re unsure, that’s completely fine—it’s what the pros are for!

Attic Insulation Services in Boise, ID

This is a lot of information, but keep in mind that you won’t be on your own! Professionals can complete your insulation installation so it’s done correctly.

Need insulation services in the Boise area? The team at Big City Insulation of Idaho has you covered. Contact us today to learn more about us or to schedule a free estimate!

Services We Provide
Residential Insulation

Our insulation team adds energy efficiency, comfort and value to new and existing homes.

Commercial Insulation

Big City Insulation of Idaho is a leading installer of commercial fiberglass, rigid board and rockwool insulation.

Insulation Removal

Big City Insulation of Idaho provides home insulation removal services.

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