R6 vs. R8 Ducts: Major Differences and Which One to Pick

Ducts are essential for heating, cooling, and ventilating your home, and one small detail can affect how efficiently they perform—their R-values. These identifiers indicate how resistant a duct is to thermal changes and are determined by factors like density, thickness, and what it’s made of. R6 and R8 ducts are among the most common options for interior venting. But aside from the two-number difference, you may not know what sets them apart when it comes time to look for an air duct replacement. 

This guide breaks compares R6 versus R8 ducts, including which to pick to keep your energy bills low. 

R6 vs. R8 Ducts: Key Differences

Air duct R-values can range anywhere from R1.5 to R11 and apply to all types of ductwork (including rigid and flex ducts). However, R6 and R8 are two of the most common options. The biggest difference between them is their thickness, which directly correlates to how efficiently they heat and cool a home. Though they’re made from the same materials, air ducts with higher R-values are thicker because they contain more insulation than thinner options with low R-values: There are 2 inches of insulation in R8 ducts and only 1.5 inches in R6 ducts. 

That doesn’t automatically mean that R8 ducts are always the right choice. Yes, they limit heat loss and cut energy consumption by 3% annually—a boon for those in cold climates—but they don’t necessarily offer anything special to those living in places that are warm year-round. Plus, R6 ducts are more affordable since they use less material, are smaller, and are more flexible for easier DIY installation. 

What Is an R6 Duct?

R6 ducts are those that contain 1.5 inches of insulation. While they provide better heat regulation than ducts with lower R-values (like R4 or R2) they don’t have the same energy-saving benefits as R8 ducts.

Best for: 

• Anyone living in a year-round warm climate. 

• Those looking for affordable ductwork, or who want to try installing it themselves. 

Pros of R6 Ducts

At just $100 per 25 feet of ductwork on average, R6 ducts are considerably less expensive than R8 ducts. What’s more, they’re also easier to cut and fit into small spaces thanks to the fact that they’re thinner than their competitor—making DIY installation that much more doable with an option like this. 

Cons of R6 Ducts

Although less insulation makes R6 ducts easier to install, it also means they aren’t as energy efficient. Although the difference isn’t that great, this option won’t provide the same cost-saving, home-heating benefits as R8 ductwork. 

What Is an R8 Duct?

R8 ducts contain 2 inches of insulation, which makes them better at warming your home and maintaining that heat. However, you’ll have to budget a little more for these added benefits.

Best for: 

• Cold climate dwellers

• Anyone who wants to reduce energy costs 

Pros of R8 Ducts

Though an extra half-inch of insulation might not seem like a lot, that alone can reduce annual energy consumption by up to 3%. Plus, those in warm and cold climates will benefit from the increased insulation, as it does a good job of maintaining hot and cold air alike. 

Cons of R8 Ducts

While worth the purchase if you can swing it, R8 ducts do come with a couple of drawbacks: Namely, they’re more expensive than R6 ducts—at $150 per 25 feet of ductwork on average—and harder to install on your own because of the extra thickness. If you do pick this option, plan to find out who does ductwork in your area and hire a local duct installer. 

R6 vs. R8 Ducts

Now that you’ve brushed up on the basics, here’s how these two duct types compare.

Price: R6 Ducts

There’s no denying that R6 ducts cost less up front and are easier to install on your own, meaning you could save on the costs of hiring a pro. 

Ease of Installation: R6 Ducts

The smaller duct size of R6 ducts makes them easier to cut and fit into tight spots, both of which are key for having an easy installation.

Eco-Friendliness: R8 Ducts

Less energy consumed doesn’t just keep costs down—it also lowers your carbon footprint. 

Length of Life: Tie

Because they’re both made from the same materials in varying amounts, their durability is similar. You can expect a 10 to 15-year life span from ducts of any R-value.   

Maintenance: R6 Ducts

Being easier to fit into small spaces means that R6 ducts are also easier to repair and maintain than the bulkier alternative. 

ROI: R8 Ducts

R8 ducts' energy-saving potential could significantly reduce your energy bill, which means a better return on investment despite the higher initial cost.