When you go insulation shopping, the first decision you come across is: which R-value should you choose? To put it simply, the R-value is the measure of how well an insulation material insulates your property. 

The higher the value, the more effective the material is. But it’s important to keep in mind that higher is not always better. 

As the R-value increases, so does the cost and installation complexity. Why put yourself through the trouble of using R25 insulation when R13 does the job? That’s why you should know which R-value will satisfy your needs. 

In this guide, we’ll do a comparison between R19 and R21 insulation. These two are commonly used in the attics, walls, ceilings, and floors of residential properties. 

What Is R19 Insulation?

R19 insulation is one of the highest-rated insulation products available. It has an R-value of 19, providing excellent thermal protection and energy efficiency. 

Some features of R19 insulation include: 

  • Easy Installation: There are two main ways to install R19 insulation materials. You can either use friction-fit (a technique that uses friction to hold the material in place) or staple the fiberglass batts in place. 
  • Easy Customization: All you need is a utility knife to fabricate and trim R19 insulation. It’s pretty easy to install this insulation around the nooks and crannies, especially around windows and uneven spaces. 
  • Noise Control: Most homeowners use R19 insulation for soundproofing purposes. It helps reduce noise and improves overall acoustic comfort in your home. 
  • Non-Corrosive: R19 insulation is non-corrosive to copper, steel, and aluminum. 

Where Is It Used? 

Like most other thick insulation materials, R19 is also used in walls and ceilings of residential properties. That includes attics, basements, and crawl spaces. 

If we talk about climate-based selection of insulation materials, R19 is better for northern homes. Plus, you should use R19 insulation if you have 2×6 wall studs. 

R19 Insulation Depth

The thickness of R19 insulation will differ across manufacturers. You can usually expect the thickness to be about 6.25 to 6.75 inches. The width of each roll will also vary depending on the manufacturer. For most, it’s 15 inches. 

What Is R21 Insulation?

R21 insulation has a higher insulation capability than R19. It is also more expensive but worth the investment in colder areas. 

R21 insulation shares many features with its R19 counterpart, such as acoustic benefits, easy installation, and non-corrosive properties. Here are some additional features: 

  • Lightweight: R21 insulation is lightweight enough to be used in walls and ceilings between rooms to muffle sound. 
  • Recycled Glass Construction: If you want to opt for a more eco-friendly insulation material, R21 is often made from recycled glass. 

Where Is It Used?

Although R21 insulation can be used in the same spaces as R19, it’s more commonly used in crawl spaces

The crawl space in your home is prone to extreme temperatures during the winter and summer. R21 insulation helps keep your crawl space insulated from the outside temperature to help regulate the indoor climate. 

In our research, we found that many manufacturers are making R21 insulation with plant-based binders. Since the material is free of formaldehyde, it’s ideal for allergy-prone individuals. 

Most manufacturers also make their R21 insulation without dyes and harsh acrylics. So, it’s an eco-friendly option for those looking to reduce their carbon footprint. 

R21 Insulation Depth 

Again, the depth will depend on the manufacturer’s specifications. We saw sizes ranging from 16″ x 96″ to 24″ x 96″. When you buy R21 insulation, check the square foot size per bag. 

Suppose you want to add R21 insulation in your crawlspace. The recommended depth is 6″ thick. We recommend measuring the area first and then purchasing enough rolls of insulation to cover it adequately. 

Which One Should You Choose, R19 or R21?

If you take an overall glance, both options are top-notch. But you should still consider the following when making a decision. 

Local Building Codes 

Some states and municipalities specify the level of insulation you should use. For example, R19 is a necessity in many building codes. 

You should check your local codes and use the insulation material accordingly. 

Climate Zone 

The farther up north you live, the colder the climate gets. As a result, you need an insulation material with better efficiency, which is R21. 

R19 also works, but if you really want to take your energy savings and insulation up a notch, go for R21. 

Existing Insulation 

If you’ve moved to a new space or are deciding to upgrade your home’s current insulation, check the R-value of the existing material. In most cases, adding another layer of R19 on top suffices. 

You don’t have to go all the way to R21 since it’s expensive and time-consuming. However, if the existing insulation is worn down and you’re planning to replace it altogether, you can decide between R19 and R21. 

Is R21 Insulation Better Than R19?

The question is quite like ”Is bigger better?”. Or ”Is more expensive better?” 

Not always. 

Yes, it’s true that R21 insulation has better capabilities. The acoustic and thermal insulation performance of this material is far superior to R19. 

But at the same time, it’s also more expensive and requires more insulation material for installation. 

So, it might not always be better for your situation. If you can make do with the cheaper option, there’s no reason for you not to go for it. 

Also, if the climate in your area is not too extreme, stick to R19 and save yourself a ton of hassle and money. 

When Should You Upgrade From R19 to R21?

Nowadays, the threat of climate change is looming over our heads like a dark cloud. Due to this, many homeowners are deciding to upgrade their insulation for hotter summers and colder winters. 

If you have similar plans for your home, you should upgrade the insulation to R21. 

Secondly, if you feel that R19 is not providing the efficiency you need, it may be time for an upgrade. For example, if the tenant (or your little ones) living on the top floor is too loud, and R19 seems to be helpless against the sound, you may want to install R21 insulation. 

Sometimes, you may have to opt for cheaper insulation because your budget, at that time, doesn’t allow the more expensive version. Now, let’s say it’s two years down the line, and you have the budget to upgrade. It’s worth it. 

Here’s what we’d suggest, though. Don’t simply upgrade for the sake of it. You don’t need to upgrade all your insulation material. Instead, just identify the areas where the existing insulation isn’t doing its job properly and upgrade those. 


Justin's been in construction for over 20 years in both new build and renovation. With experience in both commercial and residential construction, he specializes in healthier and more energy-efficient homes.

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