R19 Insulation: All Your Questions Answered

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R19 insulation is a popular choice for most modern homeowners, but is it correct for your needs?

Let’s look at how well this insulation works in different situations.

How Thick Is R19 Insulation?

R19 fiberglass insulation is usually around 6.25″ thick, but this can vary depending on the insulation material used.

The trick is that most wood framing studs are made from 2″ x 4″ lumber. Unless you have 2″ x 6″ studs, R19 insulation will be too thick for your walls.

Compressing insulation batts to fit in a narrower cavity will reduce its R-value. Don’t pay for higher-grade insulation only to lose the benefits by installing it incorrectly.

Rigid foam insulation rated at R19 is rare. Most foam panels only reach the R10 to R15 range. To achieve an R-19 rating, you’re going to layer several panels on top of each other. Even Polyisocyanurate (ISO), the foam insulation with the highest R-value, is only rated at R7.0 – R8.0 per inch of thickness.

Remember, there’s more to hitting that value of R19 than just material thickness.

Thicker is always better for insulation, yes.

However, factors like moisture, any facing materials, and the specific material you’re using can all affect how deep your insulation has to be to achieve R19.

Spray foam offers better insulation per cubic inch than fiberglass insulation, but it’s harder to install in some areas. Any gaps in coverage will significantly reduce its effectiveness. Many people supplement foam panels with foam spray or other options.

Fiberglass insulation requires more space, but it’s easy to install because you can shape it to fit almost any environment. It remains a popular choice anywhere you have enough space to not worry about the difference.

What Is R19 Insulation Used For?

R19 insulation is viable in several places around a house. Here are some common areas people consider putting it.


Unless you add additional layers, R19 insulation is not recommended for use in attics. And, at that point, we’re not talking about R19 insulation anymore.

Energystar.gov maintains recommended insulation values for different areas of the country. Even in the deep South, they recommend a minimum of R30 to R49 when adding insulation to an un-insulated attic. In colder climates, they recommend as high as R60.

Heat moves from warmer areas to cooler areas, and your home’s roof is often the coldest exposed area. Your attic should generally have the highest-rated insulation in your entire home.

Exterior Walls

Many modern home-builds come with 2″ x 6″ wall studs, which makes R19 insulation a popular choice.

Larger rooms require more insulation to be efficient and feel cozy. While R-19 may not be the best choice in older homes, it’s acceptable anywhere in the country in newer buildings.

Another common option is opting for R-21 insulation for exterior walls. Especially in colder climate zones, having a slightly better rating will usually pay for itself over time.

At a certain point, higher R-values just aren’t worth the additional cost. That’s because R-values aren’t linear. For example, R16 insulation is only about 5% more efficient than R8 insulation.

Additionally, recent studies found that fixing air leaks, and ensuring that moisture has somewhere to go is equally important.

Excess insulation without adequate ventilation can trap moisture inside a house, leading mold, mildew, or even rot issues. This is especially common when insulating basement walls. Only a professional energy assessment can determine whether you need more insulation in any specific area.


When I bought my first house, I was surprised to find out that my ceilings were not insulated.

If you think about it, it makes sense, even if it’s counter-intuitive.

Allowing the heat to move through the walls and floors helps maintain a consistent temperature throughout the house. Adding insulation can make some rooms noticeably colder or warmer than others.

The big exception to this is the garage.

Adding insulation to your garage ceiling can help keep the outside air away from your living areas.

For example, my master bedroom is directly over my garage. If my garage ceiling wasn’t insulated, all that heat would rise to my bedroom and my AC bill would be much higher.

R19 insulation is suitable for floors/ceilings in most homes, unless it’s the highest ceiling in a house. As we discussed earlier, ceilings at the top of a house with no attic, need significantly more insulation.

How Good Is R19 Insulation?

R-19 is a good amount of insulation for exterior walls across the country. Depending where you live, there may be better options, however.

Most common types of insulation have similar pricing per square-foot. Also, all things being equal, insulation with a higher R-value will usually cost more.

Also, remember that the insulation cost will depend on the specific type of insulation you buy.

Open-cell spray foam is usually the cheapest option, followed by blown-in fiberglass insulation, batting, and finally closed-cell sprays.

Even small changes, like upgrading from R19 to R21, or buying spray-foam vs batt insulation can substantially increase the cost of a large project.

Here’s how some other types of insulation compare to R-19.

R-19 vs R-13

R13 insulation is a good option for interior walls and floors. It will still allow some heat to move throughout the house, but it will help manage moisture or add soundproofing to your garage.

Although you won’t find it used on exterior walls, R13 insulation gets the job done inside.

The primary value of R-13 is reducing noise. Insulation will help blunt sounds, without totally blocking them.

Sometimes, you may want to intentionally make one room warmer or cooler than others, like a wine closet, or humidor. R-13 won’t completely stop the temperature from slowly balancing out, but it will help reduce the stress on your HVAC system.

R-19 insulation isn’t suitable for floors. However, it’s occasionally a better option in crawlspaces, especially in warmer parts of the country. It has significantly better insulating properties, but it’s arguably too much for most areas inside a house.

R13 insulation is noticeably cheaper than R-19. However, the savings usually aren’t worth efficiency loss for anywhere you usually want to use R-19.

R-19 vs R-21

Most homeowners will be choosing between R-21 and R19 insulation. To be honest, they’re almost always a good option in the same places.

Like R-19, R21 insulation is an acceptable choice when you have 2″ x 6″ wall studs. You can also use R-21 insulation in many crawlspaces, although that may be overkill.

R21 insulation usually has higher density than R19 insulation.

That sometimes results in a slightly thinner insulation, however you may sacrifice moisture handling. It’s a good option when you want to minimize the thickness of walls or literally can’t install thicker insulation. 

The primary difference between these two options is their cost.

R21 insulation has slightly better performance, but it’s more expensive. Remember that R-values aren’t on a linear scale. R19 insulation is more affordable, but only slightly less efficient.

R-21 shows its most value in relatively small buildings. There, the cost savings will be more apparent and show up sooner. It’s considerably more expensive to install over larger areas, where recoup the extra cost will take much longer.

Finally, while both options are viable everywhere, people in the coldest areas often prefer the extra insulation of R-21.

R-19 vs R-30

R-30 insulation is significantly more efficient than R19 insulation. Because of this, they’re often used in different areas.

R-30 insulation is the minimum rating for insulation in the three warmest zones of the United States. This includes most of the southeast, parts of California and Arizona.

On the opposite end of the spectrum, R30 insulation is also used in the four coldest areas of the country. You’ll find it used on crawlspaces and some internal floors.

In short, while R-30 is not a good choice for internal or external walls, it is a good option in most other places, depending on where you live.

That means it’s not a direct competitor with R19 insulation. Usually, anywhere you use one, you likely won’t use the other.

Outside of common areas, R-30 insulation may be appropriate for home variations, such as cathedral ceilings.

In rare cases, people may use R-30 to insulate an interior room, such as a warm office built into a colder garage. In these cases, thicker insulation makes it easier and more cost-effective to regulate the room’s temperature from the inside.

However, R-30 is noticeably more expensive than R-19, so many people try to minimize how much they need.

R-19 vs R-38

R-38 has the most significant difference from R-19, although it doesn’t see as much use as R-30. R-38, and even R49 insulation, is most suitable in the attics of homes in the five warmest regions of the country.

Unlike R-30, R38 insulation isn’t used in crawlspaces or other interior areas.

Remember that insulation’s thickness directly correlates to it’s efficiency. Homeowners insulating interior rooms usually don’t want to add the extra space necessary for getting walls insulated.

R38 insulation is the most expensive option, noticeably more so than R-19. Most parts of a house don’t need this much insulation.

Wrapping It Up

We’ve covered a lot about R19 insulation in this article. 

We’ve established that R19 insulation is typically about 6.25″ thick and is mostly used for exterior walls of houses with 2 “x 6” studs. Given its size, it may not be the right fit if you have narrower wall studs.

We’ve also covered why insulation’s effectiveness isn’t just about thickness but also considers factors like moisture, facing materials, and the specific insulation type. 

Finally, we compared R-19 insulation to other types, such as R-13, R-21, R-30, and R-38. The right insulation rating greatly depends on your specific situation, especially the climate in your area.

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Tim Wells

Tim Wells, the founder of Garage Transformed, has been featured in dozens of home renovation publications, including BobVila.com, Home Stratosphere, House Digest, Livingetc, and SFGate. Since 2018, he has helped over two million people transform their everyday garages into something they can be proud of. He lives in Central Florida with his wife and bulldog.

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