The R-value of an insulation material indicates its thermal resistance. That’s what most people know about the unit. 

But what does a higher R-value equate to? Do you always need the highest R-value for optimal insulation performance? 

The R-value you need for your building will depend on several factors like climate, budget, material type, building codes, etc. In this article, we’ll discuss two R-values, R15 and R19, and compare the differences between them. 

What Is R15 Insulation?

R15 insulation refers to any insulation material with an R-value of 15. The material may be mineral wool, cellulose, fiberglass, or others. R15 insulation is usually sufficient for the floors and walls in most homes and buildings.

With R15 insulation, you can ensure a thinner sheathing without compromising on insulation performance. For instance, an R15 insulation with a thickness of 3.5 inches will be 36% more thermally resistant than an R11 fiberglass insulation. 

Where Is It Used?

Whether you can use an insulation material in a certain region or area will depend on its climate zone. The climate zone encompasses the climate conditions, such as temperature, moisture levels, and wind chill, of the location. 

The US Department of Energy divides the US into eight climate zones. Of these, R15 insulation can be used in the first two zones. In Zone 1 and Zone 2, you can use R15 insulation to insulate floors. 

If you have uninsulated wood-frame walls, you can also use R15 insulation in combination with continuous insulation of R10 to insulate them. 

The use of R15 insulation is not limited to Climate Zones 1 and 2. It can also be used in any home from Zone 1 to 7, particularly in 2×4 walls. Similarly, R15 insulation is also suitable for crawl spaces in Zone 2. You may also use this insulation material in the foundation, ducts, and exterior walls of your home. 

R15 Insulation Depth 

R15 insulation is usually 3.5 inches thick. For reference, if you purchase the 15 in. x 93 in Kraft faced fiberglass insulation batts from Home Depot, per bag will cover 67.81 sq ft of area. The product length is about 7.75 ft, while the width is 15 inches. 

If you’re unsure about how much insulation you need for your home, use an insulation calculator. You can also consult a professional contractor for accurate insulation calculations based on the area of your house. 

What Is R19 Insulation?

R19 insulation is a type of insulation material used in homes with very cold climates. It’s thicker than the R15 variety and provides better thermal protection. 

It can be made from fiberglass, recycled paper, or cotton-like materials called ‘denim’ batts. Its common thickness is 6 inches or more, which makes it suitable for floors, walls, and crawl spaces. 

Where Is It Used?

Again, we refer back to the climate zone guide by the US Department of Energy. According to it, you can use R19 insulation in any zone except Zone 8. 

For instance, R19 insulation is suitable for uninsulated flooring in Zones 3 and 4. Similarly, the insulation can be used in uninsulated wood-frame walls. 

If you want to use R19 insulation in the attic in Zone 1, you have to make sure the attic already has 3 to 4 inches of existing insulation. R19 insulation is also used in projects that use 2 x 6-inch lumber since the thicker insulation fits better into that type of framing. 

R19 insulation can also be found in many commercial projects, such as commercial buildings or warehouses. It is also commonly used for soundproofing between walls and floors to reduce noise pollution. 

R19 Insulation Depth 

The usual thickness of R19 insulation is 6.75. Some materials, such as fiberglass or recycled paper, may be slightly thicker. If you want to get the most thickness, go for fiberglass loose-fill insulation, whereas batt insulation will suffice if you only need a thickness of 5.2 inches. 

Which One Should You Choose: R15 or R19?

We already explained earlier that the choice of insulation depends on your climate and what part of your house you are insulating. Consider these factors when you have to make a decision. 

Area to be Insulated 

For colder climates, like Zone 5 and lower, R19 insulation is a better option since it provides better thermal protection. It also fits well in 2 x 6-inch lumber. 

On the other hand, R15 insulation should be used when you need less thickness in the insulation, like in uninsulated floors or walls. It also works best for areas that don’t require as much thermal protection, such as Zones 1 and 2. 


Cost-wise, R19 insulation is more expensive than R15 since it offers better thermal protection. As a rule of thumb, insulation with a higher R-value is almost always pricier than the one with a lower R-value. 

If you have budget constraints, R15 insulation is a better option since it will provide adequate thermal protection and cost less. 


In some applications, such as attics, you may need more insulation thickness. In such cases, R19 is the better option since it provides more depth than R15 insulation and gives greater protection from heat loss or gain. 

Other areas of the home, like walls or floors, may not require as much protection. In such cases, R15 insulation is sufficient. 

Is R19 Insulation Better Than R15?

You’d think so, wouldn’t you? But higher thermal resistance does not always mean better. Sometimes, you don’t even need that much protection. So, why spend all that extra money? 

Which of the two is better will depend on your individual needs. Some homes may need R19 insulations, while others will see excellent results with just R15. Consider your climate needs and budget before you make a decision. 

When Should You Upgrade From R15 to R19?

Sometimes, upgrading from a lower R-value to a higher one is not only required but also inevitable. For example, if your building codes require a higher R-value, you have to comply. 

The building codes in your area determine the minimum insulation requirements for new construction and major renovations. In the case of existing buildings, you may need to upgrade your insulation if it is not enough to meet the energy conservation requirements. 

Plus, you may want to upgrade your insulation if you’re planning to sell your home and get a higher resale value. Insulation is an attractive feature for potential buyers and can add value to your home. 

However, you should always consult a professional before you undertake any insulation upgrade. Don’t just focus on the ”more and more R-value” mantra. It’s important to analyze your climate conditions and insulation needs beforehand. 


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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