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R13 vs. R15 Insulation: What’s The Difference?

A home needs to be properly insulated so the occupants stay warm in the winter and cool in the summer. And when it comes to insulation, two kinds are often purchased by homeowners: R13 and R15.

These insulations are similar yet different, and in some situations, R13 is better while R15 is better at other times. In this article, we assess R13 vs. R15 to see which insulation is better overall. If you install the insulation that’s best for your home, it’ll be more efficient and comfortable. There’s a lot to cover, so let’s begin!

What Is Insulation R-Value?


R-value is a metric that’s used to determine how well a material can resist heat. The higher the R-value, the more heat-resistant the material is. When it comes to insulation, heat resistance is largely determined by what the insulation is made of.

Insulation can be made of spray foam, fiberglass batting, rock wool, and cellulose. Some materials have an R-value of 60, and at present, this is the highest R-value a material can possess.

Generally speaking, spray foams have the highest R-value, but this is also the most expensive insulation option. Plus you’ll need a professional to install this. Most homes are insulated with either fiberglass rolls or batting, as these options are affordable and easy to install.

In the end, the kind of insulation you need largely depends on the room where it’s being installed. For example, an attic will need insulation  that has a higher R-value because it could get very hot or very cold in this space without such strong and efficient insulation

Now that we’ve covered R-value, let’s look closely at the factors that in part determine what kind of insulation is necessary for a particular situation.

What Factors Are Relevant When Determining Which Insulation Is Best?

A variety of factors are relevant when you’re trying to determine which insulation is best for your project. Some of the important ones are discussed below.

1. The Room Being Insulated

When you’re insulating first-story floors, walls, and ceilings, the insulation’s R-value doesn’t have to be all that high. It’s really only in the attic and basement where you’ll need insulation that’s stronger.

The kind of heating and cooling system a room utilizes will also play a role in determining what kind of insulation is necessary. And if a room is frequently exposed to direct sunlight, this should also be taken into account before installing insulation.

2. The Climate

The climate your home is in is also relevant when you’re determining which insulation is best. For example, if you live in Florida, you won’t need insulation that’s stronger than R15, whereas homes in the Northeast are usually outfitted with insulation that’s between R25 and R30.

Note: R-value is higher in colder climates largely because keeping heat indoors is of vital importance in such climates.

3. Your Budget


The stronger the insulation, the more expensive it is. The reason why stronger insulation costs more are that the materials used to make this insulation are more expensive. Plus, the process used to make stronger insulation is more complicated and requires more time.

Now that we’ve covered the R-value and the peripheral factors that in part determine what kind of insulation is necessary, let’s compare R13 and R15 insulation to see which is superior.

R13 vs. R15: Which Is Better?

Before we compare R13 and R15 insulation, it should be pointed out here that the main difference between these two insulations is that one is more heat-resistant than the other. That being said, there are other important qualities that may lead you to choose one kind of insulation over the other.

In fact, you may even find yourself in a situation where you’re choosing R13 over R15, even though you need the added heat resistance—but more on that later.

Below, we compare R13 and R15, focusing specifically on composition, applicability, noise-canceling ability, energy efficiency, moisture resistance, pest resistance, and maintenance.

1. Face

Faced insulation includes a kraft-paper vapor barrier so the material is more moisture-resistant. Unfaced insulation, on the other hand, does not have this protective barrier, yet it’s still used frequently, often with preexisting insulation.

If you’re in a climate that gets humid, or there’s frequent rainfall, it’s wise to get faced insulation, especially in the areas that are most exposed to moisture, i.e. the attic and basement. The thing about moisture is it can lead to mold growth, and if mold grows on your insulation, a total insulation replacement may be necessary.

Both R13 and R15 insulation can be faced or unfaced. However, a material with a higher R-rating is more likely to be faced. That being said, if you want a high R-rating but you don’t want the extra protection (and the added expense), there’s no reason why you can’t go with an unfaced R15.


2. Applicability

Both R13 and R15 insulation shine in terms of applicability, as both insulations can be used in walls, floors, and ceilings. Moreover, both insulations work well with 2 x 4 walls, as there’s usually about 3.5 inches of space behind these walls—plenty of space for both insulations.

Note: If you have 2 x 6 walls, you’ll need R19 insulation or higher. Insulation with a higher R-rating is required because this material is thicker and able to fill the wider space.

3. Noise-Canceling

Insulation isn’t just important because it regulates a home’s temperature; it also helps with noise reduction. If you live next to a busy road, having thick insulation could make the outside world less noisy.

There’s actually insulation that’s specifically designed for noise reduction, and this insulation is not only soundproof but heat-resistant as well.

At present, spray foam insulation is the best noise-canceling insulation, and you can find R13 spray foam insulation as well as R15 spray foam insulation. Homeowners often soundproof their garage, basement, and office.

If you want to go for max noise cancellation, insulate your ceilings with R19 and use R13 for the floors and walls.

4. Energy-Efficiency

Energy efficiency is probably the most important factor that distinguishes R13 from R15 insulation. In short, R15 is more energy efficient than R13, which means you should go with the former insulation over the latter if you’re concerned about wasting energy (and money by extension).

Of course, the difference between the two values is only two digits, so R15 isn’t all that more heat-resisting. And in some situations, it may even be better to use R13, like when there’s a tight space that needs to be plugged up.

In the end, if ensuring top-quality energy efficiency is your main goal when installing insulation, go with R15 over R13.

5. Moisture-Resistant

As was mentioned earlier, considering moisture control when selecting insulation is important as well. And how well insulation repels moisture is determined by a range of factors, including the material used and climate.

You also need to ensure proper ventilation, as doing so will help prevent excess moisture from accumulating. R-value and moisture are not related, but it’s true that insulation with a higher R-value tends to be more moisture-resistant. Again, this is because higher R-value insulation tends to be faced.

You should also know that if the insulation gets damp, such will decrease its R-value. In some cases, you can have something as strong as R-19 become as weak as R13 because it stayed damp too long.


6. Pest-Resistance

The type of insulation you choose also plays a role in determining how well your home resists pests. Your insulation should be treated with specific pesticides so critters and insects don’t make the insulation their home.

You can reach out to any local pest control company when you need insulation infestation prevention services. The kind of critters you’ll need to keep out are spiders, moths, mice, and ants. Termites  can also spread in the insulation before they start eating the wood.

R13 and R15 are pretty much the same when it comes to preventing pest infestations. However, it can be argued that R13 is more pest-resistant since it’s thinner.

7. Lifespan

Both R13 and R15 are long-lasting. In other words, you could get decades out of these insulations before they start to wear down and you need replacement insulation. So when it comes to lifespan, it’s pretty much a tie.

That being said, one could argue that R15 lasts longer because it takes more time for heat to erode this material.

Final Verdict

The bottom line is this: R15 has an edge over R13, but it’s a slight edge that specifically comes from its ability to resist a little bit more heat. In the end, you could use insulation for walls, floors, and ceilings and expect similar results. After all, it’s not like comparing R13 to R30.

So if you really want to choose the insulation that’s superior on paper, go with R15 insulation.

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