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What Insulation R-Value Do I Need?August 25th, 2023 by
When it comes to improving the energy efficiency of your home, the focus is often on windows and HVAC systems. While these are effective ways to keep energy bills low, insulation is as much, if not more important. You should always have the right amount and type of appropriate R-value insulation for different areas in your home.
Insulation offers thermal resistance to heat transfers that make your home cold in the winter and hot in the summer. Choosing the right type of insulation and getting an appropriate R-value for your climate will limit energy leaks and keep your home more comfortable year-round.
From a basic understanding of the thermal resistance of insulation to how the listed R-value prevents heat loss, here is everything you need to know about what insulation R-value to choose for your home.
What Is R-Value in Insulation
The R-value, or thermal resistance value, is a measure of the thermal resistance of a material to the flow of heat. In simpler terms, it measures how well insulation keeps the heat on one side from transferring to the other side.
The higher the R-value, the higher the resistance. Insulation works year-round to keep the temperature inside your home even and comfortable. As a result, better insulation will keep your cooling costs down in the summer and your heating costs lower in the winter.
But this doesn’t mean you should upgrade to the highest R-value you can find. R49 or R60 insulation is necessary for extreme climates, but they can be an unnecessary expense if you live in a more temperate area.
Typical R-values range from R13 to R60, although some products may offer higher or lower values. The higher the R-value, the better the insulating power of that material.
R-values are based on the thickness and density of the material. Different types of insulation provide certain levels of thermal protection depending on the thickness of the material.
While the exact thermal resistant values vary depending on the brand and product, here are the average ranges per inch of thickness for the most common insulating materials:
- Cellulose insulation: 3.5
- Fiberglass insulation: 2.9 to 3.8
- Foam board insulation: 6.5 to 6.8
- Spray foam insulation: 3.8 to 7
Basically, this means that cellulose and fiberglass insulation needs to be roughly twice as thick to offer the same insulating power as foam board and spray foam materials.
However, the exact R-value can vary based on the inch of thickness. Manufacturers all use slightly different materials and production methods, so products may vary slightly.
What Insulation R-Value Do You Need?
Choosing the right R-value for insulation depends on several factors. This includes your climate, where the insulation is going, and even the style and construction of your home.
For example, if you live in a colder climate, you will likely need more insulation than someone who lives in a warmer climate. While you might need R49 insulation in Boston or Chicago, R30 is more appropriate for Nashville or Charlotte.
Also, different parts of the home require varying levels of heat flow resistance. You will traditionally need more insulation in your attic than in your floors or a garage.
The US Department of Energy recommends insulating your home to an R-value of at least R30 for walls and attics, and R15 for floors. However, this is just a recommendation.
You should always have an insulation installation company conduct an energy audit to ensure you are choosing the right insulation and R-values for your home.
Insulation With Radiant Barriers
Aside from the density and thickness, some types of insulation also include a radiant barrier. This is a reflective foil that acts as a mirror of sorts, blocking out heat and cold before it can even enter your home.
Radiant barriers are most common on fiberglass rolls or batts and rigid foam boards. However, separate reflective barriers are available and can be installed with most insulation.
Some brands market this material as reflective insulation. As an added benefit, the reflective material also acts as a moisture control barrier. This helps protect against moisture absorption.
Insulation R-Values By Zone
The appropriate thermal resistance value depends on your location in the country and where the insulation is being installed. Since heat rises, you will use higher-rated insulation in the ceiling than in walls, flooring, or basements and crawl spaces.
|Exterior Walls||Flooring||Basement or
|1||R30 to R49||R13 to R19||R13||R13|
|2||R30 to R49||R13 to R19||R13||R13 to R19|
|3||R30 to R60||R13 to R19||R25||R19 to R25|
|4||R38 to R60||R13 to R21||R25 to R30||R25 to R30|
|5||R38 to R60||R15 to R21||R25 to R30||R25 to R30|
|6||R49 to R60||R15 to R21||R25 to R30||R25 to R30|
|7||R49 to R60||R15 to R21||R25 to R30||R25 to R30|
It is important to remember that these are estimates. You should discuss your needs with a qualified insulation installer before deciding on the right R-value.
They will discuss your insulation options and recommend the appropriate thermal resistance values to fit your climate.
How Long Will Insulation Last?
On average, insulation lasts 35 to 80 years. However, the actual lifespan be much longer.
Most types of insulation offer peak protection for 25 to 50 years. Spray foam insulation typically lasts upwards of 80 to 100 years. While they may offer less protection over time, they will still offer some insulation for much longer.
Fiberglass insulation will easily last more than 100 years, and foam products will last more than 150 years. But again, they will offer less protection against heat loss than during their peak lifespan.
Just because the insulation lasts for decades, does not mean that it offers the right level of protection for your home. Insulation, especially foam and cellulose products, has become more efficient in recent years.
Also, energy recommendations and local building codes have changed dramatically since even the early 1990s. If your home is more than 25 years old and you have not upgraded your insulation, you are likely out of date.
Your options are to add more levels of insulation or replace the existing material entirely. The best way to decide which option is the most effective for your home is with an energy audit.
How Damage Impacts Insulation Performance
The estimates above assume that the insulation remains in good condition. Moisture and water damage will decrease the insulation effectiveness of cellulose and fiberglass materials. Cracks and impact damage will affect the efficiency of foam products.
Water is especially damaging to cellulose blown-in or loose-fill insulation. Water will damage the cellulose material, limiting the insulation’s effectiveness. It can also lead to mold issues.
The only option if water damages your cellulose insulation is to remove and replace it.
Adding Layers of Insulation
One way to improve the insulation of your home is to simply add more since the R-value of insulation has a cumulative effect.
This means you can add the R-values together when you add another layer of insulation. For example, adding a new layer of R13 fiberglass insulation over your existing R13 material adds up to R26 protection.
However, you should never press or squish insulation materials to fill in a space. Insulation is designed to take up space and prevent heat from transferring through the material based on its thickness and density.
Compressing the insulation reduces its ability to stop heat transfer. Pressing two 9-inch thick batts of R13 fiberglass insulation into the same space will not give your R26 protection. Instead, it may actually give you less than R13 protection.
Alternatively, you can choose to replace your existing insulation to address temperature differences throughout your home. However, the best solution really depends on your home and your insulation needs.
This starts with evaluating your home and your current insulation. It may even include a detailed energy audit using thermal imaging. Your insulation installation company will walk you through the steps before beginning.
Most insulation companies are happy to educate you about their products. This includes explaining the insulation types, the best R-values for your home and climate, and other factors related to your house.
Best Pick Reports is the fast, free, and reliable way for homeowners to find prequalified insulation companies across the country. All you need to do to find an insulation company near you is to enter your ZIP code.