What is insulation R-values?

Insulation R-value is a measure of the thermal resistance of insulation material. It measures how well the insulation resists the flow of heat through it. The R-value of insulation is a function of the type of insulation material used, its thickness, and its density.

The higher the R-value of the insulation, the better it is at reducing heat loss or gain through walls, floors, and ceilings. For example, an insulation material with an R-value of 30 will provide more thermal resistance than one with an R-value of 20.

Insulation R-values are used by building professionals to determine the appropriate amount of insulation to install in a particular location. Building codes typically require a minimum R-value for new construction, and homeowners may choose to add additional insulation to improve the energy efficiency of their homes.

The R value is, in essence, the measurement of an insulation sheet’s ability to resist heat flow.

Basically, R valves range from 1.5 to 7, and the higher the number is, the more effective the insulation sheet is at increasing thermal efficiency, and thereby, insulating your home. Within the R value of insulation, there are three kinds of R values that are commonly used to more specifically measure heat flow resistance variables:

• The Down R Value: The down R value (also known as the summer R value) is a measurement of an insulation’s ability to resist heat flow from coming into the house. The reason it is sometimes called the summer R value is because, in summer, you want to keep the heat out.
• The Up R Value: The up R value (also known as the winter R value) is a measurement of an insulation’s ability resist heat flow from escaping the house. The reason it is sometimes referred to as the winter R value is because, in winter, you want to keep the heat in.
• The Total R Value: The total R value is, in most cases, what is referred to when you hear the blanket term ‘R Value’. It is a combination of the up and down R values.

What Insulation Has The Best R Value?

The easiest way to approach this question is to begin with the concept that there is no ‘best’ R value. Any insulation that carries a higher R value is going to be more effective than that with a lower R value, but the truth is that a higher R value is not always required for every home.

Different regions are broken up into ‘climate zones’, with each zone requiring a different minimum R value, based on its climate. For example, homes in climates that are extremely hot and humid only require R values of 3 or 4, while homes in freezing, alpine climates require a minimum R value of 6.

What R-Value Insulation Do You Need?

While the R value of 7 is more effective than the R value of 3, If you live in a home that is in a very hot climate, it would potentially be wasteful, unnecessarily expensive, and counterproductive to install insulation with an R value rating of 7. The best insulation is the one that suits your home and environment’s unique conditions the most effectively.

Types of Insulation and Their R Values

There are three very common and well trusted types of insulation:

1. Bulk Insulation: Easily the most popular and commonly used insulation around today, bulk insulation is designed with countless tiny air bubbles throughout the material, which it traps the hot air in. Rather than being made of just one material, bulk insulation comes in a range of different materials, including polyester, fiberglass, wool, recycled paper, and cellulose fiber. Bulk insulation too comes in a wide range of R values.
2. Foil Insulation: Foil insulation is a clever form of insulation that has a reflective surface on one side. It acts by deflecting radiant heat from the outside, back into the environment—which is why it is the best insulation for hot and sun-prone environments. The advantages of foil include that it is cost effective and easy to install. Foil insulation comes in a wide range of R values.
3. Spray Insulation: A newer addition in insulation technology, spray insulation is made of foam and is surprisingly effective. As the name suggests, It is applied by being sprayed in the ceiling, floor, or in walls, and it expands into thick insulation. It is moisture resistant, but is also more flammable than traditional insulation, which is why we recommend it is installed by professionals only. A great advantage of spray insulation is that it has the ability to reach higher R values than any other insulation material.

How To Measure The R Value of Insulation

When manufacturers produce insulation, they do so with specific R values. So when you are buying insulation, consult your supplier to get more detailed information on what exact R value each insulation carries.

Your home doesn’t necessarily need the highest R-value insulation. The R-value your insulation needs depends on your local climate.  

The map above shows each region of the U.S. and the Department of Energy’s corresponding climate zone. Once you find your home’s zone on this map, you can use the below insulation R-value chart to determine the minimum R-value your insulation should have. 

Selecting The Right Insulation

Find your zone on the map and then use the above insulation R-value chart to determine the level of insulation you need to properly insulate your attic, walls, floors and crawlspaces. These R-values are a sum, meaning this should be the total R-value once you add up the entire depth of insulation. For example, if you have a type of insulation that has an R-value of R-5 per inch of thickness, you will need a depth of 6-inches of this insulation installed in your attic to reach R-30 if you live in Zones 2 or 3.  

The R-value of insulation can be affected by factors such as air leakage, moisture, and compression. Proper installation and maintenance are important to ensure that insulation maintains its R-value over time.

It’s important to choose insulation materials that are appropriate for the intended use and meet safety and environmental standards. Some materials may have higher R-values but may also pose health or safety risks, so it’s important to consider all factors when selecting insulation.