What is a good R-value for exterior walls? | airflow academy (2023)

You want to renovate your home and you make lists of everything to include in the renovation process. Renovating your home's old insulation—especially on your exterior walls—is high on the list. But anytime you search online for more information about the "right" insulation for your exterior walls, you'll come across the term "R-value" and discussions about a good R-value for exterior walls. The questions you have are, first, what exactly is an "R-value" and also what is a good R-value for exterior walls.

Typical R-value recommendations for exterior walls are R-13 to R-21. The required R-value for the walls depends on the climate zone you live in. Colder regions require a higher R value, while temperate regions require exterior walls with lower R values.

What is a good R-value for exterior walls? | airflow academy (1)

In this article, I will not only provide a table of recommended R-values ​​for exterior walls, but also briefly explain general aspects of R-values ​​and how insulation works.


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General R-value considerations

When discussing and researching R-value for exterior walls, it's always a good idea to also consider other insulation aspects related to the outside of your home. While I will primarily address exterior wall insulation, I will also cover aspects such as the attic, crawl space, and flooring.

The R value refers to heat resistance

As mentioned above, the R-value is an internationally recognized measure of the heat resistance of an insulation material. Thus, the higher the R-value of the insulating material, the more resistance the material can offer to heat loss.

The R-value can be different in the house

It's important to realize that the R-value of all insulation materials in your home is not necessarily the same. For example, the R-value required for the insulation of your attic is likely different than the insulation required for the exterior walls of your home. And insulation with a different R-value for the floor may be required. Generally speaking, theTypical recommendations for exterior walls are R-13 to R-21, while R-30 to R-49 are recommended for attics.

The region in which the house is located affects the required R-value

The area you live in and the average temperatures in the area also affect the R-value of the insulation you should use. For example, a colder climate requires higher R values ​​than a more temperate climate.

Other aspects that affect the R-value

Other aspects that affect the required R-value of your insulation are the size of your home, the type of HVAC system used in the home, and the material used in the walls, floors, and roof.

Why is isolation necessary?

Now that you know that the R-value gives an indication of the resistance that heat encounters when entering or leaving your home, let's look at why it's so important to have heat in or out of your home to keep.

Simply put, insulation is necessary to keep heat in your home (in the winter) and outside (in the summer) so your HVAC and/or furnace air conditioning system will keep your home at a comfortable temperature during the heat of summer and the chill of winter . The better the insulation, i. H. the higher the R-value of the insulation material, the more heat stays inside or outside the house.

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So insulation with the right R-value will save you money on your energy bill. Your air conditioner and furnace don't have to work as hard and continuously, consuming a lot of unnecessary energy if your home is well insulated.

How insulation works and what to insulate

ways of heat transfer

Heat can be transferred by conduction (transmitted through substances - for example electricity), convection (movement of hot air or liquid rising and cold air or liquid falling), or radiation (heat traveling in a straight line in the form of waves or waves). become ). particles).

purpose of isolation

The purpose of insulating your home is to reduce conductive and convective heat flow. However, if, for example, your exterior walls are well insulated but your attic is not adequately insulated, in the summer heat will travel from the warmest parts of the house to the coldest parts of your house, such as the attic, until the temperature is the same everywhere.

In the summer the opposite will happen. The poorly insulated attic allows heat to enter your home, causing your cooling system to work harder to remove heat from your home.

What other exterior parts of the house need maintenance?

When insulating your exterior walls, you should also pay attention to the following external aspects:

  • Outward opening windows and doors.
  • The roof.
  • Floors - especially above an uninsulated basement.
  • Barrier-free foundations between soil and concrete.
  • track spaces.

What is a good R-value for exterior walls?

The R-value for your exterior walls varies depending on where you live. If you live in the northern US you need the highest recommended R-value and in warmer regions you need insulation with the lowest recommended R-values.

Key US climate regions and recommended R values ​​for exterior walls

There are 7 major climate regions or zones in the United States and each has its own weather patterns and temperatures. The seven regions are

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  • 7. Northwest Coast,
  • 6. plateau,
  • 5. Midwest,
  • 4. Mid-Atlantic,
  • 3. Southeast,
  • 2nd South and 1st Southwest, including Guam, Hawaii, Puerto Rico and the Virgin Islands.
  • The 8th separate zone includes neighborhoods in Alaska.

Table of R values

Use the table below to find recommended R-values ​​for exterior walls;

Zone2 x 4 outer walls2 x 6 outer walls
7N / DR-19 and R-21
6N / DR-19 and R-21
5R-13 and R-15R-19 and R-21
4R-13 and R-15R-19 and R-21
3R-13 and R-15N / D
2R-13 and R-15N / D
1R-13 and R-15N / D

In summary: On average, insulation R-values ​​for exterior walls range from R-13 to R-21.

What insulation material is best for exterior walls to deliver the right R-value?

Depending on the summer and winter temperatures in your area, a good R-value for exterior walls is between R-13 and R-21. (See table above.) Any of the following exterior wall insulation materials can be used to achieve this.

  • Fiberglass.
  • foam panels.
  • Cellulosic insulation.
  • Stop isolation.
  • Closed cell or open cell spray foam.

Fiberglass mat is one of the most commonly used materials, but when using it remember that a 2x4 wall can only accommodate up to R-15 insulation and a 2x6 wall can only accommodate R-21 insulation. If you live in an area with extreme temperatures and want more than R-21, you'll need to use a different type of material.

How to use insulation material to get required R-value

It should always be remembered that the R-value is directly related to the thickness of the insulation material. For example, a fiberglass mat typically has an R-value of R-3.7 per inch of thickness. If you use two stacks side by side, the R value is 2 x 3.7 = 7.4. So if you needed an R value between 14 and 15 you would stack 4 on top of each other.

The relationship between R-value and insulation is linear. So the higher the R-value of the insulation used, the less you have to spend on heating in the winter and cooling in the summer. But you have to find a trade-off between R-value, wall thickness and how much you can afford to spend on insulation.

R-value rule in the US

Remember, according to the FTC's R-value rule, you need to know what the R-values ​​of the insulation in your home are before you sell your home. The Federal Trade Commission (FTC) regulates this R-value rule. The full name is "Trade Regulation Relating to the Labeling and Advertising of Home Insulation Rule".

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Insulation manufacturers and installers, as well as home sellers, are required to provide consumers with R-value information based on standard test results. The main purpose of the rule is to ensure that a prospective home buyer is informed that the home is adequately insulated.

frequently asked questions

Q1: How much R value does it matter?

A1:Doubling the R-value halves the heat loss. So adding R-1 to existing R-1 insulation makes a big difference, but adding R-1 to existing R-30 insulation only reduces heat loss by about 3%.

Q2: Is the R value always per inch?

A2:Yes, insulation values ​​are always measured in R-values ​​per inch of insulation thickness.

Q3: How do you increase the R-value of a wall?

A3:By adding more ceiling insulation between wall studs or installing foam board insulation, you can increase the R-value of a wall - interior and exterior walls.

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When your exterior walls and other outdoor parts of your home are insulated with the recommended R-values ​​discussed in this article, you save energy because your air conditioner and furnace don't have to work continuously to keep the temperature in your home comfortable. . Keep in mind that a good R-value for exterior walls is between R-19 and R-21 in the northern parts of the US and between R-13 and R-15 in warmer parts of the country.


What is the maximum R-value for a 2x4 wall? ›

Fiberglass and rock wool batts—2x4 walls can hold R-13 or R-15 batts; 2x6 walls can have R-19 or R-21 products.

What R-value and facing of insulation should be used in 2x4 exterior walls? ›

Insulation for 2x4 Walls

In most wall applications, you will use R-13 or R-15 kraft-faced fiberglass insulation rolls for these two-by-four stud walls. While rated differently, these two types of insulation are close enough in thickness that they can both fit into modern two-by-four wall systems.

What type of insulation is best for exterior walls? ›

Best Insulation for Open Exterior Walls
  • Fiberglass Insulation. Fiberglass insulation is one of the options that is going to require tearing down your drywall. ...
  • Foam Board Insulation. ...
  • Spray Foam Insulation. ...
  • Blown-In Cellulose Insulation. ...
  • Injection Foam Insulation.
May 12, 2021

What R-value insulation goes in a 2x6 wall? ›

The installed insulation R-value for 2x6 fiberglass batt ranges between R-19 and R-21. When blown or sprayed cellulose insulation is used, the R-value is typically R-20 for 2x6 walls.

Is it worth insulating exterior walls? ›

Insulation on exterior walls puts a blanket-like barrier between your living area and extreme outdoor temperatures. Insulating your walls can prevent this by limiting air movement, enabling you to save up to 40 percent in heating and cooling bills.

What insulation to use in 2x4 exterior walls? ›

In most applications, you will use R-13 or R-15 kraft-faced fiberglass insulation rolls for two-by-four stud walls. While rated differently, these two types of insulation are close enough in thickness that they can both fit into two-by-four wall systems.


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