What Insulation To Use For 2X6 And 2X4 Walls

Disclosure: We may get commissions for purchases made through links in this post.

Using the proper insulation is critical to maximizing home comfort and energy savings. So, you might be wondering what specific insulation to use for 2x6 and 2x4 walls. Well, in this post we combine industry professional knowledge and up-to-date research to answer your question.

For 2x4 and 2x6 walls, you can use a wide variety of insulation types. Which type works best depends on your stage of construction, budget, available tools, DIY skills, and preference. Generally, consider these three insulation types for both 2x6 and 2x4 walls:

  • Fiberglass batts
  • Blown loose-fill insulation
  • Spray foam insulation

Keep reading the rest of this post for details on each of the above insulation types and considerations for how to install them in 2x6 and 2x4 walls. To conclude, we'll answer a few related questions to the topic of this post. Without further ado, let's get into it!

Wooden framing of a house with spray foam insulation, What Insulation To Use For 2X6 And 2X4 Walls

What Insulation To Use For 2X6 And 2X4 Walls

The insulation types recommended here are generally considered the industry standard for all home wall types. However, for any insulation to be effective, the proper size needs to be installed according to the manufacturer's recommendations and local code requirements.

In the following subsections, we'll consider these three recommended types of insulation and the proper size for both 2x6 and 2x4 walls. After reading this guide, you should have all the information you need to make an informed wall insulation decision.

Fiberglass Batts

Fiberglass batts are the most popular and most affordable type of wall insulation. Further, this insulation is relatively easy to install even without prior experience.

A worker placing mineral insulation between for the framing

To determine the exact type and size of fiberglass batts that are appropriate for your walls, you need to understand the dimensions of your framing bays. The depth dimension is already indicated by the 2x4 or 2x6 designation. However, the width of the bays can vary.

When measuring the width of your wall framing bays, the goal is to understand the typical bay width. That is to say, most bays will be a standard size despite periodic bays that are smaller or rarely larger. Thus, measure several bays with a tape measure until you are sure of the standard width.

Once you understand the standard width and your depth, you can shop for fiberglass batts that fit those dimensions. The product will be labeled with both the appropriate depth and width.

Click here for faced fiberglass batts for 2x4 walls from Amazon.

For walls, you can choose either faced or unfaced batts. Faced batts generally provide better air barrier quality and a slightly higher R-value, but they are also more expensive. Consult local standards to decide if faced or unfaced insulation is right for you.

Also, you have the opportunity to choose between regular batts and high-density batts. High-density batts are more expensive but also provide a higher R-value. If you can afford them and live in a colder climate, high-density batts are usually well worth the additional price.

How to Install Fiberglass Batts

With batts that are designed to fit your standard bay, the goal is to install the batts so that they fill all the space without being compressed at all. This means that you will have to cut the batts down both vertically for skinny bays and horizontally where bays end.

Click here for eye and breathing protection from Amazon.

In fact, it is best to cut pieces of batts for all small and off-shaped areas so that they fit perfectly. This includes around doors, windows, plumbing, and electrical. Take note, it is important to wear eye, breathing, and body protection when working with fiberglass batts.

To learn how to cut fiberglass batts, take a look at this post: How To Cut Rolls Or Batts Of Insulation

Blown Loose-Fill Insulation

Loose-fill insulation is an option for adding insulation to existing walls without the requirement of an extensive demolition and/or remodel. In fact, this is the best option for adding insulation to existing closed cavities anywhere in your home.

Click here for loose-fill insulation from Amazon.

Loose-fill insulation comes in many types but is most often either made of fiberglass or cellulose. Cellulose is slightly more expensive but also has a higher R-value per inch. Thus, for most homes, cellulose is the best choice.

One advantage of loose-fill insulation is that it will fill your wall bays no matter the size. Thus, the same type of insulation and installation technique is appropriate for both 2x4 and 2x6 walls.

To learn more about loose-fill insulation in walls, read this article: Can You Use Loose Fill Insulation In Walls?

How to Add Loose-Fill Insulation

Loose-fill insulation is blown into your walls by drilling large holes in the existing outside or inside cladding. Then, the loose insulation is blown into the bays through hoses hooked up to an insulation blower.

Blown in insulation in the house attic

Care must be used to ensure that the entire bay is full of insulation, especially since it is not possible to see into this space. Generally, a hose is inserted into the hole and then slowly drawn up the bay. For broken bays, such as above and below windows, two holes must be drilled.

Afterward, the holes are patched using the originally removed rounds, caulking, and are painted to match. Take note, even when professionally done, this method will leave round marks on the siding. If you start to look around, you will be able to see these marks on the exterior walls of older homes.

It's also important to note that, to blow insulation, you will need to either rent an insulation blower or hire a professional. Often, if you buy enough insulation from a home improvement store, they will rent you the associated insulation blower for free.

A fully suited insulation technician installing blown in insulation

However, this job is generally not considered an easy one and takes one person to man the blower and another to work the wall side of the project. Thus, it is highly recommended that you hire a professional to perform this task. Either way, it is worth reaching out to a few companies for a free quote.

Spray Foam Insulation

Finally, we will consider spray foam insulation. The major downsides of spray foam are that it is expensive, difficult to install, and requires full access to the wall bays.

However, spray foam provides a high R-value per inch and also can be a complete vapor and air barrier. Also, hardened foam adds sturdiness and strength to the wall assembly.

Spray foam insulation for the attic wooden framing

While it is possible to install spray foam insulation as a DIY project, this is not very efficient for significant square footage. Rather, it is generally best to hire this project out to a professional installation company that will use high-end sprayers.

Unlike fiberglass batts, the same foam is appropriate for both 2x4 and 2x6 cavities. That being said, the larger width of 2x6 framing bays does mean that more foam is required to fill the space.

Technician spraying foam insulation on the wall

However, spray foam does come in both closed-cell and open-cell varieties. Most contractors and architects prefer closed-cell spray foam because it doubles as a vapor and air barrier and has a higher R-value per inch. However, if you want the wall assembly to be able to breathe, open-cell foam is the better option.

To learn more about applying spray-foam insulation, read this article: Can Foam Insulation Be Installed In Existing Walls?

Can you use 2x6 insulation on 2x4 walls?

Generally, you cannot. This is because it is inadvisable to compress batt insulation. Also, the only way to get 2x6 insulation into 2x4 bays is to compress that insulation. Doing this would significantly reduce the total possible R-value for that wall assembly.

Thus, if you used 2x6 insulation on 2x4 walls, you would end up compressing the batts and reducing their effectiveness. If you do have some 2x6 insulation leftover and only 2x4 walls to fill, the best call is to actually tear the thick insulation down to the thinner desired size.

How do I find the maximum R-value for a 2x4 wall?

Finding the maximum R-value for 2x4 walls is a relatively simple process. First, investigate the R-value of common wall insulation. A Google search shows that closed-cell spray foam has the highest R-value per inch with a value of R-6.5 per inch.

Now, we know that 2x4 walls are 3.5 inches thick. Thus, all we need to do is multiple 3.5 inches by R-6.5 per inch to get a total maximum R-value of R-22.75. You can use this method to calculate the R-value of any thickness of assembly and insulation.

Is R-13 insulation good?

For 2x4 walls, according to the International Code Council, R-13 is considered a pretty good insulation level. In large part, this is because it is difficult and costly to add insulation to 2x4 walls of a higher R-value.

Can You Use Rigid Foam for Walls?

It is possible to use rigid foam for walls. However, this insulation type is quite expensive per square foot and difficult to properly install. Therefore, only consider using rigid foam insulation in walls if you already have the material on hand or are very familiar with the installation procedure.

In Closing

Wooden framing of a house with spray foam insulation, What Insulation To Use For 2X6 And 2X4 Walls

In this post, we answered the question of what type and size of insulation to use for both 2x4 and 2x6 walls. To accomplish this, we provided a rundown of the pros, cons, techniques, and considerations for the primary types of insulation for residential walls.

To close the post, we answered several questions related to this topic. Good luck!

Leave a Reply