How To Install Rigid Foam Insulation Between Studs

By Dan WienerLast update
How To Install Rigid Foam Between Studs

Installing rigid foam insulation throughout your home is one of the most effective ways to keep the house warm during those frigid winter months. The best part is that it’s an easy enough process that any enthusiastic DIY homeowner can handle should they want to do so. However, if you feel as though it will take up too much time or you aren’t confident in your skills, it’s best to have a professional contractor handle it for you.

The ideal method of installing rigid foam insulation is to simply run the 4X8 footboards throughout the wall making the foam an integral part of it and nailing them to the house framing. That, however, does not mean there aren’t other methods that can be used. Learning how to install rigid foam insulation between studs might go slightly against the norm, but it’s possible and quite easy to do.

Read on to find out more!

Step-By-Step Guide On How To Install Rigid Insulation Between Studs

It should be noted that installing rigid foam board insulation is best used in below-grade applications. These are places such as basements that tend to have a bit of moisture. That being said, here are the steps you need to take to install rigid foam boards as insulation in your home.

Step 1: Accurately Measure The Work Area

You will need to measure the project area accurately to know how much foam board to buy for your wall insulation. One mistake that many DIY enthusiasts installing rigid foam as insulation make is subtracting studs. Do not do that – if the wall measures 40 feet long by 8 feet high, the total area to cover should be recorded as 240 square feet. That’s how much rigid foam you need to buy.

Step 2: Accurately Measure Each Bay Width

When dealing with a stud wall, it’s understandable to assume that they will be placed at an average distance of 16 inches on-center. The problem with this is that it isn’t always the case. Sometimes, you will find them at 15 inches on-center or just slightly off.

If you assume that the studs are 16 inches on-center, then the bay width for the stud wall will be approximately 14 inches. All things remaining constant, sizing your rigid foam to these figures will give you an excellent fit that is not too tight, nor is it oversized (oversized rigid foam insulation is notoriously difficult to resize by shaving it down).

However, since not all studs will conform to the 16 inches on-center rule, measuring each bay separately and accurately recording each measurement is important. For example, you will want to have them written down like so:

  • Bay 1: 16 inches by 8 feet
  • Bay 2: 15 1/4 inches by 8 feet
  • Bay 3: 17 inches by 8 feet

This gives you the right figures to work within the next step.

Step 3: Cut The Rigid Foam To Size

Once you have the accurate measurements, it’s time to cut the rigid foam sheet to size. Simply take your drywall square for the measurements, Sharpie for the markings, and ordinary wood saw for shaving the rigid foam down. Remember to mark them down per the above measurements (Bay 1,2,3…)

Step 4: Install Each Rigid Foam Board In Its Corresponding Bay

Start placing individual foam boards in their respective bays. If the measurements were correct, these sheets should fit snuggly into the bays. That fit should be just tight enough but not too tight. If you realize that the edges of the foam sheet boards are tearing, you need to take them down and shave them a bit off before putting them back into the bay.

Step 5: Seal The Seams

No matter how accurately you measure the insulation boards and cut them, there will be some gaps between the foams and studs. These gaps, if not sealed, will render all that you have done ineffective as they are prone to air leaks. Therefore, you need to seal the insulation board with something as effective as a low-expanding spray foam sealant.

Why Use Rigid Foam Between Studs?

To some, this might seem like a lot of work, while options such as spray foam insulation seem simple and much more efficient. There are, however, several good reasons why using rigid foam insulation between studs in a wall cavity is a great idea. These include:

Image Source: JPLDesigns

Pros Of Installing Foam Board Between Studs

  • Rigid foam is very cost-effective compared to spray foam insulation that can be quite expensive when installed by a professional company.
  • Rigid foam is a good option for people who don’t have very high insulation needs. You can use this kind of material when and where needed.
  • It’s an ideal system that allows your wall to remain intact, especially if you already have a well-established wall with studs. There would be no point in upending the entire stud system just to run a continuous layer of rigid foam board insulations while you can simply cut the boards to size.

Unfortunately, just as there are advantages to installing foam board between studs, there are some disadvantages that come with it as well.

Cons Of Installing Foam Boards Between Studs

  • The work requires precision since you will be cutting up multiple pieces of foam board to different sizes.
  • There will be incidences of thermal breaks as these rigid foams, no matter how well they fit, still allow wood studs to transmit some cold into the room.
  • As the wood studs expand and contract, cracks will begin to appear, making the insulation less efficient in time.

As you can tell, installing foam insulation between studs isn’t as complicated as it might sound; it’s just a bit more tedious. It is, however, cost-effective, and quite efficient when done correctly. The steps above will help you learn how to install rigid foam insulation between studs properly.