How to Install Rigid Foam Insulation under Metal Roof?

These days, a metal roof has become a popular choice in the United States, known for its durability and cost-effectiveness compared to shingles. However, even with these benefits, it’s important to remember that such a roof requires proper insulation.

One effective option is rigid foam insulation, which can be complemented with spray foam insulation for enhanced energy efficiency and air leakage control.

Some people consider installing rigid foam insulation under the metal roof as a roof insulation solution, often weighing it against other types like spray foam insulation. Is it a nice choice?

We’ll explore the answer in this article below, considering factors like thermal resistance, vapor barriers, and the pros and cons of different insulation types.

How to Install Insulation under Metal Roofing?

Since many people install the insulation themselves rather than hiring a pro, you also may consider installing rigid foam insulation under a metal roof all by yourself.

While this is a feasible home improvement project, it’s important to understand the process thoroughly, including how to achieve a friction fit between the insulation and the roof structure for optimal performance.

rigid foam insulation under metal roof

Installing rigid foam insulation for a new roof

If your roof is new, then you can do these procedures below:

  1. Grab plywood and install it as the roof sheathing. Place it perpendicular to the joists and fasten the plywood with some roofing nails.
  2. Prepare your building paper, and place it layer by layer over the sheathes. Make it overlap by around six inches. To fasten it, you can staple or use nails. The building paper will help you protect the sheathes from moisture and leaking.
  3. Over the roof surface, particularly if it’s a standing seam metal roof, install the foam board insulation you have already prepared. You can place them close together yet ensure they don’t overlap each other to maintain effective insulation.
  4. After you’ve done the placing, use duct tape to seal the seams. This will make sure no leaks or moisture will get through the foam.
  5. Finally, as instructed, you can install the metal roof panels over the insulation.

Read also: Attaching the Rigid Foam Insulation Between Studs

Rigid Foam under Metal Roof

To install rigid foam insulation on an existing roof, you will need either to remove the current roof or place it underneath your plywood sheathing. If both of these methods feel too difficult for you, then you can consider using other insulation, such as fiberglass batts or spray foam insulation.

Each type of insulation has its own set of pros and cons, and the choice often depends on factors like the existing structure and desired energy efficiency.

Installing Rigid Foam Board Insulation for a New Roof

Reach your attic and do these procedures as follows:

  1. From the attic, try to find the plywood sheathing supported by its frame system. There are two types of beams: the large and angled one is called joists, while the horizontal one is called a purlin.
  2. Find any gaps between the purlins and the sheathing. Then, place the fiberglass batts into the gaps.
  3. The insulation will be less effective when packed tightly, so you must consider placing the fiber batts loosely into the spaces.
  4. Now, you can cover the wider span of the sheathing using rigid foam insulation. You’ll need to cut the panel into the right size required and attach the panel to the place using adhesive or staples.

Why use rigid foam as insulation for your metal roof?

Just as when you use other kinds of insulation, you will encounter advantages and disadvantages when using rigid foam insulation. The details will be as follows:

Read also: How to Install Rigid Foam Insulation under Metal Roof?

Advantages of rigid foam :

  • The closed-cell foam’s R-value is much higher than batt insulation, indicating superior thermal resistance. The R-value is a value in which a type of insulation can resist heat flow. The better the R-value, the better the material to keep the heat inside the room.
  • Since the material is way denser than other insulation options, you can reduce the chance of air leakage.

The drawbacks of rigid foam :

  • You need to fit the insulation tightly to achieve the best insulation feature.
  • With that in mind, you need to seal or tape the joints to stop the heat transfer from occurring.
  • If exposed to the UV rays, the rigid foam can be damaged.

Using rigid foam board under a metal roof not only provides effective insulation but also acts as a vapor barrier, protecting against moisture. This makes it ideal for those looking to enhance their building’s energy efficiency.

Combined with spray foam insulation, it can improve the building’s thermal performance and reduce energy loss.

So, those are some information you need to know about rigid foam insulation under a metal roof. Hopefully, this information will be beneficial for you.

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Insulator is a skilled author and Insulation expert with years of experience in the field. He has authored several articles and books on various aspects of insulation installation, maintenance, and repair.