How To Insulate A Vaulted Ceiling

A common question that comes up with vaulted ceilings is how to install insulation in them. Why? Because these ceilings are known to pose a unique challenge when it comes to laying insulation. We've researched best practices and methods for insulating vaulted ceilings, and in this post, we will share them with you.

Here are a few best practices to remember when insulating vaulted ceilings:

  • Inspect the space and determine insulation thickness
  • Plan for moisture issues
  • Consider outside Insulation
  • Install the insulation properly
  • Wear the proper protection

It's essential to know how to insulate vaulted ceilings to prevent the insulation from falling and becoming inefficient. Throughout the post, we'll cover best practices and the most popular types of insulation to use on these types of ceilings. Continue reading to learn more about the best ways to install insulation in vaulted ceilings.

A cozy and warm rustic log cabin with brick mantled fireplace and a huge rug under the furniture's, How To Insulate A Vaulted Ceiling

Best Practices for Insulating Vaulted Ceilings

Inspect the Space and Determine Insulation Thickness

The height of cathedral ceilings makes it necessary to insulate them properly. If not, you may find yourself with a pretty drafty home, even in the warmer months. Often the issue is these ceilings will leave little room for insulation between the roof boards and the ceiling itself, so you'll need to do a close inspection of the ceiling to determine what thickness and type of insulation will work best.

When it comes to the thickness of the installation, there will be certain requirements depending on the region in which your home is located. This is required regardless of whether your using fiberglass, cellulose, or open-cell spray foam for your ceiling. Colder regions, such as the east coast and northern states, typically require insulation with a higher R-value, R-40 to R-60. You can visit the U.S. Department of Energy website to find the recommendations for your area. It's also best to check with local municipalities to see if you need any permits and ensure that your home needs any building codes required by your locale.

The inner working of a building with vaulted ceiling

Plan for moisture issues

Heat flow and moisture are the most significant things you need to deal with when insulating vaulted ceilings, so it's important to plan for them. If not, you may find that the roof experiences freezing and layers of ice. This will eventually cause the roof to leak. As a result, the leaking can lead to problems such as mold and rot. Most contractors will typically leave a sufficient amount of air space beneath the roof deck and then install air vents at the ridges to help get rid of moisture.

Install the insulation properly

More often than not, you'll find that contractors will typically use batt insulation to insulate vaulted ceilings. If the space is big enough, you should be able to install the batts right on top of the rafters in the ceiling. Remember, there must be at least 2 inches of breathing space between the roof sheathing and the insulation for efficient ventilation. It's important first to measure the distance between the rafters and the trusses.

You can multiply the number of spaces that need to be filled by the truss length to do this. This will help you determine how many batts of insulation you'll need (if you're installing it yourself).

When rolling out the insulation, measure each piece and then cut them to the width of the rafters. It's also a good idea to keep a utility knife or electric saw hand for on-the-spot cutting as well. Also, when pressing the batts into their position, be sure not to cram them into place to the point where they are densely compressed. Doing so will reduce the R-value of the insulation. When stapling the insulation flanges to the truss bottoms, make sure the insulation is snug.

Also, prepare to cut around electrical outlets and light sockets. The best way to do this is to save your scrap insulation and trim it to fit around these gaps and small spaces. You'll also want to account for any recessed lighting that the ceiling may contain. This means becoming familiar with the building and fire codes in your locale. So make sure that you perform all due diligence before head to ensure that you're taking the right safety precautions.

Wear the proper protection

It's important to wear the proper protective gear when insulating vaulted ceilings, just like other ceilings. Protective gloves, pants, long sleeves, and a ventilator mask are essential when working with insulation, especially if it's made of fiberglass. Also, if you have to do any structural work when installing the installation, such as adjusting or installing joists, always be sure to wear a safety helmet.

Check out this safety suit on Amazon.

What is the best insulation for a vaulted ceiling?

Interior of a modern rustic designed living room constructed using wood from ceiling to flooring

Most home contractors would probably tell you that the best insulation to use for a vaulted ceiling is fiberglass insulation. The main reasons are that fiberglass is one of the most inexpensive types of insulation that you can purchase, and fiberglass batts are relatively easy to install in vaulted ceilings.


To install fiberglass insulation, you'll need to staple the batt to the underside of the ceiling. It's best to install the insulation before you install any drywall in the room. Fiberglass is also reasonably easy to cut, and you can use a utility knife or saw to make sure that it fits into every nook and cranny of the ceiling so that there are no voids that may allow warm air to escape.

On the other hand, the biggest downside to fiberglass insulation is that it can trap dust, allergens come, and moisture. This can lead to mold growth, and the insulation may also start to sag over time, especially if it becomes wet.


The second best insulation to use on vaulted ceilings is cellulose insulation. Although cellulose can be tricky to install on vaulted ceilings, it's very effective at keeping warm air in and keeping cold air out. However, it is crucial to make sure that your contractor is familiar with installing this type of installation on vaulted ceilings, as they cannot apply it wet without stapling a mesh screen to the roof's trusses beforehand-which prevents the insulation from dripping down.

Cellulose has an advantage over fiberglass batts in that it can easily fill up small crevices, nooks, and crannies in the ceiling. It's usually made of recycled materials and is sprayed with multiple chemical treatments to make it resistant to mold, fire, and pests. On the downside, cellulose can settle up to anywhere from 15 to 20%, which can be more problematic with vaulted ceilings. It can lead to sufficient air leakage and potentially higher energy bills.

Should I put a vapor barrier on my ceiling?

Whether or not you need to install a vapor barrier on your ceiling depends on the climate in which your home is located, the structure of your home, and the layout of the ceiling. Vapor barriers should only be installed when an attic has proper ventilation and if the average temperature of your region is on the cool side.

Installing vapor barriers in regions with hot, dry climates is not ideal. They can cause excessive heat to accumulate in the attic, especially if the attic is not vented. In these environments, there isn't enough moisture available in the air to justify installing the barrier. It's best to ensure your home has controlled mechanical ventilation and proper barriers are installed instead of vapor barriers--regardless of the local climate.

What is hot roof?

"Hot roof" is a term used when attics are sprayed with foam insulation to increase the temperature on the underside of the roof. This is usually because ventilation is not present. The benefit of the system is to increase the temperature within the attic so that when the attic is warm, the interior of the home or building will be easier to keep warm.

The term is a misnomer, as the roof itself is not "hot." The insulation in these unvented attics helps prevent ice dams from building up on the roof with can a term save you money and prevent hazardous outside conditions during the colder months.

Does a vaulted ceiling need ventilation?

Interior of a living room with vaulted ceiling

Most roofers would agree that a vaulted ceiling should have ventilation. The most common types of vent you'll see on these types of roofs are rafter, ridge, and intake vents, in addition to vented truss vents.

Wrapping Things Up

We hope that this post has helped you better understand how to install insulation on a vaulted ceiling and the best practices involved with doing so. It's always best to consult with a licensed contractor before performing any home insulation project to ensure that you implement the correct practices for your safety and proper installation.

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