How To Insulate A Vaulted Ceiling

One of the most common questions we get asked is how to insulate a vaulted ceiling. Insulating any ceiling isn’t easy, but chuck in the added difficulty of the ceiling being vaulted, you need to be sure of what you’re doing before getting started.

In this post, you’ll learn about the best practices to install a vaulted or cathedral ceiling and the type of insulation to use. 

Vaulted ceiling insulation

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Considerations Before Insulating Your Vaulted Ceiling

First off, you need to consider some factors before insulating your vaulted ceiling. They include:

  • Doing a thorough inspection and confirming what insulation thickness you will require
  • Keeping outside insulation in mind
  • Considering moisture issues
  • Using protective wears
  • Your ability to install the insulation, or if you need to hire a professional

If you’re going to tackle the job yourself, you’ll need to ensure you’re confident in doing so, which will include being up a ladder, so safety measures will also have to be taken. 

What Type Of Insulation Should You Use On A Vaulted Ceiling?

Fiberglass insulation is the best insulator for a vaulted ceiling. This is because they’re the most affordable and their batts are easy to install.


When installing fiberglass, be sure to staple the batts to the lower side of the ceiling. Make sure you install the installation first before other installations.

Fiberglass batts are extremely easy to cut using a knife or a saw. This makes it easy for you to fit them in any area of the ceiling so there won’t be any loopholes for air to escape.

The only issue with fiberglass insulation is they can trap dust and moisture.This can cause mold growth and even make the insulation sag.


Cellulose insulation is another great insulation you can use on your vaulted cathedral ceilings.

Installing cellulose in a vaulted ceiling is a little complicated. But it can help maintain the warm and cold air balance. However, if you are using a professional, they should know the correct way to install it.

For example, they need to first staple the mesh screen to the truss – that way, insulation won’t drip down.

The advantage of the cellulose over fiberglass is their ability to fill up every area of the ceiling. Cellulose are made out of recycled materials treated with chemical sprays. This makes them resistant to pests, fire, and mold.

How To Insulate a Vaulted ceiling

Examine the ceiling and insulation thickness

Vaulted ceilings must be properly insulated because of their height. If not, your home may become pretty drafty, regardless of the season due to the fact that heat rises, therefore it will all escape through the ceiling.

What R-value do I need for a vaulted ceiling?

You need to examine the ceiling to identify the perfect thickness and insulation.

Before starting, you must consider certain requirements when deciding the thickness of the insulation, but this also depends on your location. Colder regions like the northern states and east coasts need higher R-value insulation. Between R-40-60 is generally a good range.

Visit the official site of the US Department of Energy for the best recommendation.

Also try to check with local authorities if you’ll need permits to undergo this project.

Prepare for moisture problems

Moisture and heat flow are two things to keep in mind when insulating your vaulted ceiling, so make sure you’re fully prepared for them. 

If not, the roof may freeze or have layers of ice and may result in a leaky roof. And leaky roofs may harbor mold or even rot. 

Contractors usually try to create enough air space below the roof deck. Then they remove moisture by having the air vents installed at the ridges in the way of ridge vents or baffles.

Perform a proper installation

If you have a spacious ceiling, installing the batts should be easily done on the ceiling (on top of the rafter). However, make sure you leave at least 2 inches between the insulation and the roof sheathing as this will create more rooms for effective ventilation.

But, first off, always measure the distance between the trusses and the rafter.Better still, you can multiply the number of empty spaces to accommodate the truss length. That way, you can decide the number of batts you’ll need for the process (that’s if it’s DIY).

At the start of installation, be sure to measure each batts and cut them in accordance to the widths of the rafter. We also suggest that you have an electric saw hand and utility knife for any trimming needed on the go.

Also, when pressing the batts into the ceiling, avoid cramming them to a compression level as this will reduce the insulation’s R-value.

Be sure that you have a snug insulation before you staple the insulation flanges.

Furthermore, keep light sockets and electrical outlets in mind when cutting. You can do this by saving your old insulation, then trip it so it can be fitted around the small spaces and gaps.

It’s also your responsibility to take care of the ceiling and lighting for any issue. So you need to familiarize yourself with your local fire and building codes. That way you’ll be sure you’re not breaking any rules.

Wear protective gear

Always wear protective gear when insulating your vaulted ceiling.

You should wear your protective gloves, long sleeves, and ventilator masks and eye goggles. 

This is super important when working with fiberglass.

Always wear a safety helmet when performing structure related works like joists installation.

Does A Vaulted Ceiling Need Ventilation?

Yes, a vaulted ceiling needs ventilation otherwise it is prone to moisture getting stuck which will create mold. 

Some of the most common vents include ridge, intake vents, rafter, and vented truss vents.

Should I Install a Vapor Barrier On My Ceiling?

Installing a vapor barrier on your ceiling comes down to:

  • Layout of your ceiling
  • Your home structure
  • Climate

You should install a vapor barrier on a ventilated attic and cool temperature area.

We don’t recommend vapor barrier installation in areas with dry climates. Dry climate can cause excess heat to accumulate inside the attic. (especially if it’s not vented).

Areas with dry climates have little moisture so there’s no need to install a vapor barrier.

Final Thoughts

We hope you’re able to better understand how to insulate a vaulted ceiling, but It’s best to contact a licensed contractor to handle the entire project.

You may also be interested in how to insulate behind shiplap and how to insulate laminate flooring.