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The Real Deal with Insulating Vaulted Ceilings

14 February 2014

Vaulted, or also known as cathedral ceilings, offer a very aesthetically pleasing appearance adding a luxury of height, comfort and light into your home, but they can also pose some interesting challenges when it comes to insulation. Since you know that heat rises, vaulted ceilings in your home cause you to heat space that you can’t really feel; unless you have ceiling fans pushing that warm air back down. Here are some things to keep top of mind.

Moisture Control

In very cold climates, like ours here in Minnesota & Wisconsin, having a poorly insulated roof can cause the common phenomenon known as ice damming. The process of thawing and refreezing produces a thick layer of ice at the eaves and then water backs up on the roof and eventually leaks into your home. Not controlling the moisture in your ceiling can lead to a variety of problems including, but not limited to, mold and rotting. You want to have an air space beneath the roof deck with air vents at the eaves and ridge to carry away moisture. Watch the humidity levels in your home as the days get colder you want less humidity every time your furnace adjusts humidity levels down in your attic or crawl spaces.

What Type of Insulation?

Closed cell spray foam is the best choice for vaulted ceilings because it does not absorb water and is currently the best air sealing on the method on the market. Spray foam insulation not only insulates, but it also strengthens whatever material it adheres to. Spray foam has an amazing R-value of R-6.5 per inch, creating a very well insulated space. You can also use cellulose, Rockwool, fiberglass blankets, blown fiberglass, denim blankets and Basa Batts, just keep in mind that some air and moisture will be able to pass through these types of insulation.


You want to have optimal ventilation in your cathedral ceiling allowing air flow space between the insulation and the roof deck. Depending on where you live, it is recommended to leave some practical space for ventilation and that amount of space has been the subject of debate for years with some codes stating it requires a minimum of 1” and some say ½” will suffice. The best form of ventilation is utilizing a combination of eave, also known as soffit vents, and ridge vents for continuous ventilation allowing movement of air and minimizing moisture problems, which will in turn prolong your roof life.