Roof Insulation and Ventilation

insulation under roof near skylights

Attics are often considered dead space. Especially if they're underneath a roof with low insulation, they're often unpleasantly cold and musty. Depending on your climate zone, you have a range of options to control moisture and cold intrusion to lengthen the life of your home and cut energy costs.

Making sure your roof and attic are watertight, insulated, and ventilated, will help protect your home and keep utility expenses to a minimum.

Spray Foam Insulation

person in protective gear applying spray foam insulation under roof

Spray foam insulation sticks to most surfaces and expands as applied. It's hard to remove once it's been sprayed on, and it can exude fumes even after installation, so it's not a great choice for attics you'll be using as living spaces. It's also expensive to install.

On the plus side, spray insulation does tend to have a high R-value, which makes it an effective choice from a warmth standpoint.

Safety Note: Some spray foam insulation products can catch fire if improperly applied, so if you go with this option, recruit a professional contractor to install it.

Batt Insulation

gloved hand installing batt insulation squares

This is a more familiar form of insulation. It's typically manufactured from spun fiberglass, cotton, or rock wool.

Batt insulation comes in pre-cut panels, which makes it easier to work with than rolls that have to be adjusted to fit. It's also not as effective as spray foam in colder climates, but it can hold its own in the desert, and it's much easier to install yourself.


When purchasing insulation, you'll notice all kinds of numbers on the packaging but you want to look for the material's “R-value.” That number tells you how good the insulation is.

The higher the R-value, the higher the price tag and the better the insulation. Your local area will have building codes that must be followed in regard to the minimum R-value for insulation. Make sure to check on this before you spend money you can’t get back.

Attic Fans

Attics are known to be stuffy. This can be a problem for a few reasons.

For one thing, humidity can build up in your attic, even in colder times, inviting gradual moisture damage and creating dangerously supportive conditions for mildew and mold.

For another, bad air circulation in your attic will tend to drive up your energy costs. Warmer air will tend to accumulate here, which inhibits both cooling and heating.

Installing a good ventilation system in your attic will therefore help you both prevent humidity damage and reduce energy costs.

One common spot to place an attic fan is toward the peak of a roof, where it may or may not connect to a vent to the outside.

attic fan coming out side of house

Vents can also be installed on the ridge of the roof, and automatic humidity monitors can even be set up to detect excessive humidity and activate an attic exhaust fan to remove it from the attic and bring it back to a safe level.

Insulation Benefits

Without insulation to create a warm roof, the heat generated inside a home will gradually escape through the attic.

This also applies to air conditioners. These devices are forced to work harder if heat is sneaking in through an uninsulated roof, which means you're wasting money every time you run them.

So the bottom line is that good insulation is a great affordable way to cut your home energy costs over time, as well as minimize the chance of damage from sub-optimal humidity conditions.

And while you're improving your utility efficiency, here are a few more simple energy-saving ideas.