Make Sure You Properly Ventilate Your Foam Insulated Roof

Posted on: 28 September 2015


If you plan on using foam to keep your roof insulated, you need to make sure that there is enough air circulation around your foam insulation. You need to allow air to move around your foam insulation in order to keep moisture from building up. Here is what you need to do to keep your roof well insulated and well ventilated.

Secure Sheathing Over Your Rafters

If you are just building your roof, you will need to secure sheathing material over the top of your rafters. If you are redoing the insulation in your roof, you will want to make sure that sheathing material is in place; if not, you'll want to do this step, too.

You should install sheathing material that is around an inch thick in order to provide the highest level of insulation. Make sure that you leave about a one-inch gap near the ridge of your roof for air to escape.

In order to make the gap look more uniform and in order to make sure the gap stays stable, you should install a plastic ridge cap between the sheathing and the top of your rafters.

Install Temporary Long Plastic Forms

Next, in order to space the foam out correctly, you'll want to install long plastic forms to your rafters. These long plastic forms can be found at your hardware store and are generally about an inch thick. They allow you to create a space in between the foam insulation and your rafters and are designed to run the entire length of your rafters.

Most are made to just be wedged into place; you don't have to hammer them into place. You'll be removing them later, so it is essential that they are easy to get out.

Spray The Foam

Next, you will need to spray the foam insulation between your rafters. The long plastic forms you installed will provide you with air flow later on when you remove them. Make sure you follow the instructions for the spray foam; you'll want to work left to right, top to bottom, filling in the area between your rafters with foam.

You should also wear safety goggles and gloves while spraying the foam to keep yourself safe.

Form The Foam

If any of the foam extended the boundaries of your rafters, you can cut away any extra foam with a saw. A saw will allow you to quickly cut away any excess foam.

Once the foam has dried and set according to the packaging instructions, you'll want to pull out the plastic forms. Once the plastic forms are removed, there will be space around the insulation for air to circulate. This will help prevent moisture from building up inside of your attic.

When adding foam insulation to your roof, make sure you build in a little breathing room so that you get the insulation and ventilation you need at the same time. If these instructions seem daunting to you, don't hesitate to hire a roofing company to install the insulation for you.