Installing rigid flat roof insulation

This is a job that you can do on your own. Flat rigid foam boards work best for exposed ceilings. They are great when it comes to energy savings.

First of all you will need to get some tools. You can even rent them from your local hardware store.

Tools and materials:

  • Rigid foam board insulation
  • Plastic
  • Staple gun
  • Spray foam
  • Tape measure
  • Utility knife


Take some measurements before you start cutting the foam. Measure the space between the joists to see how wide the foam needs to be.

Cutting the foam

Use an utility knife to cut the foam. Help yourself with a straight edge. Then use the knife to cut the foam.

Joists foam

Use a ladder to reach the ceiling. Install a 2 inch foam layer between the joists. The size of the foam can differ a lot, and if the space in your ceiling is quite large, you can install even thicker foam.

The joists should hold the foam in place. Leave not empty spaces.

Spraying foam

To create an air tight seal, you will need to add some spray foam. Spray it on every edge. It will also better fix the foam strips. You can use caulk instead of spray foam. But do try to avoid this as you won’t get the same effect.

Adding plastic sheeting

Now, after you have applied the spray foam, you will need to add some plastic sheets on the wall. Staple the plastic directly to the joists. Start from one corner and continue to the entire room.

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