Do you need a vapor barrier with rigid foam insulation?

Do you need a vapor barrier with rigid foam insulation?

5 Answers. Rigid foam insulation is usually a qualified vapor barrier. However, an installation between the studs can pose a challenge. To complete the vapor barrier you would want to foam-seal or tape all the sides where the rigid meets timber, because these gaps will facilitate vapor flow.

Does rigid foam insulation need to be covered?

Rigid foam insulation, whether it is expanded or extruded polystyrene, does have to be covered if it is installed in the interior of a building. This wall covering must have a minimum fire rating to protect the insulation from quick combustion during a fire.

How do you install rigid foam insulation between rafters?

Cut AP Foil-Faced foam sheathing to fit snuggly between the rafters. 2. Install AP Foil-Faced foam boards between rafters, directly against the bottom of the roof sheathing. The R- value of the insulation must meet local building code requirements for unvented attics to prevent condensation.

How thick should foam board insulation be?

Foam board insulation is easy to use and is a great DIY way to add some insulation. It comes in standard-size 4×8 sheets, and smaller sizes, in many different thicknesses from 1/4 inch to 2 inches.

Can you drywall over rigid insulation?

But rigid foam has a drawback — it's combustible, meaning it catches on fire easily. To combat this problem, drywall is required to cover it. Drywall, which is actually a mineral called gypsum, resists fire. … The most common way to hang drywall over rigid foam insulation is to glue and screw it into place.

Is rigid foam insulation mold resistant?

All rigid foam insulation is mould and mildew resistant. It won't hold moisture, even if you had a flood in your basement. … Make sure your contractor uses an adhesive that is rated for foam when they're gluing the foam to your basement walls and floor. If it isn't, it can ruin your insulation.

What is the highest R value for a 2×4 wall?

Fiberglass vats are the standard insulator for 2-inch by 4-inch wall framing, and are rated R-11 through R-15. In order to achieve the higher insulation R-value of R-21 a different type of insulation will be required.

Can I use rigid foam insulation in attic?

When used as attic roof insulation, rigid foam can be installed between attic rafters, directly beneath attic rafters, or in both locations. Like spray foam, rigid foam provides an air and moisture barrier as well as high R-value insulation.

Is rigid foam insulation better than fiberglass?

In contrast to rigid foam, fiberglass is soft and flexible. The millions of air pockets in fiberglass insulation provide a superior thermal barrier but fiberglass can also trap moisture, leading to mold and mildew growth. … Unfaced batts or rolls are the better choices for laying as an insulating "blanket."

How do you install rigid foam insulation on interior walls?

The correct method of using rigid foam is to run continuous 4-foot by 8-foot sheets of the foam across the concrete basement wall, making the rigid foam the de facto wall. After that, thin furring strips are installed on top of the foam to provide a firm base for the drywall screws and drywall.

What insulation has the highest R value per inch?

Vacuum insulated panels have the highest R-value, approximately R-45 (in U.S. units) per inch; aerogel has the next highest R-value (about R-10 to R-30 per inch), followed by polyurethane (PUR) and phenolic foam insulations with R-7 per inch.

How do you install rigid foam insulation on wood?

R19 in a 2×6 wall does not really give you an R19 wall. It is about a R16 wall because of the feect of the “thermal short circuiting” through the studs. If it is a 6″ steel stud wall, it could be as low as an R11 wall.

How do you seal foam board?

Mr. Holladay once wrote of rafters, “Yes, you can combine rigid foam and spray foam if you want to save some money.

How do you speed up foam board insulation?

It's a good choice for thin walls and for insulating garage doors. If you're turning the garage into living space or a full-time workspace and want to insulate the floor, one option is to use rigid foam covered in plywood or other subfloor material.

How can I insulate my walls without sheathing?

A second option for insulating a wall with no sheathing is to use spray foam. Polyurethane foam has the added benefit of sealing air leaks, but you shouldn't consider installing it directly against the back of the siding.

What is foam board insulation used for?

foam board insulation. Foam boards – rigid panels of insulation – can be used to insulate almost any part of your home, from the roof down to the foundation. They provide good thermal resistance and often add structural strength to your home.