Foam Board Insulation

Although foam board insulation is a more expensive alternative to other insulating materials, such as fiberglass or cellulose it’s still used in places where space limitations are encountered. Another reason why foam insulation is preferred over the aforementioned ones is because of it’s high R-values, ranging from R-4 to R-8 per inch of thickness being almost 3 times greater than most other insulating materials of the same thickness.

Foam insulation is usually made with one of three different insulation materials such as: molded expanded polystyrene (MEPS), extruded expanded polystyrene (XEPS) or polyurethane, polyisocyanurate, or a related chemical mixture. Some can be installed as a liquid while others come as factory made panels called technically called foam insulation board.

Molded Expanded Polystyrene Foam Insulation Board

Or MEPS as it’s commonly called is a closed-cell material that can be easily molded into various everyday items, such as coffee cups and shipping materials or into large sheets as construction insulation. The MEPS or ‘beadboard’ has an R-value of about 4 per inch of thickness, which is a pretty good value.

The Beadboard for roofing insulation has to be dense enough to be able to walk on without damage. Wall foam insulation boards are way less denser than roof boards, their R-values ranging from 3.8 to 4.4 per inch of thickness.

Extruded Expanded Polystyrene (XEPS) Foam Insulation Board:

XEPS as it’s commonly called is also a closed-cell foam insulation similar to MEPS although XEPS is more expensive than MEPS it has a higher R-value, an R-5 value to be more precise and is also more consistent and has a higher compressive strength than MEPS. XEPS is best suited for roof or wall foam board insulation. Another factor that makes XEPS better than MEPS is the fact that it has an excellent resistance to moisture absorption.

Polyurethane and Polyisocyanurate Foam Insulation Board:

Both of the above mentioned types are available as a liquid spray, poured foam and also as a rigid foam insulation board. The advantage of using Polyurethane and Polyisocyanurate Foam Insulation Boards is that they can be made into laminated panels with a variety of facings .

Over time, the R-value of the foam drops as some of the gas escapes and air replaces it. This phenomenon is known as thermal drift. When manufactured, the initial R-value is roughly R-9 per inch. Experimental data on this type of foam indicates that most thermal drift occurs within the first two years after manufacture and slowly decreases until it stabilizes at about R-7 per inch. It then remains unchanged unless the foam is damaged.