Foam board insulation is a rigid sheet of insulation that is becoming popular with insulation contractors and can be used in almost any part of the home. This type of home protection provides good thermal resistance and, in some cases, can add structural strength. When used as sheathing these insulation panels reduce the conduction of cold or heat through both wood and steel studs.
Traditional forms of insulation, such as fiberglass batts and blown-in cellulose, are less expensive and so always have dominated the insulation market for new home building. The thick wall spaces of new wood-frame homes, besides giving structural integrity, also enable the home to achieve an insulation value of between R-20 and R-25 using either fiberglass batts or blow-in cellulose. Although more expensive rigid foam board insulation has more advantages:
- Moisture-Proof: Fiberglass batts and blown-in cellulose can absorb moisture which can the negate much of their insulation effectiveness. Besides replacing the air pockets, lowering the R-value, moisture causes the materials to settle leaving spaces at the top of the walls. Foam does not deteriorate upon contact with moisture and holds its shape and insulation factor.
- Resists Insects and Rodents: Because of its make-up foam does not promote a great habitat for either insects or rodents, vermin that can easily burrow through the other types of insulation and make nests. This channeling also produces drafts.
- Convection and Conduction: If not tightly-fitted into the wall spaces traditional forms of insulation can leave small gaps than can allow cold air from the outside to form channels into the wall. This cools down the interior walls and increases the energy needs of the home.
- Mess: The traditional forms of insulation are messy to install and the installer requires protective equipment. With rigid foam board there are no safety requirements.
There are three (3) main types of foam board insulation and each has its own uses:
1. Molded Expanded Polystyrene Foam Board
MEPS, or molded expanded polystyrene, is a closed-cell foaming material that is used in many common items such as coffee cups and padding for shipping. It is also made into large sheets of rigid foam board insulation commonly called beadboard. Beadboard is manufactured by mixing loose, polystyrene beads containing liquid pentane with a "blowing agent" into an enclosed mixing container. This mixture is then heated whereby the beads expand to many times their original state. These beads are then injected into a mold and subjected to more heat plus pressure. Under these circumstances they expand into the needed shapes.
MEPS foam board varies with the densities of the beads and this depends on where they are needed. For example, beadboard material for roofing has to be strong and dense enough for a man to walk on without falling through the ceiling. Wall insulation foam boards do not need to be as strong so are manufactured several times less dense than the roof panels. Since the beads are more loosely packed the board has a better R-value, ranging from 3.8 to 4.4 per inch of thickness. This gives a wall a similar or better R-vale than fiberglass batts or blown-in cellulose insulation.
MEPS foam board is also available with a variety of finishes and is used exclusively in structural insulated panels (SIPs) and insulated concrete forms (ICFs).
2. Extruded Expanded Polystyrene Foam Board
Like MEPS, extruded expanded polystyrene, or XEPS, is a closed-cell foam insulation. It is manufactured by mixing polystyrene pellets with various other chemicals in a liquid form. By injecting a blowing agent into the mixture this forms gas bubbles in the liquid and produces a foaming mass. This liquid foam is then forced into a mold or extrusion die for shaping, as it is for a foam panel. Once it is cooled the panel is cut into the required sheets.
Because of the chemicals involved, extruded expanded polystyrene foam board is more expensive than MEPS. And just like MEPS the density of the foam material will decide the R-value, which is usually about R-5 per inch in most brands. Its consistent density and high compressive strength makes it well-suited for structural use. The other advantage it has over MEPS is that it has s greaster resistance to the absorption of water. However, like MEPS, extruded expanded polystyrene is available in a variety of facings and is used as the insulation portion for SIPs and ICFs.
3. Polyisocyanurate and Polyurethane Foam Board
Two other rigid foam, closed-cell insulation types, polyisocyanurate and polyurethane, also offer high R-values. They are so high (R 5.6 to R 8) per inch of foam board thickness, that a thinner panel can achieve the thermal resistance of a much thicker XEPS or MEPS board. Although this is may not be important in normal circumstances it is a great advantage when there are space limitations.
Polyisocyanurate and polyurethane foam panels are available in a wide variety of compressive strengths. This allows them to resist warping and deformation and so it can maintain its shape under a high wind force or heavy load. They also can remain stable in both abnormally low (-100ºF) to high (+250ºF) temperatures making them great for roofing insulation.
For more information on foam board insulation consult our Contractor Directory or simply post your project online.
Posted by: TrustedProsSuggested Reading For You
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