The Uses and R-Value of Foam Board Insulation
If you are planning any remodeling than includes adding on to an existing structure, you may wish to consider using foam board insulation in your construction plans.
Obviously, adding some form of insulation to an exterior wall or roof is necessary not only for saving money on heating and cooling costs, but in many cases to meet local building codes. The amount of insulation required for your project can depend a great deal on your location since many states have minimum requirements for thermal resistance.
The R-value listed for any type of insulation is a rating that refers to the resistance of the material to thermal conductivity. While the actual formula involves the temperature differential and the heat flux (transfer), for all practical purposes it is sufficient to think of the R-value as a resistance to thermal change in the same way that a resistor restricts current in an electrical circuit. To carry the analogy one step further, if you place two resistors in series the total resistance is achieved by adding their values together. The same is true of R-values in foam insulation; two thicknesses of R-4 foam board, properly installed, is the equivalent of R-8 insulation.
The R-value for foam board insulation is typically R-4 per inch, which means that one inch of insulation is approximately the equivalent of a 4-inch thickness of wood, which has a rating of R-1.
Foam board can be more expensive that other types of insulation, but is very useful in applications where space is an issue, and a high R-value is required. Space is an important consideration in planning insulation. Increasing the density of a fibrous insulator, for example, by forcing double the amount than is recommended into a given space, will not double its ability to insulate.
Applications for foam board use include roofs, exterior above ground walls, and basement walls, in which the best use is on the interior of the cinder block. Placing the foam on the interior of the basement helps to isolate it from ground insects that could bore into it, compromising its effectiveness.
It is important in to remember that when applying the foam boards, the seams must be fitted tightly together and sealed. This is to help prevent unintended circulation and thereby moisture problems within the walls.
The primary ingredients in foam insulation are generally some form of polystyrene or polyurethane. One form of polystyrene that is used is molded expandable (MEPS) polystyrene. While there are other formulations, the base materials are generally similar and exist in many forms of insulation.
Foam board is very easy to cut and shape, light, and generally easy to work with. Look into the ways foam board insulation might fit into your next home construction project.