Any time you need to insulate an area of your home or office, you will need to weight the pros and cons of foam insulation board against those of styrofoam insulation. Insulation in walls and ceilings is important both to keep warm or cool air in, depending on how your inside temperature compares to the ambient temperature outside. Proper evaluation of your insulation options before you begin your project will give you peace of mind that you have made the right decision when it comes time to weatherproof your home or office.
Foam Insulation Board
Foam insulation board, also known as polyisocyanurate insulation, is made by mixing together polyether and isocyanate that then close together to form what is referred to as closed cells. These closed cells have much in common with polyurethane in terms of chemical makeup and physical appearance, but with the added benefit of improved insulating properties. Polyisocyanurate insulation (PIR) is both smoke and fire resistant, and maintains functionality at a higher range of temperatures than standard styrofoam insulation. The ease of installation for polyisocyanurate is often higher both because it does not require a thermal moisture barrier before installation and because it is available in two different forms--liquid spray and rigid foam board similar to conventional styrofoam.
Styrofoam insulation, typically coming in large, blue panels, is the traditional form of insulation that has been used in modern times for insulating buildings. It is typically available in various thicknesses ranging from 3/4 inches to 3-inches. Since styrofoam insulation will deteriorate if it is exposed to moisture, a layer of plastic sheeting must be installed before styrofoam insulation can be installed. Styrofoam insulation is more prone to drafts and air seepage than sprayed polyisocyanurate insulation due to the fact that individual styrofoam panels must be placed next to one another, often leaving gaps in insulation. One of the most obvious benefits of traditional styrofoam insulation is that it is relatively easy to work with and can be cut easily with a utility knife.
The insulating potential of all types of insulation is measured in a figure called an R-Value (resistance to heat flow). The higher the R-Value of insulation, the greater its ability to prevent heat transfer. Typical R-Values for different types of insulation can range anywhere from R-3 to R-15, depending on a number of different variables. Immediately after installation, polyisocyanurate insulation will typically have an R-Value right around R-9. As the insulation settles and air begins to form in pockets (usually within the first two years after installation), this number will settle around R-7 or R-8 and remain there permanently.
In comparison, the R-Values of traditional styrofoam insulation will vary greatly depending on a number of different variables. 3/4 inch styrofoam insulation will typically produce an R-Value of around R-3.8, while 3-inch thick styrofoam insulation will produce R-Values approaching R-15. Remember, however, that gaps in styrofoam insulation will often reduce the effectiveness of the insulation installed by allowing air to seep in through gaps in the styrofoam panels.