Rigid Foam Board Insulation

Foam board insulation is relatively better than other types of insulation because of its high R-value (resistance against heat flow). Different parts of a building can be insulated using rigid foam board insulation. Foam board finds its application in curtain walls, roofs, foundations, entry and overhead garage doors, pipes and tanks; apart from being used between studs on interior and concrete walls. Roofs and ceilings are also insulated through this method. The R-value of the insulation differs according to the thermal resistance of different materials. Polystyrene, polyisocyanurate or polyiso, and polyurethane are the common materials used for rigid foam board insulation. Here is a brief information on each of these materials and installing foam board insulation.

Molded Expanded Polystyrene Foam Board (MEPS)
Molded expanded polystyrene foam board (MEPS) is a closed cell material, commonly known as beadboard. It requires extreme heat and pressure to be molded into items like coffee cups, shipping materials, etc. These bead boards are manufactured by mixing unexpanded foam beads (containing liquid pentane) with a blowing agent and poured into an enclosed container. The mixture is then heated at a controlled temperature (93.3^oCelsius) to expand the beads to about 30 times their original size. These expanded beads are then injected into a vacuum mold wherein they are subjected to more heat and pressure. This results in their expansion to foam blocks (about 1.2 x 5 meters x 0.76 meters tall). Thereafter they are cut and shaped according to the required size.

For insulating roofs, denser MEPS or beadboards are recommended as they would have to withstand the pressure due to walking. Beadboards that are utilized for wall insulation, are less denser than the ones used in roof. Flow of water through the beadboards may create various problems, so a vapor diffusion retarder (materials that inhibit the movement of water vapor) should also be installed. Here, R-values range from 3.8 to 4.4 per inch of thickness.

For roofs and low walls which are prone to unfavorable moisture related problems; extruded expanded polystyrene (XEPS) is preferred due to its higher density as compared to MEPS. They provide excellent resistance to moisture absorption and consistency in density and it's best suited for roof and wall panels.

Polyisocyanurate or Polyiso Foam Board
Polyisocyanurate or Polyiso is a thermosetting type of plastic, that is manufactured from closed cell, polyisocyanurate rigid foam sandwiched between two facers. The high thermal resistance of this material is due to the presence of a low-conductivity gas (HCFC – hydrochlorofluorocarbons) in the closed cell . The R-value goes from 5.6 to 8 per inch which is higher than MEPS. Polyisocyanurate insulation is available as liquid, spray foam and rigid foam board. They can be made into laminated insulation panels with variety of facings, including metal oil, plastic, paper, or plywood.

Due to thermal drift ; a condition where the low-conductivity gas gradually escapes and is replaced by ambient air, a fall in the R-value is noted. The R-value is an important factor in polyisocyanurate foam panels. It can be stabilized by using foam and plastic sheet facings.

Polyurethane Foam Board
Similar to polyisocyanurate or polyiso foam board, polyurethane foam board is also a closed-cell insulation material which contains the HCFC low-conductivity gas in its cells. These boards are also available in liquid sprayed foam and rigid foam board.

Rigid polyurethane foam board insulation offers high level of compression and strength. Metal or plaster board bonding can further enhance the quality of polyurethane foam board. A polyurethane foam board with metal or plastic board bonding can be used in applications that face extreme temperature conditions, -200 to 100^oCelsius. Its R-value of 7 to 8 per inch, also faces gradual decrease due to thermal drift. Using metal foil facings or reflective foil; the R value can be sustained for a longer period of time, allowing maximum retention of heat.

Installing Foam Board Insulation
It is always advisable to appoint a professional for the rigid foam board installation. However, if you want to work on the installation by yourself, then seek for the manufacturer's advice. Also go for a thorough check of local building fire codes. Here are few considerations that you need to keep in mind with respect to your installation.

• Protect the installation from direct sunlight. The sun's UV (ultraviolet) rays are a potential threat to the installation. The roofs that have been insulated, can be coated with tar, rubberized paint, plastic or rubber membrane.
• In warmer and colder climates, in order to prevent moisture related issues in the installation, vapor diffusion retarder should be utilized.Infestation by insects can also turn out to be major problem. They can reside under the foam boards by tunneling through them and making burrows, which ultimately reduce the R-value of the installation. So, an insect infestation test is also required before starting off with the installation procedure.
• Although foam board insulations do not easily catch fire, but if they are able to, then the fire can spread in an alarming rate, emitting highly toxic gases. So, a thick fire covering like a gypsum wallboard can be used as an efficient fire barrier for fire safety.

Rigid foam board insulation, although a bit costlier than other types of insulation is ideal for places which lack in space. Its high R-value makes it more efficient for home improvement, than its other counterparts, which have the same thickness. The foam board installation is an easy task, as time is not lost in installing the foam board with staples, instead glue or nails are enough to complete the work faster.