Rigid Foam Board Insulation

Rajib Singha Apr 20, 2019
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Starting from the roof till the base or the foundation, you can insulate every part of your house using rigid foam board insulation. Apart from being a perfect thermal insulator, it provides additional strength to the skeletal structure of your house too. Let's learn about this insulation.
Foam board insulation is better than other types because of its high R-value (resistance against heat flow). Different parts of buildingĀ are insulated using this. 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 with the help of 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 the insulation. More information on the same follows...

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 degree Celsius) 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. It provides excellent resistance to moisture, and consistency in density and it is 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 100oCelsius.
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.

The Advantages

  • One of the main advantages of using this type of insulation is making the insulated areas moisture-proof. The problem with other types of insulation is that they tend to absorb moisture thus, deteriorating the insulation factor, and probably hamper the shape of the insulation. These factors do not apply to rigid foam board.
  • For most types of insulation, insects and rodents could be a major issue. But with foam board, such pests do not find a favorable environment to live and thrive.
  • Installation of the foam board, is probably the easiest job and the least messy as compared to other forms of installation, which require protective equipment.

Installation Instructions

It is always advisable to appoint a professional for the installation. However, if you want to do the job 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. The roofs that have been insulated, can be coated with tar, rubberized paint, plastic or rubber membrane.
  • Although foam board insulation does not easily catch fire, but if they do, then the fire can spread at 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.
Insulation using rigid foam, although a bit costlier, is ideal for places which lack in space. Its high R-value makes it more efficient for home improvement than its other counterpartsĀ having same thickness. The installation is easy, as time is not lost in installing the foam board with staples. Instead glue or nails are enough to get the job done faster.