Insulation Factor for Foam

Foam Insulation

• Foam insulation comes as either boards that are attached to framing structures or as a blown-in or loose-fill type of insulation. Blown-in or loose-fill insulation comes in a liquid that, via specialized machinery, is sprayed either into building cavities, such as between walls during the construction phase, or directly onto surfaces in the completed building, typically the attic floor and ceiling, where the foam expands in place and sets in seconds. Both the board and spray-in types of foam insulation create a barrier that prevents the escape of heat from inside the home.

Insulation Factor of Foam

• The insulation factor of a material is given as an R-value. This is the unit of thermal resistance. The higher the resulting number, the better the material at insulating. Polyurethane foam is the most widely used foam insulation and has the highest R-value at around 6 to 6.5. However, one composite element of polyurethane foam is refrigerant gas, and as this naturally escapes over time – a process called thermal drift – the insulation factor of this material will decline as your home ages. Phenolic foam has an R-value of 4.8, while Isocyanurate plastic foam averages 4.3. Sometimes foam sprayed inside cavity walls is used in combination with glass fibre boards, raising the R-value by around 3.0. Foam boards can be covered by foil or plastic facings that not only prevent thermal drift, but that also add an extra R-value of approximately 2.0.

Point of Comparison

• Some of the other commonly used materials for insulation have significantly lower R-values. Fiber glass, the most frequently utilized insulation material, either in a blown-in loose-fill form or as batts – sheets or blankets of material – has an R-value of 3.2. This is the same as the R-value for cellulose, typically made of reconstituted recycled paper. Mineral wool, another material that is normally used in batts has an R-value of 3.1.

Other Benefits

• Aside from its higher R-value compared to other insulation materials – which, in the long term, will save the householder money on his energy bills – foam insulation has other advantages. Chief among these is its effective resistance to moisture. This not only prevents the foam itself from developing mold and mildew, but it also prevents excessive moisture from entering the home and causing such growth in the living areas. Because foam hardens to the contours of the building’s structure, it can help reinforce the integrity of structural components, such as rafters.