Concrete Block Insulation
A wall’s thermal resistance, or its R-value, is its ability to slow the transfer of heat from one side to the other. Concrete block makes a cost-effective and structurally sound wall, but it has little thermal resistance. Depending on the density of the blocks, an 8-inch thick block wall without any other type of insulation has a thermal resistance value between R-1.9 and R-2.5.
Types of concrete block insulation
There are several ways to incorporate foam insulation – such as polystyrene, polyisocyanurate or polyiso, and polyurethane – into concrete blocks. The hollow cores of concrete blocks can be filled by pouring and/or injecting loose foam beads or liquid foam.
Polystyrene concrete is a relatively new building material that has broad applications and solves many problems of traditional concrete blocks. It is made from a combination of different materials to create a product that is durable, lightweight and offers lots of architectural design potential. Different manufacturers have different combinations of materials, polystyrene concrete is generally made from a mix of cement silica aggregate, recycled polystyrene granules and modifying agents such as setting accelerators. The end result is a product that offers both construction and insulation properties.
A polystyrene block can be used solely as an insulation system for new or existing buildings, or it can be used as a construction material in a variety of ways. Because the bricks are lightweight they reduce the labor required for construction of masonry walls, and at the same time, increase the speed of construction.
Polyisocyanurate, also called polyiso, a thermosetting type of plastic, is a closed-cell foam that contains a low-conductivity gas (usually hydrochlorofluorocarbons or HCFC) in its cells. The high thermal resistance of the gas gives polyisocyanurate insulation materials an R-value typically around R-7 to R-8 per inch.
Polyisocyanurate insulation is available as a liquid, sprayed foam, and rigid foam board. It can also be made into laminated insulation panels with a variety of facings. Foamed-in-place applications of polyisocyanurate insulation are usually cheaper than installing foam boards. They also usually perform better since the liquid foam molds itself to all of the surfaces.
Polyurethane is a closed-cell foam insulation material that contains a low-conductivity gas (usually hydrochlorofluorocarbons or HCFC) in its cells. The high thermal resistance of the gas gives polyurethane insulation materials an R-value typically around R-7 to R-8 per inch.
Polyurethane insulation is available as follows:
- Sprayed-foam polyurethane insulation
Sprayed or foamed-in-place applications of polyurethane insulation are usually cheaper than installing foam boards. These applications also usually perform better since the liquid foam molds itself to all of the surfaces.
- Rigid polyurethane foam board insulation
Foil and plastic facings on rigid, polyurethane foam panels can help stabilize the R-value, preventing thermal drift. Testing suggests that the stabilized R-value of rigid foam with metal foil facings remains unchanged after 10 years. Reflective foil, if installed correctly, can also act as a radiant barrier, which adds another R-2 to the overall thermal resistance. Panels with foil facings have stabilized R-values of R-7.1 to R-8.7 per inch.