Rigid Foam Insulation
The foam insulations are good substitute to the insulators like fiberglass or cellulose. The foam insulators are used where the high R-values are desired. Even though the cost is greater than that of the batt insulations or fiberglass rigid foam insulations are preferred for high performance. The R-value (per inch of thickness) of foam insulations range from R-4 to R-8. This range of R-values is 2-3 times greater than the r-values of other materials.
The foam insulations are made up of three materials which includes the extruded expanded polystyrene (XEPS), molded expanded polystyrene (MEPS), and polyurethane, polyisocyanurate or related chemical mixtures. Some of these are installed as liquids and other are panels made in the factory.
The molded expanded polystyrene is basically a closed cell material and can be molded into various items. This material is called as ‘beadboard ‘and its R-value is 4 per inch of thickness. A beadboard is made using expanded polystyrene beads which contain pentane. This is then mixed with some blowing agent and then poured into a container. Heating expand the beads many times. The beads are then injected into a mold and shaped as required.
The closed cell insulation forms the extruded expanded polystyrene and is similar to the MEPS. The polystyrene capsules are liquidated and a blowing agent is injected to form gas bubbles. Then the foaming liquid is forced into a shaping die. After cooling the panel is cut according to the requirement. Both the MEPS and XEPS are useful for structural insulating panels and insulating the concrete forms.
Polyurethane and polyisocyanurate are again closed cell foams that are filled with a low conductivity gas in the cell. The R-values of these materials are between R-7 to R-8 due which it gives high thermal resistance.
Since the air is the most effective all insulators use the air to minimize the insulators conductivity to prevent the heat loss. The sheer volume of compressed air in rigid foam insulation gives it better thermal performance. The penetration of moisture causes permanent loss in the R-value which is one of the causes of uselessness of the insulation over the time. But the rigid foam insulation material is ‘hydrophobic’ and hence cannot be penetrated by the moisture. The rigid foams work in a way to slow down the flow of the heat through building. It also seals the building by preventing from the air leakages and outside drafts. This insulation helps you to save money by the reducing the loads on the energy used for heating and cooling the building. This insulation provides you a comfortable living and working place.
There are certain problems that need to be taken care of if you install the rigid foam insulation. The foam boards are prone to the potential insects tunneling. This reduces the R-value of the boards. It is also hazardous to the potential integrity of the total insulation. For this reason make sure that the boards are treated with insecticides like a borate compound. For a below grade wall it is better to install the boards on interiors instead of installing on the exteriors. Though the insulation does not readily catch fire a fire barrier is advisable.