The Not So Green Issues With Polystyrene Insulation
The August 2009 edition of Environmental Building News has a lead article dealing with the major issues facing a very popular, versatile and widely used form of insulation. This is Polystyrene insulation, which is marketed in two major forms: Extruded and Expanded.
Extruded Polystyrene is commonly used in sheathing and for below grade foundation and sub-slab applications. It is commonly seen as four foot by eight foot rigid board slabs with a smooth finish in various thicknesses. It is often referred to as "pink or blue board." The Expanded form is used primary as an under layerment for Exterior Insulation and Finish Systems (EIFS), commonly seen today as a popular form of stucco siding for homes and other buildings.
One of the main advantages of polystyrene insulation is its ease of use, moisture resistance and relatively high R-value of about 5 per inch of thickness for the extruded form. (The expanded form, which has a pebble-like surface, has a slightly lower R-value.)
The main concern here is the fire retardant chemical known as hexabromacyclododecan (HBCD) which is required by law to be added to the material. While HBCD is present in amounts ranging up to 0.5% to 1.2% by weight, is being investigated as a health threat. Recent studies seem to indicate that it may effect the thyroid and liver. It is also classified as a Persistent Bioaccumulative, meaning that it does not break down fast, and remains in the environment for long periods of time, thus increasing its toxic effects.
In addition to he HBCD, polystyrene also has as its components benzene, ethyl benzene, toluene and styrene, all known to be either carcinogens or to have toxic effects.
The question has been raised as to whether to remove HBCD from polystyrene that is destined for below-grade installations. This would clean up one problem, but not the issue of the fact that when the product reaches its end of useful life, it is rarely if at all recycled properly. It IS possible to recycle polystyrene, but the HBCD would persist, and be incorporated into new products, furthering the spread of the HBCD threat.
Attempts to re-formulate polystyrene have not yet been successful. There are, however several good environmentally friendly alternatives to it. These can also be used as polystyrene as a sheathing as well, which has the superior effects of reducing thermal bridging, which occurs if fiberglass insulation is placed between wall studs without sheathing.
One very good alternative for above grade interior insulation is polyisocyanurate, often referred to as polyiso. This has an even higher R-value per inch, but must be protected from moisture. Thus, for above grade insulation, the best alternative is to switch to interior application of the insulation.
Another substitute would be polyurethane spray foam. In addition, I have covered the use of other forms of spray-foam insulation in previous blog entries, one of which is made from rapidly re-produced sources, such as the castor bean. These spray foams have the advantage of producing a better air barrier seal than rigid board insulation, as they fill the cavity. The R-value is about the same as that of fiberglass
Spray polyurethane has been studied for below grade use with good results as well, in both foundation and sub-slab use. Rigid rock wool has also been used, but the R-value is lower. However, when drainage and moisture issues are present, it is of value, as it is hydrophobic, meaning that it does not attract and hold water. A major drawback to its use is the fact that it is not widely available. The same is true for rigid fiberglass. Another possible substitute for below grade slab insulation could be Pittsburgh-Corning's FoamGlas. This is marketed in Europe, but not widely available in the U. S. It is also considerably more expensive than the materials that I have detailed above.
Regarding Structural Insulated Panels, (SIPS) which have grown rather popular in mass building, as they combine insulation as part of a total support exterior wall. These have a sandwich system that has Oriented Strand Board (OS
on each side, with polystyrene as a filler. Once again, it is possible to re-formulate this product with polyurethane. This actually has the advantage of producing a much stronger system than polystyrene, which is of value in hurricane-prone areas.
Insulated Concrete Forms also utilize polystyrene, and it is a bit more difficult at this time to find a substitute for this. Cement-wood fiber has been tried, but its R-value is less, but is possible to boost this with the application of mineral wool inserts.
In summary, we need to re-think whether we should be using polystyrene rigid board insulation for green and sustainable building.
Extruded Polystyrene is commonly used in sheathing and for below grade foundation and sub-slab applications. It is commonly seen as four foot by eight foot rigid board slabs with a smooth finish in various thicknesses. It is often referred to as "pink or blue board." The Expanded form is used primary as an under layerment for Exterior Insulation and Finish Systems (EIFS), commonly seen today as a popular form of stucco siding for homes and other buildings.
One of the main advantages of polystyrene insulation is its ease of use, moisture resistance and relatively high R-value of about 5 per inch of thickness for the extruded form. (The expanded form, which has a pebble-like surface, has a slightly lower R-value.)
The main concern here is the fire retardant chemical known as hexabromacyclododecan (HBCD) which is required by law to be added to the material. While HBCD is present in amounts ranging up to 0.5% to 1.2% by weight, is being investigated as a health threat. Recent studies seem to indicate that it may effect the thyroid and liver. It is also classified as a Persistent Bioaccumulative, meaning that it does not break down fast, and remains in the environment for long periods of time, thus increasing its toxic effects.
In addition to he HBCD, polystyrene also has as its components benzene, ethyl benzene, toluene and styrene, all known to be either carcinogens or to have toxic effects.
The question has been raised as to whether to remove HBCD from polystyrene that is destined for below-grade installations. This would clean up one problem, but not the issue of the fact that when the product reaches its end of useful life, it is rarely if at all recycled properly. It IS possible to recycle polystyrene, but the HBCD would persist, and be incorporated into new products, furthering the spread of the HBCD threat.
Attempts to re-formulate polystyrene have not yet been successful. There are, however several good environmentally friendly alternatives to it. These can also be used as polystyrene as a sheathing as well, which has the superior effects of reducing thermal bridging, which occurs if fiberglass insulation is placed between wall studs without sheathing.
One very good alternative for above grade interior insulation is polyisocyanurate, often referred to as polyiso. This has an even higher R-value per inch, but must be protected from moisture. Thus, for above grade insulation, the best alternative is to switch to interior application of the insulation.
Another substitute would be polyurethane spray foam. In addition, I have covered the use of other forms of spray-foam insulation in previous blog entries, one of which is made from rapidly re-produced sources, such as the castor bean. These spray foams have the advantage of producing a better air barrier seal than rigid board insulation, as they fill the cavity. The R-value is about the same as that of fiberglass
Spray polyurethane has been studied for below grade use with good results as well, in both foundation and sub-slab use. Rigid rock wool has also been used, but the R-value is lower. However, when drainage and moisture issues are present, it is of value, as it is hydrophobic, meaning that it does not attract and hold water. A major drawback to its use is the fact that it is not widely available. The same is true for rigid fiberglass. Another possible substitute for below grade slab insulation could be Pittsburgh-Corning's FoamGlas. This is marketed in Europe, but not widely available in the U. S. It is also considerably more expensive than the materials that I have detailed above.
Regarding Structural Insulated Panels, (SIPS) which have grown rather popular in mass building, as they combine insulation as part of a total support exterior wall. These have a sandwich system that has Oriented Strand Board (OS
on each side, with polystyrene as a filler. Once again, it is possible to re-formulate this product with polyurethane. This actually has the advantage of producing a much stronger system than polystyrene, which is of value in hurricane-prone areas.Insulated Concrete Forms also utilize polystyrene, and it is a bit more difficult at this time to find a substitute for this. Cement-wood fiber has been tried, but its R-value is less, but is possible to boost this with the application of mineral wool inserts.
In summary, we need to re-think whether we should be using polystyrene rigid board insulation for green and sustainable building.
Posted by Alan L. Englander at 8/23/2009 6:36 PM 
Categories: Rigid Boardstock Insulation, Below Grade Wall and Slab Insulation, Exterior Insulation and Finish, HBCD Fire Retardant, Expanded and Extruded Polystyrene, Structural Insulated Panels
Categories: Rigid Boardstock Insulation, Below Grade Wall and Slab Insulation, Exterior Insulation and Finish, HBCD Fire Retardant, Expanded and Extruded Polystyrene, Structural Insulated Panels
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