Understanding Closed Cell Foam Insulation Versus Open Cell Foam Insulation
Polyurethane spray foam is often categorized as either "open-cell" or "closed-cell". There are several major differences between the two types, leading to advantages and disadvantages for both, depending on the desired application requirements. In addition, polyurethane spray foam is an extremely versatile material that is available in a variety of final physical properties and densities, making it necessary for the end-user to have an understanding of these differences in order to choose the spray foam system that is best suited for the particular application requirements.
EnviroGreen's closed cell spray foam is among the most efficient insulating materials residentially and commercially available, with an R-value of 6.8 per inch. Common foam density for closed-cell polyurethane foam is approximately 1.7 to 2.0 pounds per cubic feet. This foam expands 20 to 30 times its initial liquid size, and rarely requires trimming which provides little to no waste. EnviroGreen's closed-cell polyurethane foams are usually characterized by their rigidity and strength, in addition to the superior R-Value. These heavier and denser foams have what is known as a closed-cell structure, which means that the gas (EPA approved Honeywell 245fa) bubbles that form during the application process remain permanently locked into the cured foam. These millions of microscopic bubbles created during the manufacturing stage remain closed and intact, thus trapping the reaction gases. Therefore the R-Value of EnviroGreen's closed cell foam is close to that of the reaction gas, or 6.8 per inch. Since there are no open interconnections between individual bubbles, the foam can not absorb water and also effectively diffuses (retards) the passage of water vapor. According to most building codes, a vapor retarder must have a perm rating of less than 1.0; EnviroGreen's closed cell foam meet this standard. And, very importantly, due to the closed cell structure and higher density range, it provides the optimum strength increasing shear and racking strength by up to 300%. EnviroGreen's closed cell foam, unlike open cell, stops convection (air-flow) both through and within the wall cavity. One additional note concerning closed cell foam is that some companies market and install closed cell foams without this 245fa (or comparable inert gas) blowing agent. These products, by definition, are no longer true closed cell polyurethane foams. Without this blowing agent the foam loses a significant amount of vapor diffusion and/or vapor barrier qualities and should therefore create concern when being used for these reasons, such as under floors or in the exterior walls of old wood-sided homes without code approved vapor retarders for example.
Open Cell Spray Foam
Spraying cathedral ceiling cavities with open cell foam to a 3 inch average
EnviroGreen open cell spray foam is also referred to as ½ pound or low density foam. This foam expands to over 100 times its initial liquid size, and may require trimming and disposal of the excess waste material after application. The physical characteristics of EnviroGreen's open-cell polyurethane foam usually include a softer, "spongier" appearance, as well as lower strength and rigidity than closed-cell foams.
Open cell foam cures soft while the irregular bubbles which form during the expansion-reaction process remain open and interconnected. EnviroGreen open cell foam derives its R value of 3.8 per inch from the dormant air within the open bubble pockets which is about half that of closed-cell foam. The R-Value of open cell foam is quoted close to that of conventional fiberglass and cellulose insulation because they all use the same principle of trapping dormant air.
However, these similarly quoted insulation values are very misleading since open cell foam greatly reduces air-flow and significantly slows moisture transfer relative to these competing conventional insulations. Please refer to the "R Fairy Tale" for more information about the inaccuracies of R-values. Open cell foam does not stop, but rather, significantly slows down convection through and within the wall cavity. Open cell spray foam is more permeable to moisture vapor, with perm ratings of approximately 16 per 3 inches thickness, therefore is not a code approved vapor barrier. Open cell foam should not be used in exterior applications, such as underneath a raised house, due to its inability to retard moisture flow. However, EnviroGreen open cell foams are incredibly effective as a sound barrier, having about twice the sound resistance in normal frequency ranges as closed-cell foam.
Applications that typically use open-celled foam include residential construction insulation, under roof trusses for "conditioned attics", and for sound deadening in media rooms, etc. Closed-cell foam, while a superior insulating product used in residential construction, is also used in a variety of commercial and industrial applications because of the excellent strength and insulating properties and vapor barrier qualities which may be required by building codes.
Hybrid 1.0lb to 1.2lb Open Cell Spray Foam
EnviroGreen also offers a spray polyurethane foam that includes characteristics of both closed cell and open cell products. Originally formulated and developed by Louisiana local Apex Foam Industries this insulation is referred to as a “hybrid” or “double density” polyurethane foam. This unique insulating product is by definition an open cell foam since it does not contain a blowing agent such as Honeywell 245fa which is required to be defined as a true closed cell foam. This insulation is characterized by its very rigid feel and additional strength relative to typical ½ pound open cell products, although it does not provide as much rigidity and strength as closed cell foam. The R-value is 5 per inch due to the additional “insulating material” instilled during the manufacturing process. Whereas open cell contains a half pound of insulating material per cubic foot and closed cell contains 1.8lbs per cubic foot EnviroGreen's hybrid foam contains 1.2 pounds of insulating material per cubic foot. This 1.2lb open cell foam exhibits similarly excellent air-barrier characteristics of closed cell insulation but less ability to retard the flow of moisture. Although EnviroGreen strongly encourages the use of only 245fa closed cell foam for exterior application such as under the framed floor of a raised house this 1.2lb product may be installed under certain circumstances.
Beware!!! Many foam companies install 1.2lb foam in place of a closed cell insulation that may have been quoted in an estimate or contract. It may be very difficult to detect the differences between these two products after installation. It has been our observation that there have been many cases where companies quoted closed cell foam but fraudulently installed 1.2lb instead without the knowledge of the homeowner.
141 Robert E. Lee Blvd., #227 New Orleans, LA 70124 Phone: 504-344-6762 Fax: 888-893-7259
