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December, 2004

Low Pressure One-Component Foam for Windows and Doors

One-component polyurethane foams (OCF) have been traditionally used for many years to successfully seal around windows, doors and skylights, in addition to a variety of other areas, such as along base plates, corner joints, around plumbing and utility penetrations, etc. As the use of alternative materials for manufacturing windows has become more common, in particular, vinyl windows, the potential for window failure or defects due to improper installation has also increased. One reason is that the materials used to make the windows have become increasingly lighter and less structurally robust, and therefore more prone to distortion.

Consequently, the proper use of one-component foam to seal the rough opening gap has become more critical, so that the pressure exerted by the expanding foam does not distort the window frame such that the window fails to open and close easily. Knowledgeable installers are still able to properly apply most OCF products around any type of window simply by being more cautious not to overfill the cavity, and allowing for the necessary expansion of the foam prior to finishing the window installation. However, some window manufacturers have expressly voided any warranty for some of their products if it is found that foam was used during the installation process, regardless of whether the claimed defect is related to the use of the foam, in the first place (the reasoning being that if the foam was improperly applied, then it is more likely that other aspects of the installation may have also been done improperly, as well).

This trend has led to the development of low pressure one-component foam sealants that are specifically formulated for use around windows and doors, so that the window will not bow or distort from the pressure of the expanding foam. In addition, the industry is developing test standards and guidelines, such as the American Architectural Manufacturers Association (AAMA) Test Standard 812-04 "Voluntary Practice for Assessment of Single Component Aerosol Expanding Polyurethane Foams for Sealing Rough Openings of Fenestration Installations", to specifically quantify the pressure that is exerted by expanding one-component foam. It is recognized and accepted that it is not, necessarily, the expansion of the foam that can lead to a distorted frame, but the pressure that is exerted during the curing and expansion which is the most important property to control in order to avoid an improper installation (in fact, expansion is desired, as it helps the applied foam fill in the uneven surfaces and crevices of the rough opening gap).

Handi-Seal Window and Door Sealant was the first one-component low pressure foam sealant designed specifically for this application. The patented formula of Handi-Seal provides a sealing foam with one of the lowest pressure build properties available, and is fully compliant with AAMA 812-04. In addition, the predominantly closed-cell structure of Handi-Seal provides improved water resistance, compared to other, more flexible open-celled foams which can absorb or wick water, thus leading to increased chances for wood rot or mold formation.

Handi-Seal Window and Door Sealant is available as a "straw foam", as well as a "gun foam" that is dispensed through one of the professional one-component foam dispensing units available from Fomo Products, Inc. Handi-Seal is colored grey, for easy visual identification after application.

This information is provided as a service, and is not necessarily meant to reflect any recommendation, guideline or position of Fomo Products, Inc. Each individual user must determine product suitability for any particular purpose.


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