Seal The Deal
The Importance of Choosing an Effective Weatherstrip Product
by John St.John

A relatively minor component of any operable window or door unit plays a major role in the performance of that product. Weatherstripping is this integral part that facilitates performance of windows and doors in areas like sound transmittance, air infiltration, water resistance, thermal performance, operating force and aesthetics. As the  importance of these elements grow, so does the need for manufacturers to find the proper seals that will satisfy their specifications best.

Weatherstrip Insertion

In recent years, one major focus in the fenestration community has been the rush to reduce and/or shift the labor burden for insertion of the weatherstripping. Most manufacturers have incorporated specialty-processing equipment on their lines and likely have some type of pre-insertion of seals done by suppliers or third parties. This is especially prominent with the high-volume PVC window manufacturers. Innovations in equipment allow for multiple weatherstripping locations to be filled during the extrusion process. In addition to the inline systems, several other types of equipment have evolved to assist with insertion and application of the weatherstrip on the manufacturing floor. Continuous improvement is always a concern in manufacturing and much collaboration between the suppliers and their respective customers has generated unique solutions to streamline the application processes.

Labor is also reduced when weatherstrip is fabricated by the vendor or third-party company. When the sizes of windows and doors can be predicted with some certainty, seals can be processed so they arrive ready to install at the manufacturer’s lines. Many have found this type of service is worthwhile, as it will free up the production workers to concentrate on core processes.

In addition to efforts to reduce and shift labor, it is evident that a total supply concept is becoming the practice at most manufacturers for vendor partners. With rating systems gaining in popularity, as they have been successful with the major components such as wood, aluminum, glass, etc., other components such as weatherstrip are being transitioned into these systems. Gone are the days when price played the primary role in vendor selection. Metrics such as quality, service and supply are not selling points, but benchmarks that need to be met in order to be in the game. Fenestration companies are realizing that employing these standards across their vendor bases is the way of the future.

Different Weatherstrip Types

With a growing importance on achieving higher product ratings and a desire to reduce field service, manufacturers have showed their preference toward high-performance weatherseals. Foam weatherseals have grown in popularity recently as they can address these concerns readily. Once considered overkill and overpriced, the industry is realizing this material upgrade provides many short- and long-term benefits that exceed the initial cost differential.

Some new products on the market provide manufacturers a choice for weatherstrip application methods. Typically t-slots and pockets are pulled and pushed in respectively. There was only one product and a corresponding way to accomplish its insertion. Seals that can be applied in either manner afford assembly freedom without regard to the design of the weatherstrip. These products are ideal for existing window designs because they allow manufacturers to tailor the assembly process to meet their needs without having to design custom seals.

One of the latest innovations in weatherstrip has been the usage of non-pile products in sliding applications. The wood window manufacturers have been moving toward a tilt style of double-hung versus the traditional compression systems. These new systems now require weatherstripping on either the jambs or stiles to seal the unit. This situation is solved by either applying a traditional weatherseal or by utilizing a jambliner system that has co-extruded seals. The PPI Division of our company utilizes an Alcryn bulb on either, all or just the primary sealing locations. In accordance with the North American Fenestration Standard, the seals have t-slots extruded below them for field replacement. Co-extrusion of seals such as projected windows, have been around for a while in compression applications but their use in sliding applications is relatively new to the market. To complement the co-extruded systems, high-performance sliding seals have been in increased demand from the market. This has stimulated the research and development functions and subsequent new product offerings have arrived from the vendor companies. A variety of new wrapped and coated foam seals, as well as coated dual durometer bulbs are now being tested and used by the manufacturers. As these types of seals are being used, an interesting dilemma comes to light as certain performance metrics gain while others may become compromised. Usually a balance of operating, closing and installation force is combined with serviceability and cost in order to achieve the desired result.

As the sealing systems are being found to have a very important effect on overall performance, it is increasingly important for designers to consider the seals earlier in the process. Many of my customers have realized the benefits of this involvement and are utilizing our resources early and often. While designs are still on paper, the latest products and innovations can be incorporated with little difficulty. Experienced and detailed information that is often beneficial to manufacturer’s efforts can be exchanged at this level.

Improvements to the AAMA 701/702-2000 (Voluntary Specifications for Pile Weatherstripping and Replaceable Fenestration Weatherseals) are on the horizon and the new standard will offer detailed information on weatherseal attributes to date. The manufacturers have expressed their concerns that the data provided in the old standard does not address “real world conditions” as they affect the seals over the lifetime of the window. In response, the task group is testing seals in compressed states with hot/cold cycling, increased exposure to ultraviolet light and reporting new data such as compression load deflection, compression set and shrinkage. While traditional design considerations specific to the window and door system will remain the dominant method of seal choice, this new information will give designers detailed data to assist with determining what products will be suitable for use in achieving their overall performance objectives.

John St. John is the director of sales and marketing for the Foam-Tite division of the Amesbury Group. Foam-Tite manufactures extruded TPV foam weatherseals in Amesbury, Mass.