Double hung, single hung, and sliding windows and doors all utilize window weatherstrips that slide or sweeps between the sash and the frame. Such weatherstripping must be tolerant of shearing movement while still maintaining a seal. Fuzzy piles, sometimes accompanied by a plastic or Mylar fin, are frequently used for this purpose at the perimeter of the sash, or along the frame where the sash meets the frame.
Image above left: Sweep-type weatherstripping with Mylar fin arrow embedded in the pile for better control of air infiltration. The original trade name, fin-seal, has now been popularized to represent all such products. Right: Sweep weatherstrip without fin. The rigid backer threads into receiving slots that run along the sash or frame. In the sectional detail through the top also called the head of an aluminum thermally broken double hung window, the master frame has been coded yellow.
The sash is blue. The two thermal breaks are gray. The two window weatherstrips are colored orange and circled. The weatherstrip on the left is threaded into the sash and weathers rubs and seals against against the master frame.
The weatherstrip on the right is threaded into the master frame and weathers against the sash. All other operable window types utilize compression weatherstripping, such as bulbs or fins. These tend to seal better that sweep-type window weatherstrips because they are actually compressed between sash and frame when the sash is locked in the closed position.
Compression weatherstrips can also be called gaskets. Performance differences between products of sweep vs. Image above, at left: Bulb weatherstrip with a rigid backer for threading into a slot which has been extruded into an aluminum or PVC sash or frame. These window weatherstrips are extruded from vinyl, TPEs thermoplastic elastomers , PVC, silicon, polypropylene and jacketed foams. There are literally thousands of window weatherstrips available on the market, varying by material, size, thickness, and backer configuration.
If replacement window weatherstrips are needed, the best way to achieve success is to obtain a sample of the material, measure it using a caliper-type micrometer, detail it and send it to various suppliers, even accompanied by photos of the material. If any suppliers claim to have a matching product, request a sample and compare it with your original. Architects and engineers, take this course for PDH credit here. Window weatherstrips and gaskets are designed to be compressed when in service.
The window manufacturer will select a particular weatherstrip type for the product, and will decide, possibly in coordination with the weatherstrip manufacturer, to what extent the weatherstrip should be compressed.
This decision must be made judiciously. If the window weatherstrip is compressed too hard, meaning it is too thick for the space in which it resides, the window will be difficult to operate. If weatherstripping is too loose, excessive air infiltration or even water penetration could result.
As windows are operated year after year, many weatherstrips will remain compressed even while not under compression. Other products may erode over time, loosening the seal. Therefore the choice of weatherstripping material and its initial compression has large ramifications for the functionality of the window product not only when it is new, but also for many years in the future.
Here we will discuss the frame of the window. Glass, the thing that makes a window a window, will be discussed later. These calculations explain. If you buy cut lengths, remember to account for the cut length tolerances in the RMA Handbook. Once you calculate the costs of labor and material waste , cutting your own gaskets by hand might not seem so cost-effective.
When you install a locking gasket, push the ends together and leave the extra material in the loop that forms. Then press down the loop so that you force more material into the gap. This keeps the gasket from becoming over-stretched. Next, spray the locking gasket with a silicone-based lubricant or soap and water.
Install the glass on the body size first, resting the bottom of the glass in the locking gasket. Finally, use a hand tool to the lock the gasket back into itself. Do you need help with window gasket design or installation?
Elasto Proxy distributes window gasket materials and supplies cut lengths using our water jet cutting equipment. To request a quote or for more information, contact us.
Save my name, email, and website in this browser for the next time I comment. Commodity rubber is used for sealing and insulation in many consumer, commercial, and industrial applications.
Examples include the door seals and window seals on heavy. Types of Window Gaskets Depending on the window gasket application, engineers can choose foam profiles, D-shapes, C-channels, U-channels, or various types of glazing seals.
Window Gasket Materials To avoid gasket failure , always consider the environment when selecting rubber materials. Window Glass Thickness Measure the thickness of the window glass so that you can determine the size of the edge that your window gasket needs to grasp and hold.
Because of the age of some windows, replacement gaskets may no longer be available. Where gasket replacement is not feasible, an alternative option is to cut out the top of the existing gasket bulb and apply elastomeric sealant.
Although less expensive in the short term, this repair method creates an ongoing maintenance issue, due to the relatively short life expectancy of sealants. During installation, correct placement of sealant is important, both to ensure adhesion and to avoid blocking voids in the frame that allow moisture to exit the assembly.
Air and water infiltration through windows may also be the result of aging frames, which have developed cracks at welds and stress points. If deterioration is limited, such that the window is still structurally sound, it may be possible to retrofit the existing assembly, rather than replace it. To protect against leaks and drafts, an additional layer of glass — a "storm" pane — may be added at the building interior. However, such installations tend to render formerly operable windows inoperable and may result in condensation problems if not carefully designed and installed.
Interior storm windows are therefore usually considered temporary measures. Another possible cause of leaks may be a poor seal between the operable and fixed portions of the frame. Depending upon the age and size of the windows, and the degree of deflection, these seal defects may or may not be repairable. As with gaskets, replacement parts for older windows may no longer be available. Condensation is another sign of trouble with windows. Fogged glass is often caused by a breach in the seal of insulating glazing units.
These double- or triple-glazed windows incorporate multiple glass panes separated by an air- or inert-gas-filled space. When seals in insulating glazing units fail, moisture can become trapped between panes. Depending upon the extent of the problem, it may be possible to replace the glass, while keeping the existing frame. However, if the window is also exhibiting other problems, it may be worth considering complete replacement.
To identify the source of condensation at the interior surface of windows, an investigation should consider when the problem occurs, and where.
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