After you place a window into a window frame, you seal the window to the frame to set it into place and create an airtight enclosure. Both caulk and window putty successfully bond to the window and window fixture. You can use caulk, but the correct application will seal the window properly, last longer and improve the window’s appearance.
The U.S. Department of Energy puts window sealant products in the same category with caulk. Manufacturers often refer to window putty as window glaze. Caulks are formulated differently to seal and bond a variety of surfaces and textures properly. Window sealant is specifically formulated for windows.
The general differences in caulks, including window putty, are their ingredients. Each type of caulk expands or shrinks. The quality of caulk also varies greatly. The higher the quality of caulk, the more expensive it will be.
Window putty generally comes in one of three formulations: water-based foam sealant, butyl rubber or latex. Each of these sealants’ durability and cure time varies. Water-based foam sealant expands, while butyl rubber and latex shrink. Water-based window sealants generally take longer to cure. Latex sealants require painting over it on exterior surfaces to properly bond, while butyl rubber doesn’t adhere well to painted surfaces.
Based on factors related to the type and quality of caulks and window putties, consider the type of window you are sealing and the additional work involved. Additional costs include potentially repainting the windows and caulking the windows again within a year or two. If the seal breaks or wears down, the windows will become drafty and increase the heating bill. If caulking a window to quickly repair and seal leaks -- such as sealing the window during cold weather -- consider purchasing a sealant most applicable for the windows when the weather becomes warmer. The investment for a higher quality caulk pays off in the long run.
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