Window Fins Vs. Finless Windows
5 years, 11 months ago Posted in: Windows 0

What is a window fin?

A fin is a vinyl strip that extends over the edge of the outer window sash ans has pre-drilled holes.  The fin is a component found on new construction windows. The fin exentends on all sides of the window,  and is apart of the window assembly.

Where can you find the window fin?

The window fin is found outside of the window frame. See photo below.

Window Fin

The window fin is the vinyl strip around the exterior of the window that has pre-drilled holes for installation.












The fin’s pre-drilled holes help the installer position the window properly and securely, giving the window a tight seal protecting the home from water and wind infeltration.  During the window installation, the installer attaches the window with galvanized nails through the fins pre-drilled holes, to the 2 by 4 studs that frame the exterior of the home.


No Window Fins

All windows come with fins, some contracters alter the window to save them time on the installation. If a contracter alters the window fin, the warranty may be voided because the of the common product alteration clause found in most window contracts.

Windows without fins are called finless windows. Finless windows used for replacement windows by most contractors because it is cheaper and quicker to install. Some problems can arrise by taking this short cut.  Damage can occur to the frame of the window, since finless window installations do not allow proper window expansion and contraction.

Finless windows are attached to the side jambs of the home after the old window is removed. Finless installtion is only recommended for brick, stucco or wood pocket windows.  For all other home types AMMA certification states that replacement windows must be a fin install.

High Performance Homes follows AMMA certification protocol and installs windows with fins on all homes other than brick, stucco or wood pocket installtions.


Windows with and without fins come in a variety of energy efficient choices, such as double and triple-pane glass to increase thermal efficiency and decrease heat loss/gain through out the seasons. If you live in a cooler climate you should explore options to upgrade to a multiple pane glass.

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