The Glass May Look the Same. The Installation Can Be Completely Different.
Two common frame configurations are:
- Nail fin
- Block frame
Pella distinguishes these as different window-installation systems.
What Is a Nail-Fin Window?
A flange extends around the exterior window frame.
That flange is attached to the wall framing or sheathing and integrated with the wall’s water-resistive barrier and flashing.
What Is a Block Frame?
A block or box frame does not rely on an exterior nailing fin in the same way.
It may be secured through:
- Frame screws
- Clips
- Other approved methods
depending on the opening.
Why Does This Matter for Replacement?
The correct frame depends on:
- Existing wall
- Siding
- Masonry
- Whether old trim is removed
- Replacement approach
One Is Not Automatically Better
The best system is the one designed for the actual wall assembly and project.
Window Performance Starts With Choosing an Installation Method That Fits the Opening.
Envirotech Exteriors can evaluate the existing wall and determine which replacement-window installation approach makes sense.