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Pella® Impervia® Fiberglass Casement Window


When it comes to performance, Pella Impervia fiberglass casement windows are an overachiever. Made from our incredibly strong, proprietary fiberglass material, casement windows are hinged on one side and vent open on the other. A revolutionary Easy-Slide Operator hardware allows you to open and close your windows with one simple motion. And with a durable powder-coat finish, Pella Impervia casement windows deliver a timeless, long-lasting look.

Impervia Casement Window Features

Why Fiberglass?

  • Superior strength with our proprietary fiberglass material61
  • Rot- and corrosion-free
  • Tested for the extremes and suitable for all climates
  • Heavy-duty powder-coat finish, including Black


  • Innovative Easy-Slide Operator hardware, winner of the 2021 IBS Best in Show Award, is available
  • Solid- and dual-color frames in an up-to-date color palette
  • Matching fixed and operable styles available for larger window combinations
  • Durable three-way corner joints for added strength, durability and reliable water performance

Pella Impervia

Get windows ready to handle virtually anything life throws at them. Pella Impervia products are made from our proprietary fiberglass, the strongest material for windows.61

Pella’s exclusive fiberglass will never rot or corrode and resists dents, bends and breaks — and the list goes on. With a tough-as-nails powder-coat finish, your windows will never need to be painted or refinished.

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Inside Pella Fiberglass

Pella Impervia windows are created from our exclusive fiberglass formula. A structural mat places rovings in a specific, intricate order to meet our high strength standards. Additional layers of strategically placed rovings are added, then the materials are pulled through a machine, injected with polymer resin and heated. It creates an entirely new, thermoset material which won't break down when exposed to the elements or lose its shape in extreme heat — unlike other materials.

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cutaway of impervia products

The Pella Difference

We do more than just create windows and doors. We test beyond industry requirements and innovate continuously to make beautifully designed products that you can be proud to own.

For the Pros

Pella Impervia Casement Window Specs & Install Details

  • Unmatched strength and lasting durability for proven performance and sleek style
  • Tested and designed for the extremes
  • Operable casement windows available in sizes up to 37-1/2” x 79-1/2”
  • Fixed casement windows available in sizes up to 71-1/2” x 79-1/2”
  • Performance class and grade LC40-LC50
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Product Downloads

Awards and Certifications

Options for Pella Impervia Casement Windows

Choosing Your Window


Make a design statement with window combinations. Additional combinations are available. See your Pella sales representative for the complete offering.

For Pros

Combination Design Considerations
  • Made just for your remodel or new construction project, unique and large factory-mulled assemblies help save time on the jobsite.
  • Integral mullion, tight mullion, 1/2” structural mullion or 1” structural mullion with additional steel reinforcements.
  • Residential and light commercial solutions designed and tested to ASTM E330 for structural test pressures up to 75PSF (DP50).
  • Meet or exceed structural framing requirements of the International Building Code section 2403.3 for more demanding commercial casement and awning window applications.
  • Ability to choose a solution based on project classification, including structural framing requirements for casement or awning specified projects.

Interior Finishes

Pella Impervia fiberglass products have a long-lasting factory powder-coat finish in your choice of three colors. Learn more about interior finishes.


For Pros

  • Pella Impervia products are made from our proprietary fiberglass material, the strongest material for windows, engineered for lasting durability.61
  • Our long-lasting powder-coat finish meets AAMA 624, which is a highly-rated fiberglass coating.
  • Exclusive thermoset material won't expand, warp or sag in summer heat, or shrink and turn brittle in harsh winter conditions.
  • Secondary Secure Vent Lock for extra protection.

Styling Your Window


The Easy-Slide Operator is a revolutionary way to operate your casement and awning windows. Simply slide to open and close, without the effort of cranking. Or select the fold-away crank, that folds neatly away, against the window frame. Both solutions allow roomside window treatments to hang neatly in your room.


Grille Patterns

Grilles give the appearance of individual window panes. Pella offers many grille patterns to help enhance your home's architectural style.


Grille Profiles

Grilles-between-the-glass create the classic look of individual windowpanes. Learn more about grille profiles.

3/4" Grilles-Between-the-Glass

Window Enhancements


Flat Screens

Conventional fiberglass screens come standard.

Pella InView™ screens let in 14% more light and are 8% more open for improved airflow compared to conventional fiberglass screens.5

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Pella products are backed by some of the strongest warranties in the business.

Learn more about Pella warranties