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  • Improve your home’s energy performance
  • Fix uninsulated & drafty windows
  • Fix nonfunctioning windows
  • Help reduce your power bills
  • Preserve your home’s vintage charm

All while maintaining the original windows and glass.

The Problem.

You love the look of your vintage windows, but they’re not aging gracefully. You’re torn because you could always get brand-new, energy-efficient window replacements, but you don’t want to lose the charm.

Owning an old home can sometimes be challenging. While you love the charm of your vintage home, it can be costly and time-consuming to manage.

Some of the challenges of owning an old home can include:

  • A loss of heat and air conditioning through leaky windows.
  • Water damage and leaks around window frames.
  • Difficulty installing and operating bulky storm windows.
  • Trouble reducing outside sound through single-pane windows.
  • A high cost to maintain vintage windows.
  • An impact on the original charm and value if you replace the windows.

Did you know that the average home can lose up to 30% of its heat or air conditioning energy through the windows? SLIPs are designed to maintain the beauty of your original windows while increasing the energy efficiency of your home. In fact, in terms of insulating power, SLIPs are similar to double-paned windows.

SLIPs will ensure your window sash remains fully operable, without the traditional storm window issues, which require opening two sets of windows.


To solve this problem, we created Slim Line Insulating Panes (SLIPs) to take your Single Pane and transform it into a Dual Pane! This allows you to update your windows’ efficiency while maintaining the character and original architecture of your home or building.




The Slim Line Insulating Pane is a sleek, low-profile addition to your single-pane window.

We have made it possible to add a TEMPERED pane directly to each sash overlaying your current glass setup. This essentially turns your single-pane window into a simulated double-paned window. The frame of the SLIP™ is an attractive, low-profile, pressed metal extrusion.

This simple solution can rejuvenate single-hung, double-hung, casements, and more. This modernization is a long-term solution that does not need to be reinstalled each season.

SLIPs are highly effective, well designed, and well priced, giving you superior value compared to alternatives. SLIPs have a sleek look and feel with a low profile that blends into the sash; you’ll hardly know they are there.

Another key aspect is that SLIPs will ensure your window sash remains fully operable, without the need to open two sets of windows or remove any components as you sometimes get with storm windows or inserts.

The Benefits.

Adding SLIP™ to the windows in an average household will result in a cost savings of 72.9% for windows.

Our goal is to improve upon this by updating each window’s efficiency while keeping the windows true to the look and feel of the building. So, how does the SLIP accomplish this?

  • Increased energy efficiency
  • Reduced sound
  • Less expensive than a window replacement
  • Maintains original window glass
  • Stays historically accurate and functional 
  • Solid, well-designed construction and material
  • Interior or exterior install
  • Options of clear, obscure, or Low-E
  • Tested and proven product (Click to check out large projects.)
  • Low future maintenance costs

Learn how the window upgrade products can increase comfort, save money, and provide a positive return on investment.

Need more reasons to choose Window SLIP?

Before - Single Pane Window

Single-Pane Window

Without SLIP
Increases bills due to high energy loss

After - Single Pane Window

Single-Pane Window

Reduces bills by up to 72%!


Work with an installer or contractor of your choice to collect window measurements. Once you submit your measurements, we’ll assemble and ship your custom contractor SLIPTM Kits. These kits include all of the custom-sized materials your contractor or installer will need for a successful installation.



DO I INSTALL THIS PRODUCT MYSELF? If you have exceptional carpentry or handyman skills, you may be able to install SLIPs yourself. For most installations, it’s best to work with a contractor or window installer in your area to ensure the best possible outcome. We’ve prepared a step-by-step installation video that you can share with your contractor.

HOW DO I GET STARTED? Every kit we create is customized to the measurements you provide, so start by watching our guide on how to measure your windows. Then, work with your contractor to collect the measurements for your windows and submit them to us when you request a quote.

WHAT IF I NEED ASSISTANCE? You can always reach out to our team at sales@windowslip.com or fill out our contact form, and we’ll be happy to answer any of your questions.


What do they cost?

Tempered clear SLIPs cost around:


*Dependent of glass type and OA dimensions
*The square foot of the SLIP is only the area of the existing glass, not the entire window.


Casement SLIP™


Double-hung SLIP™


Here are the top 10 reasons to upgrade your single-pane windows with a Window SLIP™.

The true mortise and tenon construction of antique windows is incredibly strong, and even when it begins to weaken, it is easily repaired. Many unique window shapes were created because of the craftsmanship of wood joinery. Antique windows were built to last and not end up in a landfill.

Antique wood windows are constructed of old-growth timber. The wood is much denser and more weather-resistant than today’s tree-farmed softwoods. Delicate profiles are possible because of the wood’s density. These windows are still around, even with years of neglect, because the wood is very high quality, requiring no cladding or additional materials to give them weather resistance. Minus all the ugly paint, wood windows are usually quite beautiful, graceful, and strong.

Even the glass in antique windows tells a story. It may be roundel or cylinder glass, each indicating a certain manufacturing era. Old glass has various colors and textures that are a delight to the eye. Two layers of glass are better than one, and in an antique home, the second layer of glass should be the storm window that protects the original.

Polyvinyl chloride (PVC) is becoming one of the greatest concerns in the building industry. Not only does its production create an environmental nightmare, but the gasses it emits over time are also becoming a concern. Heaven forbid your house catches fire, as burning PVC can release toxic amounts of dioxin. If you are concerned about lead, please understand that it is used as a stabilizer in PVC manufacturing. If you are concerned about our planet’s health, you should read up on efforts to reduce the use of vinyl.

Replacement windows are set into the window opening, and the sash is smaller than the originals. You get less viewing area and less light. Who wants less light?

According to the Field Study of Energy Impacts of Window Rehab Choices conducted by the Vermont Energy Investment Corporation, the University of Vermont School of Civil and Environmental Engineering, and the U.S. Army Cold Regions Research and Engineering Laboratory, the estimated first-year energy savings between a restored wooden window with a good storm window vs. a replacement window was $0.60. Yup, less than a buck. In their conclusions section, they noted, “The decision to renovate or replace a window should not be based solely on energy considerations, as the difference in estimate first year savings between the upgrade options are small.” Broken glass, failed glazing, no weatherstripping – these minor and repairable items are what really affect energy efficiency in windows.

Replacement windows are touted as a way to save energy, but when evaluated from the perspective of the entire production, the shipping, installation, and removal process when replacing windows consumes a whole lot of energy. Viewed the other way, an older building has a great deal of embodied energy. If the total energy expenditure to manufacture replacement windows is considered, the break-even period stretches to 40-60 years. In the words of Richard Moe, President of the National Trust for Historic Preservation,

“We can’t build our way out of the global warming crisis. We have to conserve our way out. That means we have to make better, wiser use of what we have already built.”

With replacement windows, it’s all or nothing. We can do as little or as much as needed with repair and restoration work. Services like replacing broken panes and cords are inexpensive and quick. Even with complete restoration, our services are often less costly than wasteful window replacements.

Chances are your windows have done their job for 50 or more years already. Sure, they might be a little creaky and may not be as attractive as they once were, but it’s a far better investment to repair a proven performer than to sink money into a new window that only has a 20-year warranty at best. With proper maintenance, your antique windows should last another 100 years.


“The SLIP Was A Game Changer For Me And My Family.”


It’s ingenious and I would recommend it to anyone who’s wanting to keep their vintage windows but upgrade their insulation. I’m a PNW gal and they’ve just made a world of difference. Thank you Chosen for the great product – I couldn’t be happier!


“Very Good Product”


11 out of 10 these guys are very knowledgeable and they have a very good product their installers are excellent craftsmen I would definitely recommend them for all of your vintage wood window needs.


“Hats Off To These Guys!”


This product is amazing!! I live in a house built in 1930’s and Chosen was able make my windows more efficient, saving me money each month on my electrical bill.


“Would Give A Sixth Star If Possible!”


Wonderful product for my wood windows. Friendly associates.