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Non-Invasive Insulation Solutions for Historic Windows.

Stretch your business’s budget further with Slim Line Insulation Panes.

Exploded diagram of a window with WindowSLIP system, showing how the insert fits over the original window frame.

Order Your Customized SLIP System

Illustration comparing a traditional storm window on the left and SLIP™ window on the right, showing differences in design and structure. The traditional storm has a simpler outline, while SLIP™ features a more complex design.

Follow Our Simple Installation Process

Standalone WindowSLIP insert with a beige frame and two clear glass panes.

Enjoy The Results

Our Clients

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Tired of Drafty Single-Pane Windows?

Historic buildings are charming places to establish your business, but often come with windows that aren’t up to today’s standards. Single-pane windows let warm air out in the winter months and cold air in during the warmer months. You’ve probably tried window films and other temporary solutions without success. But there’s good news, replacement is not the only option! Our Window SLIPs provide an extra layer of insulation without obstructing the charm of your historic windows.

Two large, arched single-pane windows in a red brick building, suggesting potential draft issues.

No Fog or Haze

Energy Saving

Low Profile

Your Business Could Be Paying up to 72% More Than You Need to in Energy Costs

  • Older Single-Pane window glass is prone to heat loss and heat transfer.
  • Without proper insulation, energy bills go up as your HVAC works harder to maintain a comfortable temperature.
  • Heat gain and heat loss through windows are responsible for 25%–30% of residential heating and cooling energy use.
  • Quick fixes like window insulation film are temporary solutions. You have to buy them over and over again, and that adds up.
Sunlit Room with Ladder
Red brick building with arched windows featuring WindowSLIP installed, white trim detailing, and a central chimney.

Window SLIPs Are a Cost-Effective Solution for Businesses in Historic or Older Buildings

SLIPs mount to the existing sash, not over it, creating an insulated, sealed unit without altering visual appearance or functionality. Unlike storm panels or inserts, SLIPs are permanent and professionally installed.

  • Maintain the look and feel of your charming historic windows without compromising on the comfort of your business.
  • Not only is the installation of Window SLIPs a much more affordable option vs. full replacement, but you’ll save up to 72% on heating costs.
  • Single pane windows with an added SLIP are rated as well as EnergyStar Certified double pane windows, and you’ll enjoy the best results.

Why Choose Us

Window SLIP is part of Chosen Wood Window Maintenance. A premier residential and commercial, full-service window contractor– our team has decades of experience in window restoration and repair. We’re passionate about maintaining the beauty of historic homes and businesses. That drove us to create Window SLIP as a great option to improve efficiency without compromising the charm of older windows.

How Do Our Window SLIPs Work?

Window SLIPs are custom-made to fit the exact specifications of your residence or business. They are installed by contractors, architects, or licensed professionals. Because of their slim lines and clear glass– they’re nearly invisible once put on your window.

Illustration comparing a traditional storm window on the left and SLIP™ window on the right, showing differences in design and structure. The traditional storm has a simpler outline, while SLIP™ features a more complex design.

Custom Fabrication

Each SLIP is custom-fabricated to match the daylight opening of the sash and mounts securely to the interior or exterior face of the sash, depending on configuration. The system includes a slim-profile aluminum frame and high-performance glass, installed by trained contractors or preservation professionals. The low-profile frame can be painted to match your window and disappear. This allows your original window to show through as if no alterations were made.

Exploded diagram of a window with WindowSLIP system, showing how the insert fits over the original window frame.

Professional Installation

Windows remain fully operable, and in some cases, painted-over or damaged windows can be fixed utilizing Window SLIPs. Our systems come with all installation hardware included. In your package you’ll find hanging balances, weatherstripping, screws, and tabs.

Questions about Installation? Check out our Frequently Asked Questions page or this how-to video.

Standalone WindowSLIP insert with a beige frame and two clear glass panes.

Energy Saving Benefits

The homeowners experience all the benefits of double-pane windows, without the price tag of full replacement. Our customers report cost savings of over 72% on their energy bills. They also notice reduced noise and no more moisture.

What Types of Windows Can We Create SLIPs For?

Single Pane Windows

Window SLIPs add a second layer to single-pane windows, creating insulation similar to double-pane quality.

Single-Hung Windows

Windows with a single fixed sash and one operable sash can easily be fitted for window SLIPs while maintaining functionality.

Double-Hung Windows

Double-hung windows can be fitted for SLIPs while keeping the windows functioning properly.

Casement Windows

Our Window SLIPs can be fitted to casement windows without impacting the hinges, allowing for the full range of motion.

Leaded Windows

Window SLIPs are a perfect solution for beautiful leaded windows. Maintain the look and feel, with increased insulation.

Stained Glass Windows

Protect your stained glass windows for years with SLIPs that add insulation and protection from the elements.

Arched Windows

Window SLIPs can be custom-fabricated for arched windows for a cost-effective insulation solution for beautiful historic windows.

Get a Free Quote

Contact us today to level up your window insulation with cost-effective SLIPs. Simply provide your window measurements to receive a customized quote. For larger commercial projects, we’re able to accommodate curved windows, custom paint, and more!

Case Studies

We Put Our Window SLIPS to the Test

We participated in testing with the University of Oregon with their Energy Studies In Buildings Laboratory to compare different methods of vintage window insulation. They wanted to determine which would be the best method for historic Straub Hall on campus.

The Insulation Options Tested

The University team compared four single-pane window insulation solutions to compare quality:

 

  1. The original windows
  2. The windows with one layer of insulated film
  3. An insulated glass conversion
  4. Our Window SLIPs

The Results are Clear

Test results from the University of Oregon’s Energy Studies in Buildings Lab showed that SLIPs delivered thermal performance nearly identical to full insulated glass conversions, at a fraction of the cost, and with no loss of historic character. This outcome and the cost-effective price of Window SLIP led them to choose us for Straub Hall. We’re thrilled to hear that after years of occupancy, they’re still very happy with their decision:

“Based on the energy modeling that we did for the building, including live mock-ups, the study showed that the SLIPS were very close to the energy performance of the IGU option, and given the lower cost the decision was made to go with the SLIP system. We are now three years into occupancy and have had no issues with the windows. The SLIPS are very unobtrusive, and we were able to save hundreds of historic windows and still met our stringent standards of energy performance that exceeds Oregon State Code.”

George Bleekman, Owner’s Representative, Capital Design & Facilities Management

Brick building with grid-style windows and dried hydrangea bushes in front.

Frequently Asked Questions

Do You Provide Installation Services for Historic Commercial Buildings?

We work with contractors, architects, and certified installers for many projects. Our team at Chosen Wood Window Maintenance is available for installation and consultation for certain commercial projects. Inquire at sales@windowslip.com for more installation information.

How Much Can Businesses Save By Insulating Single Pane Windows?

Our customers see up to a 72% savings in their energy bills after installing SLIPs on their older windows. Many also report enjoying reduced noise, more consistent temperatures, and improved comfort. This is much higher than store-bought single-pane window insulation solutions, which save you only 5-10%, depending on your windows.

Will Window SLIPs Alter the Appearance of Historic Windows?

Our Slim Line Insulating Panels are intentionally as low-profile as possible to blend in with your historic windows. They are completely clear and sit just within your window frame. This provides excellent insulation with a nearly undetectable appearance.

Can I Just Caulk or Use Weatherstripping to Control the Temperature in My Office?

Older buildings are often drafty due to older single-pane windows that aren’t properly insulated. While you’ll find budget solutions at home improvement stores and find advice online to attempt hacks like bubble wrap or thermal curtains– they don’t provide the desired results. Many businesses believe the only permanent option is to fully replace the windows.

Our Window SLIPs provide the same quality insulation as double-pane windows at a fraction of the price. Utilizing your existing historic windows preserves the charm and character of your home.

Will Window SLIPs Fog or Become Hazy?

No, once installed, the vents built into the SLIPs should keep the windows from fogging. If fogging occurs, the fastening screws could be too tight, pinching the vents, and should be adjusted. Contact us for troubleshooting help if fogging persists.

Backed by a Ten Year Warranty

Our SLIPs are guaranteed to withstand regular wear and tear for a decade. We require professionals who install our products to provide a 1-year warranty on installation as well. With proper maintenance, our SLIPs can easily last for the life of your windows.

Set Your Business Up for Success

Your organization wants a permanent single-pane window insulation solution. Deliver the best product on the market with SLIP. We’re always here to answer questions for our Contractor partners and are happy to provide a free quote for your project. Simply send us window measurements and project details, and we’ll provide a quote for custom Window SLIPs.