The All-In-One Historic Window Insulation Retrofit.
Window SLIP is the complete sash-mounted thermal upgrade for historic windows. This precision-fabricated system, built to spec and delivered ready for professional installation, is complete with all required components and labeling.
Our Clients






Window Pane Retrofit Kits Are Often Unnecessarily Complicated
On the job retrofitting wood windows, adding better insulation, or upgrading to a new window– contractors often spend too much time hunting down the hardware needed to complete the job. This costs you and in turn, your client, too much money for what could be a simple job.


Most Window Insulation Solutions Aren’t Built With You In Mind
- Home improvement stores sell temporary fixes
- Other insulation products on the market force you to hunt down additional supplies to complete the job
- These store-bought options lack a guarantee for success, and homeowners are forced to purchase new products every season.
- Professionals need a contractor-grade solution that is a permanent fix for their clients.
Designed By Contractors For Contractors
Custom-made to fit each project, we created a system designed to work for contractors and their clients.
- Unlike store-bought solutions, SLIPs are custom-fabricated for each sash, ensuring precise fit and optimal performance.
- Each system includes mounting fasteners and optional components such as weatherstripping and hidden balances. For historic windows with existing weight-and-pulley hardware, SLIPs can be adapted to preserve those original mechanisms.
- Our goal is to support your install method — whether you’re restoring traditional joinery or upgrading to modern concealed hardware — with a permanent, energy-efficient solution
- We guarantee the quality of our products. They’re tested and provide similar energy efficiency as EnergyStar-certified alternatives.
- Our Window SLIP System gives you the tools you need to provide a beautiful solution to older, drafty windows.

Testimonials
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.

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.

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.

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
Leaded Windows
Stained Glass Windows
Arched Windows
Window SLIPs can be custom-fabricated for arched windows for a cost-effective insulation solution for beautiful historic windows.
Fully Customized To Your Exact Specs
We create each Window SLIP to order from products made in the USA. To ensure good quality, we ask you to provide the measurements of each window. We make them individually to fit the unique sash of each historic and vintage window.

Bulk Orders & Commercial Projects
For larger buildings and projects, we’re happy to work with you to create Window SLIPs in bulk. Whether you’re working in commercial or industrial settings or with residential customers, we’re here to help.

Customization for Residential, Commercial, and Industrial Needs
We’re able to create SLIPs for curved windows, handle custom paint colors, and assist with installation on large-scale projects as well. Contact us for more information about our offerings for your project.
We Provide Step-By-Step Installation Training
From window prep to maintenance, we provide literature and video tutorials on how to properly install our Window SLIPs. When you place your order, you’ll receive access to a comprehensive video detailing the installation process. Of course, you can also contact our team for any questions you may have before, during, or after installation.
Woodworking and technical skills are needed to successfully install our Window SLIPS. This is why we work directly with contractors, architects, and advanced DIYers only.
What You’ll Find With Each System
Each system is sent via freight shipping directly to you with each Window SLIP securely packaged and labeled.
Your Custom SLIPs
Each custom slip will arrive labeled with the exact location it’s custom-made for, so you can easily see which windows go to the living room and which belong in the kitchen. The hardware to pair with each will also come labeled.
All The Hardware You Need
No additional hardware store runs are needed, our systems come with hardware including weatherstripping, hidden balances, screws, and tabs labeled with their window pairings as well. We make it easy for you to impress your customers with a fast and efficient install!

Frequently Asked Questions
How Do I Become a Certified Installer for Window SLIP?
Do You Offer Bulk Pricing for Contractors or Commercial Clients?
What is the Shipping Time for Bulk or Custom Orders?
Our typical order turnaround time from placing the order to delivery is 8-10 weeks. For extra-large or customized orders, that may change. Contact us with the details for your project for the most accurate quote on how much time we’d need to produce and ship your SLIP system.
Still have questions? Check out our Frequently Asked Questions page for more information.
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.
Contact Us Today to Get Started
With decades of experience repairing, retrofitting, and restoring wood windows, we’re the industry experts. We’ve designed Window SLIPs to meet the unique needs of contractors working on historic residences and businesses. To improve energy efficiency, see a reduced heating bill, and maintain the historic charm of vintage windows, contact us for a FREE quote today!