Wood Window Insulation Inserts.
High-Performance Window Upgrades for Wood Sash Windows. Eliminate drafts and improve efficiency with a sash-mounted glass system built for preservation and performance.
The Beauty,
Enhance
The
Function
Our Clients
When the Frost Comes, Well-Insulated Windows are Your First Line of Defense
Single-pane wood windows are a major source of heat loss in older buildings. Our sash-mounted glazing system delivers lasting thermal performance — eliminating seasonal air leaks and reducing heating bills without the need for replacement. It can impact your comfort, to be sure, but it also impacts your wallet with higher energy costs.
Historic Windows Look Beautiful, But Lack the Modern Insulation You Need
Vintage windows often have ornate craftsmanship that is difficult and expensive to recreate in a replacement.
Historic windows are often built with dense old-growth wood and intricate joinery — qualities that outperform modern replacements when properly maintained. Our SLIP system adds a secondary glazing layer to the existing sash, dramatically increasing efficiency while retaining the window’s original character and operability.
Cold air finds its way in, and temporary solutions don’t provide enough insulation. And they often compromise functionality while in place.
Window SLIPs are a Permanent Solution to Improve the Comfort of Your Home
We’ve created a permanent solution that preserves the look of historic windows with the energy efficiency you need.
- Window SLIPs stop drafty windows in their tracks without hiding the beauty of the original window.
- As a permanent solution, you can relax knowing you won’t need to adjust your window insulation seasonally.
- SLIPs provide efficiency on par with double pane replacements and test far higher than DIY options.
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
Double-Hung Windows
Casement Windows
Leaded Windows
Stained Glass Windows
Arched Windows
Window SLIP vs Traditional Wood Window Inserts
Unlike traditional inserts or temporary storm products, SLIP is a permanent secondary glazing system installed directly to the sash. It delivers lasting energy efficiency, preserves operability, and blends seamlessly with the existing window
DIY Window Sash Inserts
There are a variety of window inserts on the market. On Amazon alone, you’ll find magnetic, plastic, quilted, foam, and even acrylic window inserts. These options are low-cost, but they don’t provide the same quality as Window SLIPs. These temporary fixes also require you to block daylight, avoid opening the window, and buy new products each year.
Window SLIP is Superior
Homeowners and Contractors agree that Window SLIPs are the perfect solution for a vintage home. If you aren’t willing to sacrifice maintaining the rich history of your home’s architecture for the functionality of the heating and cooling systems, SLIPs are perfect for you. They allow you to open your windows, keep all of your natural light, and prevent frost from impacting your cozy home.
Testimonials
Why Choose Inserts Vs Window Replacement?
A custom, aesthetically pleasing answer to drafty and difficult-to-replace windows. SLIP adds a pane to each sash, either interior or exterior, retaining the original window glass. Enjoy your original architecture with this cost-effective, energy-efficient solution!
Preserve Historic Windows Without Compromising on Efficiency
Maintaining the charm of historic buildings is something we’re passionate about. Working on repairing, restoring, and retrofitting wood windows is what led us to create the Window SLIP. We wanted a solution that showcased the beauty of historic window details while preserving them for decades to come.
The Most Eco-Friendly Upgrade Uses What You Already Have
If you’re looking to increase the energy efficiency and sustainability of your home, SLIPs are a great option that allows you to use the windows you already have. Maintaining the things we have and taking care of them for the future is something we find to be very important. SLIP helps craft a greener future for our homes and our planet.
The Value Is Clear
When you look at these windows, you may not see much of a difference, and that’s the point! Whether in small casement window applications or larger sizes, our SLIPs fade into the background to let your windows shine through.
Energy Performance Comparison: Window Upgrade Types
| Window Upgrade Type | U-Value Reduction | Estimated Energy Bill Savings | Notes |
|---|---|---|---|
| Weatherstripping only | 18% | ~32% of window-related energy costs | Simple, low-cost improvement |
| SLIP system only | 26% | ~73% of window-related energy costs | Tested in UO study |
| Double pane replacement | 28% | ~76% of window-related energy costs | Requires full window removal |
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.
Get the Best Window Insulation Inserts on the Market
We are your trusted partners in historic window insulation and inserts. Get in touch today to start the process of creating custom SLIPs that eliminate those drafts for years to come. We appreciate your consideration of our products and hope you’ll contact us today with your window measurements to get a free quote!