Slim Line Insulating Pane

Drafty Windows? Lack of Energy Efficiency? Loss of Operation? Update your windows to modern standards.

If you’re tired of air, heat, and money flying out of the window (literally) then it’s time to check out the innovative Window SLIP™ (Slim Line Insulating Pane). You don’t need to get rid of your original vintage wood windows! In fact, many vintage wood windows can outlast today’s manufactured windows. The problems that vintage windows present when they’re not updated – drafts, low insulation, and little protection from the elements – are exactly what our product addresses, allowing you to retain the valuable integrity of your windows while enjoying modern standards!

This cost-effective product lets you keep your existing wood windows, but makes them more efficient, keeping you comfortable and saving you money! SLIPs are designed with form and function in mind, with a sleek look that makes it virtually invisible. The SLIP is attached directly to the sash, which is kerfed and weather-stripped to eliminate drafts and keep things nice and tight.

This incredible product provides fantastic insulating properties without having to alter the original glass in any way so you can retain your beautiful original wavy glass. SLIPs are comparable to insulated glass conversions, but with a very special benefit — SLIPs offer little to no maintenance costs; they have their own air vents which prevent them from failing as many insulated glass units do. Unlike glass conversions, you won’t need to worry about periodic glass replacement either, keeping things cost-effective and easy to maintain.

The SLIP has made it possible to add an additional tempered pane directly to each sash, overlaying your current glass setup. It’s perfect for insulating windows with single or multiple panes. This simple, yet effective solution gives new life to single-hung, double-hung, casements, picture windows, and more! We know convenience matters too, that’s why SLIPs on double-hung windows are installed with a hidden balance system to handle the added weight and to enjoy a smooth operation every time you need to open and close your window. With the SLIP™, your window sash remains fully operable, which means you don’t have the extra struggle of opening two sets of windows like you sometimes have to do with bulky storm windows. Plus, since this update is a year-long solution, you don’t need to hassle with reinstallation each season.

This unique, tested and proven solution to drafty windows has a slew of added benefits beyond its superb insulation properties. It also increases energy efficiency, reduces noise, lets you maintain your original window glass so that your windows can remain historically accurate and functional, and features an extremely low maintenance cost. SLIPs are a solid, well-designed product that is less expensive than a window replacement, and they often provide the option of exterior or interior install.

We’ve been working for over 20 years with building owners that want to find a way to maintain their authentic vintage windows without headaches and high costs. We listened and took action, creating a quality product that solves an array of problems like insulation, noise, and protection, all while maintaining the functionality and the original aesthetics of vintage wood windows at a reasonable price.

Ready to get SLIPs on your windows? You can buy directly from Window SLIP, use a certified installer in your area, or have a 3rd party contractor or handyman install them for you. To learn more about this amazing product and how you can make them your window solution, visit

By Old House Journal

Founded in 1973, Old House Journal is the original authority when it comes to old-house restoration, traditional house styles, period kitchens, bath & kitchen restoration, DIY projects, gardens & landscaping, and more-- from Colonial and Victorian through Arts & Crafts and Mid-century Modern homes. 

© Copyright 2021 Home Group, a division of Active Interest Media. All Rights Reserved.
P.O. Box 20730 Boulder, CO 80308