The Problem with Window Inserts & Why You Need Real Insulated Windows

November 26, 2016

The main problem with Window Inserts (interior storm windows) is that they are simply no substitution for high quality, energy efficient, insulated glass windows. Let’s get this out of the way immediately; I’m not a big fan of interior storm windows!

While window inserts can be a lower cost, easy fix, for the DIY homeowner, window inserts simply don’t stack up to the insulation value of quality insulated glass. Another huge problem with window inserts is the potential for condensation build up between the insert itself and your original windows.

What Causes the Condensation Problem with Window Inserts

Sometimes the condensation problem with window inserts is related to other issues within your home. The window insert just brings the issue to light. Here are some things to look for:

Excessive Sealing: While you don’t want the winter wind blowing through your home, you also don’t want your house buttoned up so tight that it can’t ventilate. In particular, your home requires adequate ventilation in high moisture areas such as bathrooms and kitchens to allow the moisture to escape.

Extreme Temperature Changes: The temperature of the airgap should stabilize over time. If there is a sudden swing in temperature, such as the first cold day of winter, condensation may form in the airgap. In this case the moisture may dissipate once the space acclimates.

Poor Perimeter Seal: To avoid a condensation problem with window inserts you need a suitable air-tight seal around the entire perimeter of the unit. Look for protruding screws which may damage the seal and cause an air gap where moisture from your home can enter the air gap can create condensation.

Pulley Holes: The original window may have places where air can leak from within the walls of the home such as pully holes. You should also take a close look at the underside of the interior window sill. Quite often contractors will fail to caulk this area properly. This is place where interior can be drawn into the gap between the insert and the window. Taking time to properly caulk this area may solve the problem.

Last Resort

If all else fails, you may need to crack open the outside window so the cavity vents a little to let the moisture escape. A word of caution here though. Don’t open the window more than a sliver or you will defeat the purpose of creating the air gap in the first place. The space between the window and the insert must stay somewhat warm to create an insulating barrier. If you’re old enough to remember the old-style storm windows, most of them had a teeny tiny ventilation hole at the bottom which was sized just right to let a smidgen of air escape. (“smidgen” – a small amount of something!)

Contact Us:

If you are looking for insulated glass windows to replace your inadequate window inserts give us a call and we can take care of you? Contact One Source Renovation, LLC at or give us a call at (815)-634-8922.