Regular vs Storm Windows: Key Differences

Regular windows are single- or double-pane units designed primarily for light, ventilation, and basic weather protection, while storm windows are an additional, removable layer installed on the interior or exterior of an existing window to improve insulation and protect the primary window from severe weather. Storm windows add an extra pane of glass (or plastic) and an air gap that reduces heat loss, drafts, and noise, and they can also shield the main window from wind, rain, and debris.

What Are Regular Windows?

Regular windows—also called prime or primary windows—are the main glazed openings in a building’s exterior wall. They come in a wide range of styles (double-hung, casement, sliding, awning, fixed) and materials (vinyl, wood, aluminum, fiberglass). Modern regular windows often have two panes of glass (double glazing) with a sealed air or gas fill between them, plus low-emissivity (low-E) coatings and insulated frames. Their primary job is to let in light and air, provide a view, and serve as the building’s main weather barrier.

Regular windows are permanently installed and are the first line of defense against outside temperatures. Their performance is measured by the U-factor (how well they resist heat flow) and the Solar Heat Gain Coefficient (SHGC). A lower U-factor means better insulation. For example, a typical new double-pane window has a U-factor around 0.30, while an old single-pane window might be 1.0 or higher.

What Are Storm Windows?

Storm windows are secondary glazing units that are installed over an existing window—either on the inside (interior storm windows) or on the outside (exterior storm windows). They are not a replacement for the primary window; they add an extra layer of glass, acrylic, or plastic that creates a dead air space between the storm pane and the original window. This trapped air acts as an insulating buffer, reducing heat transfer and air leakage.

Storm windows are often used in older homes where the original single-pane windows are historically significant or too costly to replace. They can also be used on new windows to boost energy efficiency in extreme climates. Exterior storm windows are typically made of glass and aluminum frames, while interior versions are often acrylic or glass panels that mount inside the window frame and are removable for cleaning.

How They Differ in Performance

The most significant difference is in how they achieve insulation. A regular double-pane window has two panes of glass sealed together with a spacer and gas fill (often argon or krypton) to reduce heat transfer. A storm window adds a third pane (or a second pane if the primary is single-pane) without replacing the original. The air gap between the storm window and the primary window is not sealed as tightly as a factory-sealed insulated glass unit, but it still provides a meaningful reduction in U-factor.

For example, adding an exterior storm window to a single-pane window can reduce the U-factor from about 1.0 to around 0.50, cutting heat loss roughly in half. Adding a storm window to a double-pane window can lower the U-factor from 0.30 to about 0.20. Storm windows also reduce air infiltration—the drafts around the primary window—because they add a second weather barrier. They can also reduce outside noise by an additional 5 to 10 decibels, depending on the glass thickness and air gap.

Installation and Maintenance

Regular windows are installed directly into the wall opening and are meant to stay in place for decades. They require occasional maintenance like cleaning, lubricating tracks, and replacing weatherstripping. Storm windows are usually installed over the existing window frame, either from the inside or outside, and can be removed seasonally if needed.

Exterior storm windows are often mounted with screws or clips and may have a screen that can be swapped in for summer use. Interior storm windows are held in place with tension clips or magnetic strips, making them easy to install and remove. Maintenance for storm windows includes cleaning the extra pane and checking the seals. One common issue is condensation forming between the storm window and the primary window, especially if the primary window is not well sealed. To reduce this, many storm windows have small vents that allow moisture to escape.

Cost and Energy Savings

Storm windows are generally much cheaper than replacing the primary windows. A typical exterior storm window costs $50 to $150 per window (material only), while a new double-pane window might cost $300 to $800 or more installed. Interior storm windows can be even less, especially if you choose a DIY kit with plastic film.

Energy savings depend on your climate, the type of primary window, and the storm window’s quality. The U.S. Department of Energy estimates that storm windows can reduce heating and cooling costs by 10% to 30% in older homes. The payback period varies, but for a single-pane home in a cold climate, it can be as short as a few years. However, if your primary windows are already double-pane and in good condition, the additional savings from storm windows may be modest.

Common Problems and Misconceptions

A common misconception is that storm windows are only for cold climates. They also help in hot climates by reducing solar heat gain and insulating against outside heat. Another misconception is that storm windows always look ugly or block the view. Modern exterior storm windows are available with low-E glass and slim frames that are barely noticeable from the outside. Interior storm windows are virtually invisible from the outside.

One common problem is condensation between the storm window and the primary window. This happens when warm, humid indoor air reaches the cold surface of the primary window and condenses. To prevent this, the primary window should be well sealed, and the storm window should have small vents to allow moisture to escape. Another issue is that some exterior storm windows can interfere with the operation of the primary window if not installed correctly. For example, a storm window on a casement window may block the crank mechanism.

How to Choose Between Them

Choosing between regular windows and storm windows depends on your goals and budget:

If your existing windows are single-pane and in good condition: Adding storm windows is a cost-effective way to improve energy efficiency without the expense of full replacement.
If your windows are old, drafty, or damaged: Replacing them with new double-pane windows may be the better long-term investment, especially if you plan to stay in the home for many years.
If you live in an area with severe weather (hurricanes, tornadoes, high winds): Exterior storm windows with impact-resistant glass can provide extra protection for the primary window.
If you want to preserve historic windows: Storm windows allow you to keep the original windows while improving their performance.
If you are on a tight budget: Interior storm windows or even plastic film kits are the cheapest options, though they are less durable and less effective than glass storm windows.

It’s also possible to combine both: install new double-pane windows and add storm windows in extreme climates for maximum efficiency. However, this is rarely necessary unless you live in a very cold or very hot region.

Frequently Asked Questions

Can I install storm windows over double-pane windows?

Yes, you can. Adding a storm window over a double-pane window creates a triple-pane effect, further reducing heat transfer. The improvement is smaller than when adding to a single-pane window, but it can still help in extreme climates and reduce drafts.

Are storm windows worth it if I already have new windows?

Usually not, unless you have specific issues like excessive noise or very cold winters. New double-pane windows are already well insulated, and the additional savings from storm windows may take many years to recoup the cost.

Do storm windows cause condensation?

They can, if the primary window is not well sealed and warm indoor air reaches the cold outer pane. To prevent this, ensure the primary window is sealed and use storm windows with vents to allow moisture to escape.

Can I leave storm windows on all year?

Yes, you can leave them on year-round. Many exterior storm windows have screens that can be swapped in for summer, but the glass panels can stay in place. Leaving them on also provides protection from summer storms and reduces heat gain.

Do storm windows reduce noise?

Yes, they add an extra layer of glass and an air gap, which helps dampen outside noise. The effect is similar to adding a second pane to a single-pane window. For best sound reduction, choose storm windows with thicker glass and a wider air gap.

Are storm windows the same as impact windows?

No. Impact windows are specially designed primary windows with laminated glass and reinforced frames to resist flying debris during hurricanes. Storm windows can provide some protection, but they are not a substitute for code-compliant impact windows in hurricane-prone areas.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

More in this bed

The whole Tech How-To bed →