Storm windows are windows that are mounted outside or inside of the main glass windows of a house. Storm windows exist in North America, but are uncommon in continental Europe, where double, triple or quadruple glazing is prevalent. Storm windows can be made of glass, rigid plastic panels, or flexible plastic sheets; and may be permanently or temporarily mounted. They function similarly to insulated glazing. The term may also refer to a small openable flap found in the side window on light aircraft. In the United States, the older style of this window is often referred to as a "storm sash". On modern houses they serve on existing windows in order to improve their thermal insulation and soundproofing. Aside from insulation, storm windows provide an additional measure of protection for homes against damage to costly glass panes during inclement weather such as hail. On older houses, storm windows were installed in autumn when the window screens were removed; later homes had the pieces combined in one unit. Similarly, storm doors (also called "screen doors") allow similar energy savings for the necessarily less efficient primary doors –the screen allows for summer ventilation.

Energy upgrade

Modern storm windows are a typical energy upgrade solution for cold climates. They are mostly intended to improve the insulation value (R-value) of existing windows, especially single-glazed units.

Advantages and disadvantages

Storm windows can be very cost effective in cold climates. They are inexpensive, and can reduce heat loss by up to 50%, increasing the building's comfort and reducing the heating costs. They also reduce exterior air infiltration significantly. Storm windows are an inexpensive add-on: even the best storm windows—three track exterior windows with low thermal emission—will cost a small fraction of the price of standard replacement windows. Interior storm windows can, however, produce condensation and be visually obstructive; exterior storm windows can also have a negative visual effect. These aesthetic issues can be minimized by single line storm sashes, the incorporation of vent holes, and a properly sealed fit.

Types of Storm Windows

Storm windows are used as an additional layer of insulation and protection for existing windows and are available in various materials and configurations.

Material and Design

Glass Types

Storm windows come with either glass or acrylic panes. Glass panes provide better visibility and last longer, whereas acrylic panes are less breakable but can scratch more easily. Modern storm windows often feature low-e glass, which improves energy efficiency by reflecting heat.

Configurations

Installation

Installing storm windows can be a DIY project, requiring tools like a screwdriver, caulk gun, and putty knife. Proper installation ensures their effectiveness and energy efficiency.

Manufacturing process and applications

There are several laminated glass manufacturing processes: The first method utilizes two or more pieces of glass bonded between one or more pieces of plasticized polyvinyl butyric resin using heat and pressure. The second method uses two or more pieces of glass and poly-carbonate, bonded together with aliphatic urethane inter-layer under heat and pressure. The third type of laminated glass is interlaid with a cured resin. Each manufacturing process may include glass layers of equal or unequal thickness.