Storm windows are hardworking house add-ons that defend against the elements and make homes more energy-efficient. Most commonly used on single-pane windows, storm windows act as moisture barriers, heat retainers, sound-proofers, and protectors of existing windows' millwork, glazing, and seals.
Because they are affordable, functional, and available in an array of styles, glazes, and materials, exterior and interior storm windows are often chosen as a budget-friendly alternative to more expensive replacement windows. Most exterior storm windows, which are mounted to the outside of a house, are easily installed by handy do-it-yourselfers. Interior storm windows are simple inserts that require nary a carpentry skill.
Your home's architectural style, your budget, and your DIY skills will steer your choices as you shop for storm windows. This guide, which details storm window types, installation instructions, and maintenance advice, will help you sort through your options.
There are three basic types of storm windows: interior storm windows, temporary storm windows, and exterior storm windows.
Interior storm windows are inexpensive lightweight plastic, acrylic, or glass inserts that can be quickly installed and removed and also customized to fit uncommon window sizes and shapes. Some are simple panels; others are units framed in vinyl or fiberglass. Some attach with magnets; others via compression. Interior storm windows are designed to fit snugly inside interior window frames; their tight seal optimizes their insulating and sound-reduction qualities. Interior storm windows' ease of installation makes them good choices for apartments and homes with multiple stories.
Temporary and disposable storm windows come into play primarily during the coldest months. Disposable types are available as single acrylic panels that fit inside a window's pane. Temporary storm windows can be created using insulating films that attach to a window's interior face with adhesive tape and are shrunk with a hair dryer to create a tight seal.
Exterior storm windows are available in various configurations, standard window sizes, and with wood, aluminum, or vinyl frames.
Energy Saver, the U.S. Department of Energy's resource for consumers, notes that aluminum storm windows are strong, light, and nearly maintenance-free, but they're poor insulators because they heat up quickly.
Wood storm window frames—like those on older homes, which are put up and taken down with changing seasons—are good insulators but heavier than metal frames. Wood frames expand and contract during hot and cold temperatures, which influence how tight they fit; they also become weathered over time. Newer vinyl- or aluminum-clad wood-frame options require less maintenance than exposed-wood frames.
Lightweight vinyl storm window frames are constructed with stabilizers that prevent sunlight from adversely affecting their strength; too much sunlight may cause some frame colors to fade. High temperatures may cause warping; below-freezing temps may create cracks.
Today's exterior storm windows—unlike old-timey versions that are switched with screens come summer—are available as two-track, triple-track, two-track slider, and basement (picture) storm windows. Lowe's Storm Window Buying Guide details each type. Here's a summary of readily available storm windows.
A two-track configuration—which is used for double-hung windows—has an outer track that contains a half-screen on the bottom and an outer glass pane on the top. Neither screen nor pane slides up or down. The inside track contains an inside pane, which can be raised to allow fresh air to enter through the screen.
A triple-track storm window—which is designed for double-hung windows—is configured with two window panes and a half-screen resting in separate tracks, which allows each component to move singly and lets you move the screen section to the top and windows to the bottom to better capture breezes.
A two-track slider storm window—which works with slider-type windows—operates like a two-track storm window but in a horizontal fashion.
Basement or picture-style storm windows are long, narrow rectangles that boast a single pane of glass, which is secured with thumb latches.
When shopping for exterior storm windows, the window experts at Lowe's say you should check that corner joints overlap for strength. Overlapped joints are preferable to mitered corners, which aren't as strong and may allow air to seep through. Quality storm windows should also have adjustable ventilation stops on the inside track and glass and screens that can be removed for easy cleaning. The frames should sport predrilled holes to ease installation and good weather-stripping features that make windows as airtight as possible. For increased energy-efficiency, opt for windows with low-emissive (low-E) glass. The treated glass keeps heat out while letting natural light flow inside.
It's important to measure each window that you plan on outfitting with an exterior (or interior) storm window. Taking individual measurements ensures the new storm windows will properly fit every window. Determine the width by measuring across the window from inside molding to inside molding; take a measurement at the top, middle, and bottom of the window. Write down the narrowest measurement. Determine the height of each window by measuring from the top inside molding to the sill. Take measurements on the right and left sides and at the center; write down the shortest measurement. The smallest height and width measurements guarantee that the new storm window's flanges will fall where they need to on the window's exterior trim.
As noted before, interior storm windows are simply inserted into the interior-facing windows and held in place by magnets or compression. But installing exterior storm windows requires a few DIY skills and being comfortable working on a ladder. If you're not up to the task, call in a window-installation company or check at your favorite home center for an installer who will come out and measure, order properly sized storm windows, and install them when they arrive at the store. As with any remodeling job, get multiple bids and check contractors' references.
Ready to tackle the job yourself? Follow these edited instructions from Energy Saver.
Before hanging new storm windows, make sure the primary windows and surrounding trim are dry, in good shape, and in working order. Fix any flaws and replace missing parts.
Position the storm window in the opening to check for proper fit. Determine the storm window's top by noting which direction the movable panels (if applicable) operate. Center the storm window in the opening. Check that all screw holes land on solid wood. Remove the storm window.
Caulk the top and sides of the existing window opening. Do not caulk the bottom sill. Reposition the storm window in opening. Push the top of the storm window snugly into the top of the opening.
Begin securing the storm window to the window frame. Use a screwdriver and screws to temporarily secure the top corners of the storm window. Adjust the expander on the bottom of the storm window (the windowsill expander allows the bottom of the storm window to expand about 1/2 inch to meet the angled sill of the window opening). Use a putty knife to tap the expander tight and evenly against the windowsill.
Square the storm window unit and install the remaining installation screws. Make sure the gap between the window and the frame is even (the ideal gap is 1/16 inch on each side of the window).
Regular cleaning will ensure your new storm windows endure for decades to come. Interior storm-window inserts can be removed and simply wiped down with a soft cloth and window cleaner. For exterior storm windows, open interior windows, vacuum debris from interior sills, and dust off reachable panes and screens; use a broom to sweep dirt from the outside of the windows. Once a year (on a cloudy day to deter streaking!) remove the exterior storm windows and set them across pairs of sawhorses or against an exterior wall or fence. Hose them down and clean with soapy water, rinse off soapy residue, let them dry, and reinstall storms. Once they're back in place, use paper towels and glass cleaner to shine them up and remove fingerprints, streaks, and smudges.