Home Energy: Storm Windows

Even well-sealed windows lose heat through the glass. Storm windows add an extra layer of insulation by trapping air between the existing window and the storm layer. This dead air space (ideally between ¾ to 4 inches) acts as a thermal buffer, reducing heat transfer and minimizing drafts. A well-sealed storm window can also reduce condensation, which helps prevent frost buildup during cold Maryland winters. New models can also reduce noise, and many are permanently mounted and operable, unlike older seasonal versions.

Given Maryland’s humid summers and chilly winters, storm windows offer year-round benefits. They help retain warmth during heating season and can be removed or opened for ventilation in spring and fall. For historic homes or rental units, interior-mounted options provide flexibility without altering exterior aesthetics.

• Cost-effective, affordable, and DIY-friendly, these kits use clear plastic films (vinyl, polyester, or polyethylene) mounted inside or outside the window.
• Thicker films are easier to handle and more durable.
• Best for renters or multi-story homes where exterior access is limited.
• For best results, use a hair dryer to shrink the film for a tight seal.
• Mounting options include tacking, stapling, or using reusable frames or tracks available at hardware stores. Mounting tracks allow reuse of frames each winter.

• Use low-emissivity (low-E) plastic for better insulation.

  

• Made from acrylic (e.g., Plexiglas®), these are more durable and visually similar to glass.
• Ideal for interior mounting, especially in multi-story homes or apartments.
• Lightweight, durable, and easy to cut, but prone to scratching.
• Mounting kits with magnetic or adhesive frames are widely available and improve air sealing.
• New designs include flexible gaskets for snug, press-fit installation.

• These permanent exterior-mounted units feature glass panes and insect screens.
• Look for ENERGY STAR® certified models with welded corners, weatherstripping, and operability.
• Typically made with aluminum frames, they allow for natural ventilation.
• Look for quality features like welded corners, weatherstripping, and warranties.
• While more expensive, they offer convenience and curb appeal.
• Low-E coatings reflect heat indoors during winter and block solar gain in summer.

• Interior-mounted options are easier to install and maintain, especially in urban or multi-level homes.
• Ensure the primary window is sealed with caulk and weatherstripping before adding a storm layer.
• Weatherstrip the storm window itself to maximize energy savings and reduce moisture issues.
• Use storm windows with weep holes to prevent moisture buildup.
• Avoid silicone caulk for exterior mounting. Opt for butyl or elastomeric caulk for easier future repairs.

• ENERGY STAR® certified storm windows may qualify for federal tax credits up to $600 under the Inflation Reduction Act. [Learn more at: ENERGY STAR; IRS Form 5695]
• Maryland’s BeSMART Home Loan Program offers up to $30,000 in low-interest financing for energy-efficient upgrades, including storm windows. [Learn more at: MEA; MD DHCD]
• Weatherization Assistance Programs may provide free or low-cost storm window upgrades for income-qualified households. [Learn more at: Maryland OPC]