Introduction
Using storm windows can increase your home’s energy efficiency, reduce drafts and glare, block out outside noise, and make your home feel more comfortable.
Why
Windows are less insulating than the rest of the wall. Older single-pane windows and clear-glass double-pane can be drafty, get condensation and even frost build-up in winter, and feel drafty or cold when you sit next to them. Adding exterior storm windows can help block heat transfer so your home will feel warmer in winter and cooler in summer. They can also cut drafts, glare, and outside noise, making your home more comfortable as well as more efficient.
What You'll Need
- New high-performance exterior storm windows with low-emissivity coatings
- Exterior-grade caulk or sealant
- Screws and screwdriver
- Ladder
1. Examine existing windows.
Before buying new exterior storm windows, examine the condition of the existing windows.
- If the existing window shows excessive deterioration or damage, then full window replacement may be required.
- Peeling paint, cracks, or rotten wood at the sills or window trim is often a sign of water intrusion somewhere above or around the window. If you’re seeing signs like this, plan to remove the trim to investigate. You may need to remove the window to do repairs and re-install or replace the window.
- To reduce the potential for condensation between the existing window and the storm window, minimize air transfer by making the existing window as airtight as possible. Examine seals and weather stripping around the window perimeter and replace or repair as needed.
2. Consider your options.
Storm windows can be installed on either the interior or exterior of the existing window. Some windows are fixed glass, meaning they can’t be opened (unless the whole window swings open like the casement style windows shown in Figures 1 and 2). Some windows are operable, meaning they can be raised and lowered or slid to the side like the existing window (Figures 1 and 2), and permanent or removable varieties.
- Consider models that are certified by ENERGY STAR and the Attachment Energy Rating Council (AERC) for your climate zone (Figures 3, and 4).
- Look for storm windows that have low-emissivity (low-E) coatings. Low-e coatings significantly improve the thermal performance of the window and reduce the amount of solar heat gain through the window. Low-E storm windows cost about the same as standard storm windows but are about 50% more energy efficient than traditional uncoated storm windows (Cort 2013).
Source
Website developed by the Attachments Energy Rating Council to provide consumers with credible, relevant, and comparable information about window attachments and their performance.
3. Install.
1. Select models that have built-in weatherstripping and/or gaskets between the storm window and the existing window frames.
2. Follow manufacturer’s installation instructions, typically:
- Use the storm window manufacturer’s instructions for measuring and ordering the windows.
- Match the current opening style of your existing windows to ensure operability and egress (every bedroom needs a window or door that opens to the outside) .
- Place the window into the opening to ensure proper fit, then remove (Figure 5).
- Apply exterior-grade caulk or sealant to the existing window frame where the sides and top of the storm window will be mounted. Do NOT caulk the bottom, in order to not block the weep holes and drainage gap in the new storm windows (Figures 6 and 7).
- Mount and screw the storm window into place following manufacturer guidance (Figure 8).
- Many storm windows have an adjustable bottom leg to account for variations in the sill height; this should be adjusted as necessary.
- Contractor installation is advised for upper-story installations.
Source
4. Maintain performance.
To minimize possible condensation between the panes, the original window must be as airtight as possible (Wilson 1960). If the existing interior window is made sufficiently airtight, then the slight amount of ventilation provided by the storm windows’ weep holes should be adequate air change to prevent condensation while also maintaining the windows’ thermal performance.
If condensation does appear on the storm windows, take the following steps:
- Make sure the weep holes are clear.
- Slightly increase the openings to allow for additional ventilation.
If condensation persists, consider the following additional steps to control indoor sources of humidity:
- Add timers or humidity sensors to bath exhaust fans and advise occupants to run exhaust fans when showering or cooking.
- Dry clothes outside or in the clothes dryer; hang-drying clothes indoors adds a considerable amount of moisture to the indoor air.
- Ensure that the exhaust fans and clothes dryer are ducted to the outside, not into the attic or crawlspace.
- Verify that the crawlspace floor is covered with a continuous vapor barrier that covers the entire floor and is secured to the walls and that the sump pump basin is covered with a tight-fitting lid. Or, address any basement moisture issues.
- Run a dehumidifier if needed.
