Choose New Storm Windows for Historic House or Building | Wisconsin Historical Society

General Information

Selecting Appropriate Storm Windows for Your Historic Building

Choose New Storm Windows for Historic House or Building | Wisconsin Historical Society

One way to improve the energy efficiency of the windows in your historic house or building is to add storm windows. Adding a well-fitted, exterior wood or aluminum storm window to each of your windows will do these three things:

  • Reduce heat loss from your window
  • Stop air infiltration through your window
  • Protect your primary window sash from the weather (the sash of a window was never intended to take a direct hit from the weather)

Most historic houses in Wisconsin originally had wood storm windows. Wood storms were advertised in late-1800s millwork catalogs as a way to save on coal costs. Most historic commercial buildings had an exterior storm bed even if they did not originally have exterior storm windows. Wood storms are the most historically accurate storm windows you can use on your historic house or building, but some aluminum storm windows still meet the Secretary of the Interior Standards for Rehabilitation.

Exterior vs. Interior Storm Windows

Exterior storm windows replaced shutters during the mid-Victorian era as a means to protect window sashes. Interior storm windows do not protect the primary window sashes from the harsh Wisconsin weather and condensation. Interior storms generate about double the average condensation of exterior storms. This condensation leads to deterioration of the window. Therefore, interior storms are only recommended for windows that open to the outside, such as casement, awning and hopper windows.  

Wood Storm Windows

EnlargeA well-maintained wooden storm window with metal storm hangers on top.

A well-maintained wooden storm window with metal storm hangers on top. Source: Bob Yapp

You can buy the traditional wood storms with separate wood screen windows from hundreds of small millwork companies. A high-quality wood storm window should be made with clear pine, cedar or cypress. These woods hold paint well and are dimensionally stable. Be sure the wood is treated with a preservative and oil primed. You can then paint the storms the color you prefer. Some manufacturers will also prime and pre-paint them for you. Check with the manufacturer for instructions on how to measure storms properly for your windows.

All joints in a wood storm frame should be full-through mortise and tenon joints. A mortise and tenon joint is designed to allow for contraction and expansion. Mortise and tenon joints should be held together with either stainless steel pins or wood pegs, but never glued. If a mortise and tenon joint is glued, the wood will split and the joint will come apart.

Some millwork companies offer a convertible wood storm/screen. These convertible storms look like traditional wood storm windows, but they have removable glass and screen inserts. When convertible storms are installed, the wood frame is left in place but the glass and screens are removed and installed into the wood frame from inside the house.

Aluminum Storm Windows

EnlargeAn aluminum storm window.

An aluminum storm window may also be appropriate - confirm the storm window has a flush mount to more closely resemble historic wood storm windows. Source: Bob Yapp

Aluminum storms offer these three benefits over wood storms:

  • Aluminum storms will not need a new coat of paint for 20 years.
  • Aluminum storms do not need glazing compound, which can deteriorate and must be  reapplied periodically.
  • Aluminum storms do not need to be removed and reinstalled seasonally.

Aluminum self-storing, triple-track storms have two panes of glass and one screen. The glass and screen panels lift and lower in one of three tracks.

When you are shopping for aluminum storm windows, choose a flush-mounted window to replicate the historic appearance of a wood storm window. A blind-stop storm window has a reveal at the sash perimeter that creates a new appearance your historic house never had. 

If you choose to buy aluminum storms, be sure to get storms with an extruded aluminum frame, which helps to prevent heat loss. These aluminum storms have an air gap in the frame that helps to stop the conduction of hot and cold air. Be sure the frames are butt jointed on the corners and not mitered. The glass should be 1/8-inch thick. Screens for high-quality aluminum storms should be either charcoal fiberglass or charcoal aluminum. This type of high-quality aluminum storm is considered "commercial grade."

If you decide to buy storms with low-e (low-emissivity) glass, be sure to use low-e glass with a visual light transmittance of 72 or higher. Glass with this rating will block harmful light but does not appear tinted.

Aluminum storms are available in several factory colors, or you can paint them a traditional sash color yourself. Avoid the dull mill-finished storms, and finish the storms with a powdercoat or painted finish.