Windows

The most common types of windows are double hung, single hung, awning, casement and sliding, decorative, storefront, and leaded/stained glass. Contrary to popular belief, old and historic windows are generally more energy efficient than one might believe. It is important to look at how much energy is consumed in the making of the window as well as the lifespan. Generally speaking, historic windows used less energy to be manufactured and were built as though they would always be a part of the home. Modern windows use far more energy and produce much more waste during production. They also have life spans of only 10-20 years. Remember that historic windows were built to be naturally energy efficient and help circulate the air within a home. Before you buy new windows, look at all of your options. Historic windows can be retrofitted to fit today’s energy specifications and small repairs on an existing window will save you both time and money in the long run. The Dallas Window Survey Form will help determine what changes need to be made to your windows.

Recommended: Always complete a Dallas window survey before doing any work. Identifying, retaining, and preserving windows and their functional and decorative features is important in defining the overall historic character of a building. It is vital to conduct an in-depth survey of the condition of the existing windows early in rehabilitation planning. Once this is complete repairs and upgrading methods and possible replacement options can be fully explored.

Not Recommended: It is not recommended that you remove or radically change windows, which are important in defining the historic character of the building, so that the character is compromised. Please do not strip the windows of any historic material or replace windows only because of peeling paint or broken glass. Windows that are not entirely in different pieces can usually be repaired.

Repair vs. Replace: Generally, if a historic window has been taken care of, it will never need to be replaced. Removing the existing windows not only compromises the appearance of your property but it can also reduce its value, as well as how much you save in property taxes. Replacing a window should be considered if the window is missing, or if it cannot be repaired. Replacement should never be the first option!
 

Window Tier System

Tier One windows are classified as those which are visible from the street. They may be replaced if the original windows are missing or are in poor condition. If replaced, the new windows must be compatible with the original ones, and the overall character of the home and the district should not be compromised. This can be easily achieved by making sure the existing windows match in profile as well as dimension to the originals. If it is not possible that the window is made of the same material, try to use a highly compatible material or finish. It is also important to maintain the original method of operation for the window. However, in some cases, single hung windows may be substituted for double hung windows.

Any window not falling under Tier One will fall under Tier Two. These are not as critical to maintaining character, however they should be preserved if possible. The one exception to the rule is any Tier Two Window that has no street visibility. Tier Two uses the same guidelines as Tier One, except they tend to be a little more lenient.

Thermal Efficiency Improvements: Basic improvements for energy efficiency are often very obvious. The addition of interior blinds, an exterior awning, or even shade trees are all things that can cut down on your heating and cooling bill while still maintaining the existing integrity of the property.

Possible Solutions: Consider adding caulk between exterior window jambs and the surrounding wall surfaces and installing weather stripping. There are many window film products on the market currently that can be added to historic glass to cut down on heat gain. Another common solution is to replace the old glass with a dual-pane. This works best with wood windows because of the sash thickness, but can also work with steel windows.
 

Common Questions (answered in supplemental articles below)

1. Aren’t new windows more energy efficient than old ones?
2. If I have to replace a window on a historic property, can I use a vinyl one?
3. Where can I find a reputable salvaged materials seller in Dallas?
4. How can I cut down on the solar heat gain associated with my windows?
5. What are some other ways to make sure my historic windows remain energy efficient?

Supplemental Articles

NPS Preservation Brief 9 – The Repair of Wooden Windows
NPS Preservation Brief 11 – Rehabilitating Historic Storefronts
NPS Preservation Brief 12 – The Preservation of Pigmented Structural Glass
NPS Preservation Brief 13 – The Repair and Thermal Upgrading of Historic Steel Windows
NPS Preservation Brief 33 – The Preservation and Repair of Historic Stained and Leaded Glass
 

Support Documents and Websites

Dallas Window Survey Form
National Trust for Historic Preservation – Saving Windows Saving Money
Washington D.C. – Windows and Doors for Historic Buildings
City of Phoenix Guide to Window Repair & Replacement (Part 1)
City of Phoenix Guide to Window Repair & Replacement (Part 2)
City of Phoenix Guide to Window Repair & Replacement (Part 3)