The Value of Original Window Repair and Retrofit: Studies and ResearchThe issue of the retention of original windows in preservation, and lately, in sustainability, is so high profile that it merits its own web page. It is commonly asked where the arguments are to defend original windows, and how to answer the proponents of window replacement. The perception of preservationists is that there is a large replacement window industry advertising the attractiveness, the “no maintenance”, and the energy efficiency of a new window, but no one to promote the attractiveness and energy efficiency of a properly maintained original window. Occasional maintenance is required of a historic window; they were built to be reasonably maintained by the owner of the building. New windows are “no maintenance” because when they break, they have to be replaced. Maintenance is not possible for a modern window.
Lately, new pressure to replace windows is felt from the “green products” and third party energy certification industries, which emphasize the energy efficiency of new windows and encourage their installation. To their credit, third party certifiers are beginning to acknowledge that repaired windows have equal value to replacement windows in their point rating systems.
Many studies demonstrate the viability of repairing original windows. Some of them are collected here. All of the studies conclude that original window repair and other conservation strategies provide similar energy benefits of a replacement window, with less impact to the environment as an existing resource.
“Improving the thermal performance of traditional windows” by Paul Baker for Historic Scotland.
“Replacement Windows and Furnaces in the Heartland: Indiana’s Energy Conservation Financial Assistance Program” by William H. Hill. This is the 1990 study that demonstrates a four hundred year payback using replacement windows.
“Measured Winter Performance of Storm Windows” by J. H. Klems. This Berkeley storm window research focuses on north-facing storm windows using low e glazing. It uses rigorous scientific analysis to conclude that no difference is found in performance between the low-e storm with an original window and a low-e replacement window.
“Building Regulations and Historic Buildings: balancing the needs for energy conservation with those of building conservation” The English Heritage Interim Guidance article touches on all parts of preservation and conservation of power and fuel, and the chapter on windows is very relevant.
“Repair or Replace Windows in Historic Buildings: Arriving at a Sustainable Solution” The Heritage Canada file contains two articles, one from Andrew Powter and Craig Sims discussing how to arrive at a decision to replace or repair original windows, and Susan Turner explains the sustainable nature of window repair rather than replacement.
“Life Cycle Of Window Materials - A Comparative Assessment” by Asif, Davidson and Muneer. A comparative life cycle assessment of the environmental impact of different window materials is included for its interesting materials energy cost analysis.
“Domestic Retrofitting Strategies in the UK: Effectiveness vs. Affordability” is an interesting presentation of the effectiveness of different energy retrofitting strategies, including shutters.
“What Replacement Windows Can’t Replace: The Real Cost of Replacing Historic Windows” Walter Sedovic and Jill Gotthelf provide an excellent discussion of the comparative value of window replacement versus repair. Many aspects of sustainability are considered.
“Testing the energy performance of wood windows in Cold Climates” by Brad James, Andrew Shapiro, Steve Flanders and Dr. David Hemenway is a thoroughly researched paper that concludes that historic windows should not be replaced for energy considerations alone, as retrofitted and replacement windows perform similarly.
“Lincoln Hall Windows Research Report: A Case Study of Options for Treatment for Windows at Lincoln Hall, University Of Illinois, Urbana Champaign” This report provides empirical data to assess window repair or replacement options for a proposed LEED Gold project, addressing the existing windows in terms of energy consumption.
A windows tip sheet is included from the National Trust for Historic Preservation to provide good basic guidance and vocabulary.
