Position Statement: Weatherizing Existing Windows
The National Trust for Historic Preservation applauds Congress' and President Barack Obama's efforts to create new green jobs through improving the energy efficiency of homes.
The National Trust is a strong advocate of incentives championed by Representative Peter Welch (D-VT) in Congress' climate change bills that would encourage the retrofit of older and historic buildings. However, preliminary reports suggest a retrofit program with a strong focus on incentives for window replacement. We have substantial concerns about the encouragement of replacement windows for older and historic buildings since windows can be retrofitted for greater efficiency, provide skilled employment opportunities, and are character-defining features of buildings.
It is frequently assumed that window replacement is required to substantially improve the energy efficiency of homes, but existing windows can often be weatherized to achieve efficiencies comparable to new windows. In crafting any legislation to create jobs through home weatherization, Congress and the Obama Administration must consider the important environmental and economic benefits of reusing and improving existing windows.
Consider these facts about weatherizing existing windows:
In Many Homes, Windows Are Often Not the Most Significant Source of Air Infiltration or Loss
- The Department of Energy finds that only 10% of air leakage in homes is attributable to windows. In fact, in the average home, 14% of air escapes through fireplaces – more than through the windows. Upwards of 30% of air infiltrations and leakages occurs through floors, walls, and ceilings. Keeping the fireplace flue tightly shut, installing an inflatable chimney balloon, adding insulation, and caulking to seal air leaks around doors and windows can produce significant improvements in energy performance. [1]
Existing Windows Can Be Weatherized for Substantial Energy Savings
- Studies demonstrate that properly weatherized windows with storm units can reduce heat loss through windows by 50%, a substantial energy savings. Studies also suggest that when windows are properly weatherized and include an exterior or interior storm unit, existing windows can achieve energy savings comparable to or even better than new windows. [2]
Replacement Windows Are Often an Irresponsible Environmental Choice
- The manufacturing of replacement windows – such as those made of aluminum and vinyl – often requires considerable energy and produces toxic byproducts. The environmental impacts of producing these materials must be weighed against efficiency improvements offered by new windows. [3]
- Life cycle assessment studies conducted in the U.K. and Norway indicate that, over a building's life cycle, the overall environmental impact of retrofitting existing windows may be smaller than those associated with the manufacturing of new windows. [4]
- Replacement windows typically fail 10-20 years after installation, and usually after the warranty period has ended. Once replacement windows fail, they cannot be repaired and typically end up in already-overcrowded landfills. New windows are then required, and the wasteful cycle of disposal and replacement continues. Unlike the vast majority of replacement windows, components of historic windows can be repaired, thus extending the life cycle of the entire window unit. Furthermore, historic windows are generally constructed of old growth wood, which is far more durable than modern wood from new growth sources. [5]
Retrofits of Existing Windows Creates More Jobs than New Window Installation
- For every $1 million spent in a construction project, five more jobs are created in the rehabilitation of an existing building compared to new construction. Quite simply, rehabilitation activities are more labor intensive than new construction, in which a significant portion of costs go to materials. The same is true for the rehabilitation and weatherization of existing windows, which requires more investment in labor than materials.
- The labor required to retrofit windows is local. Dollars spent on window repair stay in local economies, creating a more powerful economic stimulus. [6]
Replacement Windows Don't Make Economic Sense
- On average, replacing windows with new, higher-quality replacement windows saves about $50 per month in residential heating or cooling bills. The average window installation costs around $12,000 (the average home has between 24 and 30 windows, replaced at an average of $500-$1,000 each). If a homeowner heats a house six months a year on average, the savings are about $300 a year. At this rate, it would take 40 years to even begin to recoup in energy savings the amount spent on the new windows. Even if a federal subsidy covered half of the cost of window installation, it could still take 20 years for the average homeowner to recover the cost.
- At a time when many Americans are struggling financially, the most economically and environmentally responsible choice is often the weatherization of existing windows, including the installation of a storm window. A more energy- and cost- effective approach is to focus on air sealing and insulation. [7]
[1] U.S. Department of Energy, Energy Saver Tips.
[2] Mattison, DePaola, and Arasteh – What Should I do About My Windows – www.homeenergy.org, July/August 2002; Klems, Joseph H. – Measured Winter Performance of Storm Windows (2002); Wood, Bordass, and Baker – Research into the Thermal Performance of Traditional Windows: Timber Sash Windows.
[3] Thorton – Environmental Impacts of Polyvinyl Chloride Building Materials (2002); Sedovic and Gotthelf – What Replacment Windows Can't Replace: The Real Cost of Removing Historic Windows – APT Bulletin: Journal of Preservation Technology, 36(4):2005.
[4] Asif, Davidson, Muneer – Life Cycle of Window Materials: A Comparative Assessment; Cluver – Still No Substitute – Period Homes, November 2006, Volume 7, Number 6, pp. 12-14.
[5] Cluver – Still No Substitute – Period Homes, November 2006, Volume 7, Number 6, pp. 12-14; Sedovic and Gotthelf – What Replacment Windows Can't Replace: The Real Cost of Removing Historic Windows – APT Bulletin: Journal of Preservation Technology, 36(4):2005.
[6] Rypkema – Economic, Sustainability, and Historic Preservation – Forum Journal 20(2): 2006.
[7] James, Shapiro, Flanders, and Hemenway – Testing the Energy Performance of Wood Windows in Cold Climates (1996); Mahadevan – Domestic Retrofitting Strategies in the UK: Effectiveness Versus Affordability.
