Historic Preservation Resources
- National Trust for Historic Preservation (NTHP)
- Office of Historic Preservation (OHP)
- NEW! OHP's Section on Substainability
- California Preservation Foundation
- Secretary of the Interior Standards and Guidelines
Focus on Historic Wood Windows
WHY KEEP ORIGINAL WOOD WINDOWS
By Bob Felter and the Arcata Historic Landmark Committee 2013
Originally the double hung windows in an old house sealed out the weather and glided with an effortless pull of the hand. One hundred years later, they might rattle, be stuck closed, leak air through poor mating and loose joints and be a struggle to open. Add a window salesman’s boasts to cure these ills and save energy, and original windows are disappearing at an alarming rate.
Windows are the “eyes” to the house. Saving original windows preserves the home’s character and adds value to old homes. They reflect the architect’s design intent of the building, and can be examples of exceptional craftsmanship and design. Made of durable and decay resistant old growth wood they’re made of materials that last. Historic glass adds another level of charm. Double hung windows were first invented in the 1400’s as air conditioning systems and are still practical today.
Wood windows are built to be repaired. Any part can be removed and remade. Properly maintained, a window made of old growth wood will last indefinitely. There’s no reason why a 100 year-old window will not last another 100 years. A deteriorated window is a product of neglect and disregard for the building. Generally, if a wood sash is less than 50% deteriorated, it is probably cost effective to rebuild it. If more, a replacement sash made of old growth wood is worth the cost. Of course, maintaining glazing putty is critical in preventing moisture from invading mortise-and-tenon joints where dampness encourages rot. Maintaining the glazing is a relatively simple thing to do.
The first step in improving an old window’s performance is to remove the sash and clean up the parts. In double hung windows, paint drips have often hardened between the “meeting rails”, the horizontal rails where the two sash mate. No matter how hard the sash locks are turned, air creeps through. Another step is to refasten the stops snugly so less air gets past. Sash cords are simple to replace, weights can be rebalanced and other offending blobs of paint can be easily scraped off using a heat gun. While caution and education is recommended, a sash can be easily stripped of lead paint where that is a concern.
A successive step is to weatherstrip the window. Weather stripping improves the ability of an existing window to remain airtight by sealing gaps. There are numerous methods and products available, including vinyl bead, felt or plastic strips, spring metal and compressible foam shapes. This can be done by homeowners with some savvy and the right tools, or professionals. Weatherstripping can be accomplished even more easily, though probably less permanently by homeowners with self stick V-strip vinyl.
Replacement windows are often billed as “maintenance free”. There’s no such thing as maintenance free. Aluminum windows conduct heat and cold so have become obsolete except for commercial applications, so the latest incarnation of such a window is vinyl. Vinyl, a petroleum product, cannot be repaired when damaged, nor painted with any method that will hold up. It is one of the most toxic materials manufactured today, becomes brittle with age, and discolors with time. The first attempts in vinyl window manufacture came in two colors, brown to mix with the then popular “bronze” aluminum windows, and white. The brown color absorbed heat and warped, costing manufacturers large headaches and were quickly eliminated. While white, or almond colors are sold in huge quantities, they still have a questionable lifespan.
Vinyl windows have now been around for about 30 years. No one knows if they’ll last 100, but many of these windows installed since the 1980’s are failing at an alarming rate. Vinyl expands more than twice that of wood, and seven times the rate of glass, which can cause the seal to fail. In addition, vinyl begins to soften at 165 degrees Fahrenheit, a temperature easily reached between a window and drapes. It has been said of such replacement windows, “They call them replacement windows because you replace them over and over again”.
An old wood window, paired with an exterior or interior storm window can easily outperform a new insulated glass unit. A cellular shade can do the same thing. By replacing single glazing with insulated windows, energy savings are seldom realized Depending on which study, the payback on replacement windows is anywhere from 30 to 250 years. Almost every retrofit measure, from weatherstripping, installing storm windows, or cellular shades offers a better return on investment than outright window replacement. Interior surface films are another option that help to some degree.
Storm windows can be built to open, providing ventilation and allowing egress. An exterior storm window will reduce maintenance on the primary window and be simpler to maintain. Interior storm windows can be easier to remove on higher windows. At least one local glass company is specializing in this trade.
If retrofitting glass in an old sash is something you feel must be done, 1⁄4” laminated glass has better UV protection than low-e coatings. It approaches the same thermal capabilities of insulated glass, is more soundproof, is safer and costs less. It may also be possible to laminate historic glass to allow the energy and noise benefits while maintaining an authentic finish. Single pane, low-e glass is also available.
Besides tackling windows, the first intervention a homeowner should take is air sealing floors, walls and ceilings, adding insulation and upgrading the heating systems. Sash weight pockets are much less of a heat loss problem when a house is properly caulked.
Replacing windows is the antithesis of “green”. The embodied energy of old windows is hauled to a landfill, while the manufacture and transport of new units consumes resources. In addition, hiring local labor to improve windows keeps dollars in the local economy rather than sending those dollars to a distant city. Download full report: www.preservationnation.org/saving-windows-saving-money
Bob Felter is a local contractor who is also an extraordinary volunteer at HSSA—making sure our fixes and changes are beautiful and historically accurate.
- OHP, Window Repair and Retrofit: Studies & Research
Of particular interest:
- Improving the thermal performance of traditional windows by Paul Baker for Historic Scotland. (This is a PDF)
- 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
- (PDF format) NTHP's Tip Sheet on Historic Wood Windows