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Window Know-How; Preservation Nation

March 9th, 2009 · 4 Comments

A Guide to Going Green

To live green at home, and reduce your monthly energy bills, it’s important to evaluate windows. If you live in an older residence, don’t assume that replacement windows are the only option. Historic wooden windows are remarkably efficient as long as they’re well maintained. (And there’s nothing greener than preserving what you already have.) Conversely, manufacturing and installing replacement windows consumes enormous amounts of energy. Keep these tips in mind as you consider your options:

Older is Better:  Old windows were fabricated from old wood. It’s generally denser and lasts longer than the new wood used for modern windows.

Caveat Emptor: Some salespeople promote replacements as cure-alls, but even the highest-quality replacement units can fail. In addition, experts note that new vinyl or PVC replacement windows can release toxic byproducts into the atmosphere.

Watch Your Pennies: Tearing out existing windows to install replacements is expensive and wasteful.Although you may achieve some energy savings, it will take decades (or centuries) to recoup your investment. Plus, you’ll have to dispose of the old windows, adding to the nation’s waste management woes.

Maintenance is Key:  A well-sealed, tight-fitting window saves energy.

Check for Condensation: It can rot window sills and rails.

Use Storm Windows:  They increase energy efficiency. Monitor them for clues about your house. Cold air leaking in through a storm window can create condensation on your window panes. Warm air escaping from your house can cause a storm to fog up.

Insulate:  More heat is typically lost through the roof and walls than through windows. Adding just 31⁄2 inches of insulation to your attic can save more energy than new windows.

Install Window Treatments:  Something as simple as a conventional window shade mounted inside the frame and touching the sill, with no more than a 1⁄4-inch gap at the sides, can reduce heat loss by as much as 27 percent. A shade with a reflective coating will provide even more protection.

Remember to. . .
1.   Keep all exterior surfaces painted  A coat of paint protects wood. Pay particular attention to horizontal surfaces, such as window sills, where water collects.

2.   Replace glazing compound (the putty that holds panes in place) when it dries out. Missing or cracked compound results in air infiltration. Always paint glazing after it has cured.

3.  Maintain window locks Functioning locks hold rails tightly in place. A tight fit reduces air exchange.

4.  Keep movable surfaces free of paint buildup so that sashes slide freely.

5.  Replace any cracked or broken panes promptly.

6.  Add or renew weather stripping where it makes sense.  When correctly installed, weather stripping can increase a window’s efficiency by as much as 50 percent.

7.  Watch for water  Whenever you use storm windows, remember to clear the weep holes at the base to allow condensation to drain away.

8.  Check seals around exterior storms and caulk well.

9.  Test for air leaks On a windy day, hold a lighted birthday candle or incense stick near the window frame to detect drafts.

10.  Think about safety  Evaluate emergency exit routes before sealing windows with caulk or  adding storms.

Sum of Its Parts
A. Jamb
  Vertical or horizontal member that frames the window opening

B. Rail  Horizontal part of sash

C. Pane or Light  Glass held in place by glazing putty and metal glazing points

D. Top Sash  Upper section of window, may slide down to open

E. Stile  Vertical part of sash

F. Meeting Rail  One of the two horizontal members of a double-hung sash which come together

G. Muntin Strip that separates the panes of a window. The shape, or profile, of a muntin provides a clue to the window’s age.

H. Bottom Sash  Lower section of window, typically slides up to open

I. Casing  The finished, often decora­tive, framework around a window

J. Stool  Interior shelf-like board at the bottom of a window against which the bottom rail of the sash rests

Window Know-How Illustration
(Illustration  by mckibillo)

Sources: Forum Journal, 20, no. 2 (2006), National Trust for Historic Preservation; Historic Home Works, historichomeworks.com, calculations by Keith Heberem; Cornell Extension Service

Tags: Value-Added Historic Preservation · windows

4 responses so far ↓

  • 1 John Leeke // Mar 10, 2009 at 8:42 am

    Thanks for listing Historic HomeWorks as a source.

    >>Install Window Treatments: Something as simple as a conventional window shade mounted inside the frame and touching the sill, with no more than a 1⁄4-inch gap at the sides, can reduce heat loss by as much as 27 percent. A shade with a reflective coating will provide even more protection.<<

    I know this is true from my own experience and it’s fascinating to have the facts on it. What is your source for this info?


  • 2 ron // Mar 10, 2009 at 7:11 pm

    Hi John,
    I uploaded the article from the latest Preservation Nation Emagazine.
    Even though Amy and I are now selling Green Mountain Windows in addition to our restoration work, I am still trying to battle the industry sales pitch about “efficiency” vs historic preservation. So I collect all the literature I can and try and make our website like a “Utne Reader” for the local preservation folks.

  • 3 Holly Brunk // Sep 14, 2009 at 3:14 pm

    I own a home built in 1870 with original windows. Most are sash, a few are of unique construction and function. The windows are loose and leaky. Some of the glass and muntin strips are thinner than current standards, the wood is in good shape. Would you recommend restoring the windows for tighter fit or having custom storms built? I am most concerned about energy efficiency and preservation of original features.

  • 4 Ron Wanamaker // Sep 14, 2009 at 8:08 pm

    Hi Holly,
    Thanks for the question. It sounds like you might have some pretty beautiful windows in your house. It IS difficult to replace those thin muntins and even more difficult to replicate that old wavy glass.
    All that being said I think you are on the right path. Both approaches would be warranted in an historic house. According to the EPA and other independent testing agencies single pane windows with a good fitting storm window perform as well as double insulated glass. Amy has recommended that people start with a good traditional wood storm window and then approach the “restoration” one sash at a time. So I guess both, starting with a storm.
    Now in full disclosure we sell Green Mountain Windows and they make a wooden storm window out of cedar with a removable glass panel so that they operate as a screen window in the short Vermont summers. But any quality storm window would improve your energy efficiency and help retain the benefits of your historic windows. Not enough is made of the economic benefits of original windows in historic homes. In South Carolina the state did a study that found that historic buildings with their original windows sold for an average of 14% higher than homes without their original windows.
    Once you improve the thermal efficiency of your storms then you have the time to slowly improve each window one or two at a time for the longest term benefit.

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