Wood Windows: How to Preserve Architectural Detail While Saving on Energy Bills

Wood has been called a superior building product.  Consequently, even with today's modern materials, wood is still extensively used as a primary building material.  Wood is a readily available, sustainable resource.  It is strong, stable and easy to shape.  Wood has been used to construct window components for hundreds of years.  In fact, until the later part of the 20th century, when aluminum and vinyl windows became available, wood was almost exclusively used in homes to create the light and air giving openings we call windows.

As an old home owner and lover, I believe little detracts from the architecture of a house more than windows that have been replaced with modern windows that do not take into consideration the style, shape and design of the original handcrafted windows.  Most likely, if your home is pre-1900, your windows were finished on-site by a skilled craftsman to fit the openings made by the builder.  Consider for a moment that a well-made window is like a piece of antique furniture.  A skilled carpenter crafted a frame to fit the tight tolerances of the window opening, made tight joints in the narrow pieces of a wood sash and created true divided light with the tiny mullion strips.  Then each piece of glass was individually cut, installed and glazed.  There is a rich history in each window of an old home.

Wood windows, compared to aluminum or vinyl, are easy to repair and maintain with common tools and a little handy-work.  Wood window sashes (the operating window parts) are held in place with four wooden strips called stops.  These stops can be easily removed with a thin pry bar.  Once the stops are removed, the two sashes will lift right out and can be easily worked on at a table or workbench.  With modern glues and epoxies, wood sash components can be tightened, repaired or even rebuilt.  Glass can easily be repaired if broken by removing the glazing that holds the glass in place, purchasing and installing a replacement piece of glass from a local glass shop and re-glazing the glass.  You can even purchase restoration glass that keeps that wavy look not found in modern glass.  Repair is something that is not
possible with modern multi-pane glass.  These glass panels are factory sealed and usually a new sash must be ordered, if possible.  If your kids put a baseball through your window, which glass do you want? Additionally, the vinyl and aluminum components are not easy to repair and usually need to be ordered or even completely replaced.  Wood windows have lasted for well over a century in many homes.  Aluminum and vinyl have yet to prove their longevity.  Aluminum windows have already fallen out of favor because they always feel cold due to the conductivity of the metal.  Vinyl windows are plastic and tend to fade and crack.  Multi-pane glass tends to lose its seal and moisture collects between the panes of glass giving it that fogged look we have all seen.

So why do so many old homes lose their wood windows to replacement windows?  If you take a survey, the most common answer to this question will involve the lack of energy efficiency.  After all, isn't that what we hear on commercials ­ 'save money by replacing those drafty old windows that cost you money.'  Let's examine from where some of the common old window complaints come.

Let's start with the biggest misconception ­ that single pane glass is not very energy efficient.  Most studies of window glass report efficiency in r-value, just like you find in wall insulation.  The higher the number, the better the insulation value.  I found several laboratory studies of window glass on the internet and most seem to agree with the values reported by the U.S. Department of Energy (DOE) studies.  Single pane glass has an r-value of roughly one (add a low emissivity (low-e) film and you can get that to a little over one).  Yes, that is not very high but contrary to popular belief (perpetuated by those commercials again), double pane, insulated glass found in most 'modern' windows only has an r-value of around two.  Add a third pane of glass or a low-e film and you can get an r-value as high as three.  There is not a large difference between all of these when it comes to insulating value.  All glass is a fairly poor insulator!  However, DOE studies show that only about 10% of window heat loss is through the glass.  So where does the heat go?  We need to look at air leaks - think drafty windows!

Old, wooden windows are plagued by one big problem ­ air infiltration.  The energy loss we need to worry about is not due to the window glass but the ability
of the window to seal tightly.  So now we know why we need to replace that old window with a new replacement window right?  Not just yet!  Before you spend
$400-$500 on a replacement window, spend $10-15 and a few hours of your time and fix the drafts yourself.

Weather-stripping is a cheap, efficient way to save a lot of money on those heating and cooling bills. Sealing areas such as the bottom of the lower sash (where the sash meets the sill), the mating rail (where the top and bottom sash meet) and the tracks
(where the sashes slide) you can effectively stop air drafts.  If you stop the drafts, you keep the air inside from becoming like the air outside.  The question is which weather-stripping is best.  If you ask five people, you are likely to get five different
answers.  Some are easy to apply such as adhesive-backed foam (~$5/window) but these do not last more than a few seasons before they need to be replaced.  For a few dollars more, permanently attached products like spring bronze (~$8/window) can provide another lifetime of tight fitting windows.  Take a look at the weather-stripping section of the local hardware store or home improvement center to see all the options available to you.  Many of these products will tightly seal the window sashes in the frame when properly installed.

There is one window item we have not yet discussed - weight pockets.  The weight pockets are narrow, open boxes located inside the walls that contain weights,
usually cast iron, that counter-balance each window sash and keep it open.  The weight pockets in old double hung windows can be a big source of air loss in
your windows.  So how do you solve this problem?  This is a bigger project than weather-stripping but it can be done.  This involves removing interior trim,
accessing the weight pocket, installing a tube (like pvc pipe) for the weights to ride in and finally adding fiberglass insulation around the tube.  An easier fix is to caulk the trim around the window and wall.  This will stop the air from leaving the weight
pocket and create an insulating effect.  Both methods will seal the pocket from air infiltration, stopping drafts, while allowing the window to still operate properly and save money on energy bills.

Finally, if tightening up your windows still does not provide enough of a barrier, consider installing storm windows.  A storm window acts as an initial barrier to air infiltration and produces a dead air space that mimics a double pane of insulated glass.  Storm windows are cheaper than replacement windows and still retain the historic wood windows.  I think most old house lovers would agree that it is always better to cover the original window behind an aluminum storm window than to permanently remove it!  Additionally, consider installing a traditional wood storm window or closable solid shutters on some of your windows.  These provide an historic look that is visible on several older homes around town.

Hopefully, I have demonstrated that it is not necessary to spend hundreds of dollar to replace an old window and lose a large piece of the architectural details of your old home.  You can spend tens of thousands of dollars to replace your windows and may never recover those costs.  For example, assume the average older home has 25 windows.  Assuming it costs about $500 per window, that is roughly a $12,500 replacement cost.  Given this scenario, and assuming savings of $200 in heating bills for four months each year ($800 total a year), it will take you more than 15 years just to break even.  Are you willing to wait that long to recover those expenses in energy savings?  Will it be enough savings to remove all the character old windows provide?  Are you willing to spend a few dollars and your time to tighten your existing windows and save a lot of money for a larger project?  Only you can decide that but I encourage you to consider the points addressed above before you remove any historic windows.

On a related note, please remember where the biggest source of heat loss in your home actually occurs.  DOE studies show that as much as 75% of the heat lost in
your home is through the attic.  Spend your money more wisely and insulate your attic and you will notice increased savings on your energy bills.

Special thanks to the Old House Web (www.oldhouseweb.com) discussion boards for help in writing this article.  There is a wealth of experienced people willing to help with old house issues on this site.  Take a minute to visit if you have questions, or if have experience you would like to share with others.


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