All About Historic Windows

By Scott Sidler • October 22, 2011

4 pane casement window

For me, windows are one of my favorite, and at times, most challenging  (they’re one of the few parts of a house with lots of moving pieces!) aspects of a classic home. Windows truly are the eyes of your home and I have seen too many homes with a black-eyes over the years. A home and its occupants look out onto the world through these sometimes simple, sometimes complex contraptions to keep out the elements and let in the light. And the world learns a lot about your home by its windows.

A Brief History

In the first homes, windows were more than a decorative way to light the room. Originally, there was no glass, simply a crude opening designed to let fresh air in, smoke from the family’s fire out, and light the space. This lack of glass was the reason for the first shutters. After all, you didn’t want a hole in your wall during a rainstorm or a brutally cold winter, not to mention all the bugs. Eventually, glass came into the picture. First for the rich and the nobility and then slowly to rest of the masses.

Up until 1900, all glass was handblown and large pieces were very expensive. The expense and relative unavailability of large pieces of glass resulted in windows with several “lights” (meaning individual panes of glass) being the trademark of the days. In 1900 a new technique was invented and the predecessor to modern glass, called machine-drawn glass, was born. Hand-blown glass was mainly good for letting light into the room as the images seen through the glass were usually a blurry mess. Machine-drawn glass greatly improved the clarity and consistency of glass but was still far from perfect. As glass making skills increased, the size of individual panes increased as well resulting in new combinations such as 6-over-6, 4-over-4, 3-over-1, 2-over-1 and eventually glaziers could construct a window out of a single pane of glass.

Windows are typically described by their number of panes (6-over-6 has an upper sash with 6 panes and lower sash with 6 panes) and by the way they open (ie. double-hung has 2 sashes the open independently of each other whereas a casement window swings in or out on hinges).

9 over 9 double hung windows

In 1959 modern glass, which is the type still used today, was invented and glass could be had in almost any size with a uniform thickness and flawless clarity. But those of us who like the special “glimmer glass” in our old homes that was the day windows with character began to die.

What Kind Do I Need?

Today you can buy windows in more forms than our forefathers could have imagined. Double, triple, even quadruple-paned windows filled with inert gasses like argon to prevent heat or cold transfer. They have become an efficient part of the house, yes, but when dealing with a classic home from generations past, an out-of-place window from the wrong time period can destroy a beautiful facade. Windows of yesteryear each had a purpose and served a function. For example, double-hung windows were designed with an upper and lower sash that could be opened independently of each other. The top sash (which on most older homes has been painted shut over the years) was designed so that in the days before air-conditioning, warm air could escape from the house and be replaced by cool air entering from the bottom sash.

The anatomy of a window (courtesy Old-House Journal)

Pre-war windows were also glazed with linseed oil putty to make the panes airtight. Caulking may last for years, but it doesn’t come close to the 80 year life span of properly cared for glazing putty. Also, being made from old-growth timber, original windows are surprisingly rot-resistant. I’ve had to completely rebuild only 2 windows out of the 32 on our 1929 bungalow, and those 2 were the only non-original windows in the house! The 2 replacements were a mere 20 years old before they succumbed to the elements!

So, before you decide to replace your drafty old windows, stop and think. They can be restored to their original appearance, working condition, and efficiency with period weather stripping (copper not foam or rubber.)

If you’re not sure about whether your windows are candidates to be saved, visit our resource page on How To Restore Old Windows

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83 thoughts on “All About Historic Windows”

  1. We recently cleaned out the old barn on the property and we found some very large 4 pane glass, wooden frame windows. They all have 3 roughly 2″ circles in the wooden frame and a piece of wood that slides up and down to cover and uncover them…. has anyone seen this before or does anyone know what it was for?

  2. Is the weather stripping the vertical metal pieces the sash travels on? I’m needing to do some work on my c. 1930 windows and I cannot figure out how to get the sash off without destroying that metal piece. Tips or tricks?

    1. Its a little bit of a tricky process I spell out the steps in my book Old Windows In-Depth available in my store. If it was simple I’d be happy to share but it takes lots of pages and lots of pictures, but the long and short is that you have to remove the weatherstripping with the sash and reinstall it with the sash when the restoration is complete.

    2. Megan… What you describe are likely storm windows typically installed over the permanent windows (generally double hungs) during the cold weather months. The 3 holes were there to allow for ventilation on warm days (simply pivot the closure piece up to ventilate and then down to close it off).

  3. I have always been convinced of the value of older windows. My present home, circa 1915, has many 28×72 double hung (with weights) windows. I have restored all of them, BUT the previous owner replaced 12 of them with cheap aluminum products. Does anyone have an idea where I can find used windows (6 panes per window) of the above dimensions?

    Condition is not important; I am equipped to replace damaged wooden parts.
    I live in Central Texas and will travel to your location.

  4. Hey
    Just wondering if you know the meaning of the small colored panels of glass around a larger window mean. I was told if you held a candle to a certain color it would pass a message to the neighbors. Like for example if it was safe etc.

  5. I am considering buying a 1940s Tudor with original casement windows. I hate to change them, but definitely want to be able to have “normal” windows that open, have screens, and are good insulation in the cold Pennsylvania winters. Is it possible to replace the old with new windows that respect the look of the originals?

    1. Why replace them when you can restore and weatherstrip them? Adding a storm window will get you the same energy efficiency as a new window at half the cost and keep the historic character.

  6. Do you know why some older brownstone buildings have double hung windows between interior rooms?

  7. I have an old window, Sears Chicago bungalow, that is kept open by an attached pin on the lower window which slides into a plate on the upper window to keep it open. I need to replace that plate, but have no idea what it is called. Can anyone help?

  8. Due to lead based paint remediation over 20 windows have to be replaced for my client’s historic multi-family property located in an established historic district. This will cause a devastating financial hardship.

    Are there grants for non-owner occupied historic home window replacements in NJ?

    Does any window vendor offer a promotion for this?

    Please advice and thank you!

    1. We just had our lead-painted windows stripped and repainted. It took a while, but the cost was competitive with replacing them with new vinyl windows, and they will last much longer. There are many window restorers in the area (we’re in Philadelphia).

      1. Anyone in particular you would recommend? I’m in Ardmore. And do you have any idea what type of wood was commonly used? My window wood looks like cedar but smells like an ailanthus tree when I sand it. House dates to 1880’s. Any ideas?

  9. Hi…I found some old windows from a cottage up North. They are wood frames and the kitchen windows have 3 small holes at the bottom with a wood lever on the inside as to open or close off the holes. Just wondering if this would have been to let air in or what? Thanks

  10. Our organization has a 1906 Kremmling (CO) Depot created on the Moffat Road railroad rout. It has 2 styles of windows. One is a 2 over 2 style, the other is 3 over 2. Could you tell me if these are from different years? If so, which ones? Thanks so much!!

  11. I have an old sash style screen frame for my kitchen window that I am sanding to repaint. I removed the little handles to make this job easier. There also was a strip that was screwed onto the top outside edge that I thought was a strip of wood but found it to be a piece of metal that is flat on the backside and rounded on the front or outside. Can anyone tell me what or why this was on there and if it’s necessary to put it back on once I have it all repainted ? This window is original to the house that was built in 1952. It gets set into place under a widow frame the same size above it. Thank you in advance for any help you could send my way, Scott

  12. Have 1820 white Brick Farmhouse…3 bay with center front door with transom. Want to replace vinyl windows with original style but not sure of how many lights: 2 over 2, 4 over 4, of 6 over 6?? Read that 2 over 2 started 1880’s but don’t know what would look good.. Checking out Marvin windows but husband said he might make them. He is very talented! Just not sure what color to paint sashes.

    1. Jo – I have an 1825 twin chimneys colonial farmhouse. Went to a workshop on old home restoration and learned that this era homes would have had 6 over 6 windows. Mine have been replaced with 2 over 2s. Would love to restore back to 6 over 6s, but dreading that little chunk of change – many windows. Good luck!

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