Why Are There Double-Hung Windows?

By Scott Sidler October 9, 2014

This week’s Ask The Craftsman question comes from Jeremy.

“Why on earth are there DOUBLE hung windows? Everyone just raises the lower sash, but I have a hunch that there may be a reason.”
double hung window
Image Copyright: Scott Sidler

Jeremy, great question and there is most definitely a reason!

A single-hung window is one where the top sash is fixed and only the bottom sash will move up and down. While there are many of these around there are more double-hung windows in which both sashes can move up and down.

Why Double-Hung Windows Are More Efficient

The cost to make a double-hung window is only slightly more than its single-hung cousin due to the additional weights, pulleys and ropes, but the benefits (especially in the days before air conditioning) are incredible.

If you open both sashes of a double-hung window halfway it allows for exponentially more air flow than a single-hung window. The opening above the top sash allows stale, hot air to escape while the opening below the lower sash draws in cooler, fresh air.

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In the days before mechanical cooling people wanted as much cool air and breeze as they could get and nothing was more efficient at cooling down a house than opening a bunch of double-hung windows.

It’s simple science. Think of pouring liquid out of a can or bottle. The liquid comes out in gulps in order to allow air in to replace the space the liquid previously occupied. If you cut a secondary hole in the can the liquid will pour out twice as fast since the liquid isn’t impeded by air trying to get back into the bottle.

There was a method to what the old craftsman did centuries ago and more often than not the design of old windows was based more on basic principles of physics and science than the windows of today.

 

8 thoughts on “Why Are There Double-Hung Windows?”

  1. I extremely LOVE this blog!!

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  2. Scott – My windows date from before 1870 and have no weights/pulleys. Some still have little sash stays that operate by swiveling to press against the frame. I’ll be restoring them this summer and wonder about the upper sashes. Where the lower sashes are missing the stays, I’m adding replacements, but I can’t put those on the face of the upper sash frame or it will interfere with the lower sash movement.

    The upper sashes definitely move (in fact there are great big nails hammered in to hold most of them up *cringe* but what kind of hardware should I be looking to replace those giant old nails with and give me the ability to control the position of the upper sash? Thanks!

    1. Jessica, you could use a spring bolt to hold the window at various positions. They are still available at SRShardware.com. That would likely be my best suggestion for the upper sash.

  3. Great article. My friend send me link of this blog as i am planning to replace my single hung windows in upstairs rooms . I have already received a quote from Landmark home solutions in Toronto. one of the major reasons why i decided to switch to double hung is because it is much easier to clean.I don’t have to hire a cleaning service once i change to double hung windows.

  4. Just bought a 100 yr old craftsman house in southern california, in pretty good shape, but I am going to need your blog to remedy a few things haha. So, I have double hung windows, I think, I only assume because I opened up the casement? and saw 2 rope weights, (well, 4, for each window) but my upper windows have little decorative ‘holders’ or stoppers, look like corbels, keeping that upper one from being operable. I am going to guess someone along the way didn’t want them moving?, why else would there be a set of rope/weights for that window? there are no little handles/pulls for that upper, only my lower. Think I can get them working?? I can send pics if you want to look. Thanks!

    1. Craig, those decorative corbels may actually be a part of the upper sash and it may still be moveable. The upper sash rarely has any handles. If there are ropes and pulleys then I’m sure you can get them working again! Have at it!

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