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Building Science

Controlling the Humidity in Your Home During Winter

Hint: Airtight homes usually don’t have a problem with dry air

How's the relative humidity doing in your home this winter? [Photo credit: Energy Vanguard]

I’m going to go out on a limb and make what you may think is an outrageous statement:  Water is the most interesting substance in the world.  Some of you may immediately respond, “Oh, yeah!  What about beer?”  (Or wine, or Sidecars, Negronis, or Sazeracs — or whatever your drink of choice is.)  Without water, we wouldn’t have those drinks.

But what else makes water so interesting?  Well, let me name a few things.  The water molecule is polar, which makes for lots of interesting properties.

 

The water molecule has a positive end and a negative end, resulting in all kinds of interesting behavior. (By Wikipedia User Qwerter at Czech wikipedia: Qwerter. Transferred from cs.wikipedia to Commons by sevela.p. Translated to english by by Michal Maňas (User:snek01). Vectorized by Magasjukur2 - File:3D model hydrogen bonds in water.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14929959)
The water molecule has a positive end and a negative end, resulting in all kinds of interesting behavior. [Image credit: Wikipedia User Qwerter at Czech wikipedia: Qwerter. Transferred from cs.wikipedia to Commons by sevela.p. Translated to English by by Michal Maňas (User:snek01). Vectorized by Magasjukur2.  File name: 3D model hydrogen bonds in water.jpg. Source: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14929959]
When liquid water becomes a solid, it does the opposite of most other materials making that phase change:  It becomes larger!  And did you know that liquid water reaches its highest density at 4°C (39°F), not 0°C (32°F)?  That’s right.  It starts expanding even before it freezes.

That fascinating property ensures that fish don’t freeze into a block of ice in winter — because as the air above chills the water in a lake or pond, the water becomes more dense and sinks, until it reaches 4°C.  As the temperature goes below 4°C, the water becomes less dense and sits on top of the more dense water.  And that’s why lakes freeze from the top down instead of the bottom up, sparing all the fish in the process.

But you’re here to find out…

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4 Comments

  1. User avater
    Nils Bird | | #1

    I've been wondering what kind of feature I could design into my retirement home that would give me an incentive to go outside and not be bothered by boredom and malaise due to too much comfort.

    1. User avater GBA Editor
      Martin Holladay | | #2

      Nils,
      If you live in a rural area, the solution is to include an outhouse and no indoor plumbing. I lived that way for a few years in the 1970s. You get to see the stars, and in winter you'll see the Northern Lights.

      1. User avater
        Nils Bird | | #3

        I did that in the seventies and I have fond memories of the stars and the northern lights. I also had no insulation, no dry wood and an inefficient wood stove. Getting the runs in the middle of winter I remember much less fondly. I am going back to the same place and am thinking of a much less coercive design feature. I used to spend many hours outside with axe and crosscut saw. The wood warmed me once finding and cutting, another time hauling it up hill to the house and the third time in the firebox. Maybe a toned down version of that feature would work.

  2. User avater
    Paul Kuenn | | #4

    Luxury! If you lived by the Great Lakes you'd see we have other issues. For those in the mountains and any terrain above 1,200 Ft above sea level, you do dry out. You can see in my attachment we deal with over 50% humidity outdoors even at -28F.

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