If you’ve ever spent time in a library or art museum on a hot summer day, you might have felt way colder than you expected. On this episode of Possibly we break down the science of why libraries get so cold in the summer.
Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
Today we have a question from my friend Jen Kennedy. She’s a librarian at one of Brown University’s libraries, known casually as “The Rock.” And Jen has been struggling with a confusing problem ever since she started working there-
Jen Kennedy: It’s freezing in the Rock, especially in the summer when it’s hot outside. I have extra socks, I have gloves, sometimes I even wear a hat. We all want to know, why is it so cold?
So we turned to Nat Hardy and Will Malloy from our Possibly Team to look into this.
Nat Hardy: Hi, Megan!
Will Malloy: Hello!
Megan Hall: Okay so what’s going on here? Why would a library be colder in the summer when it’s hot outside? That seems like a waste of energy, right?
Nat Hardy: It’s a great question, and Jen is not alone on this! The internet is filled with people complaining that their local library is too cold in the summer.
Will Malloy: And the answer is a little counterintuitive! It all has to do with humidity and energy efficiency!
Megan Hall: Are you about to tell me that blasting the AC is actually an energy-efficient solution?
Nat Hardy: Believe it or not, yes! One thing that makes heating and cooling libraries tricky is that the humidity of these spaces really matter.
Will Malloy: Books need to be kept in pretty dry conditions, or else water in the air can damage them.
Nat Hardy: The same thing is true for anywhere that holds sensitive objects, like art museums, or science laboratories.
Will Malloy: To understand how these buildings manage that humidity, we talked to someone who thinks about heating and cooling buildings efficiently, every single day.
Dave Larson: Hi, I’m Dave Larson. I’m the energy engineer in the Office of Sustainability and Resiliency at Brown University.
Nat Hardy: To understand this problem, let’s go back to some of the stuff you probably learned in high school about how humidity works.
Will Malloy: You may remember that the hotter air is, the more water it can hold.
Dave Larson: If it’s 100 degrees out, you can put quite a bit of moisture in that air, and it’ll be fine. Problem is, if you cool that air down, as the temperature drops, its ability to hold that water goes down.
Megan Hall: So the space to hold water is shrinking, but the water isn’t going away?
Will Malloy: Exactly.
Megan Hall: And what happens if the air can’t hold any more of that water?
Will Malloy: It has to go somewhere! So that’s when you get precipitation!
Dave Larson: So it’s going to rain, or you’re going to have fog or snow or something like that.
Nat Hardy: Okay, so now picture this, libraries, like all buildings, have ventilation, which means air from outside gets brought into the building.
Will Malloy: And on a humid summer day, that air from the outside brings a ton of water into the building – way more than is safe for the books.
Nat Hardy: So to deal with this, libraries need to remove that moisture from the air.
Dave Larson: The best way to do that is really to get the air so cold, that the moisture precipitates out of it.
Will Malloy: To do this they use a big system that’s basically an industrial air conditioner.
Nat Hardy: It takes in the humid air from outside and makes it really cold.
Will Malloy: So cold that the air runs out of room to hold water, and the water condenses into a liquid.
Nat Hardy: Have you ever seen a drip of water coming out of your air conditioner? That’s the condensation coming out of the air!
Megan Hall: Cool! So they’ve pulled that humidity out of the air, and now it’s safe for the books?
Nat Hardy: Yeah! Now they have much drier air, but it’s really cold.
Dave Larson: The temperature might be 52, 54 degrees, because you’re trying to wring out the moisture.
Will Malloy: Which is why Jen has to wear gloves in July. The hotter and more humid the summer air is, the colder they have to make it to dry it out.
Nat Hardy: In theory, you could heat the air back up, now that the moisture is gone. And some buildings that want to be really precise about their temperature might do that.
Will Malloy: But that’s expensive, and not very efficient. Think about how high your utility bill would be if you ran your AC and your heater at the same time!
Nat Hardy: So if you go to a library or an art museum in the summer, especially on a humid day, you might want to bring a sweater.
Megan Hall: Got it! Thanks Nat and Will
That’s it for today. You can find more information, or ask a question about the way your choices affect our planet, at askpossibly.org. You can also subscribe to Possibly wherever you get your podcasts or follow us Instagram, Facebook, LinkedIn or X at “askpossibly”
Possibly is a co-production of Brown University’s Institute for Environment and Society, Brown’s Climate Solutions Initiative, and The Public’s Radio.
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