Reduce Your Home’s Indoor Humidity… With Plants?

by ziggy on May 25, 2010 -- 7 comments -- Follow

Can this plant lower indoor humidity levels?

April and I have been doing research about how to lower the indoor humidity levels in the house. Recently, the outdoor temperatures skyrocketed to the mid-80s after several weeks of 60 degree temperatures, so everything is really humid and damp… Including the house.

So humid, in fact, that mold started to develop all over the earthen floor, especially around the rugs. We took all the rugs out and I mopped the floor with water, but that was a bad choice… since it didn’t dry easily. A couple days ago, we wiped the floor with vinegar to help kill the mold, and set up a box fan to blow air over the floor (thanks to our neighbors for lending us electricity!) to help it really dry out.

We borrowed a digital thermometer and humidity reader thingy, and it read humidity levels of around 80% inside the house! Hopefully it wasn’t totally accurate… But nevertheless, it’s clear we need to rectify this humidity situation. We definitely don’t want a moldy living environment.

Since we don’t have electricity to run a dehumidifier, April has been researching ways to decrease indoor humidity levels through other means. There’s big silica gel bags that you can hang up to soak up moisture from the air, and then heat up/bake later to dry them out to reuse… But who wants big bags of weird silica gel hanging in their house? We might have to do it if the humidity stays constant, but I thought this was the most interesting possibility….

Air plants – can they reduce indoor humidity?

Air plants! Huh? Plants of the genus tillandsia grow in tropical regions and thrive without soil or root systems – they gather moisture and nutrients from the air itself.

All moisture and nutrients required by the plant is absorbed directly through the leaves by means of the tiny silver scales which cover the plant. The thin walls of these scales permit water to enter the leaves, but prevent its escape. The silvery colour of the scales also helps the plant remain cool by reflecting a portion of the sunlight that reaches the plant…. As you might expect, a plant that is able to cling to the top of a tree, and supply its needs from rain and dust is quite easy to take care of. If they are placed where they will receive bright filtered sunlight and normal room temperatures tillandsias demand very little else. Their need for water can be supplied by either frequent misting, or for those who cannot remember to mist a plant every few days, the entire plant can simply be immersed in room-temperature water for about half an hour every week to ten days. This will permit the plant to absorb all the moisture it will require for the next week or so.

Check out more about tillandsia here. Presumably, if you place the air plant in a humid or moist environment, such as in a bathroom or near a kitchen sink, you don’t even have to worry about misting the plant. Is is then safe to assume that if your whole house is humid that the plant will thrive by capturing some of that moisture from the air, and in effect, lowering your home’s humidity levels? Maybe… but we are so intrigued by the possibility that we just purchased a dozen tillandsia.

Hopefully these plants will help to keep the house drier. If not, it’s still an interesting experiment…

Do you have any ideas about how to passively lower indoor humidity levels? If so, let me know!

p.s. For those that do have electricity, you can read dehumidifier reviews to find the best options available.

Image credit: HK James Ho

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Eva May 26, 2010 at 8:23 am

Salt, put out bowls of salt, large and shallow preferable, the salt sucks the moisture out of the air. You can dry it out in the oven or probably the microwave though I haven’t tried that.

Penn May 26, 2010 at 11:08 pm

It’s really difficult to lower the humidity appreciably in a situation like this because so much water comes in with the warm, humid air from outside. Since you’re relying on natural ventilation, you constantly have humid air coming in. Heating your house up above the dewpoint would lower the relative humidity in the house and stop the condensation on your floor, but that means heating the inside to something close to outside temperature, which defeats the purpose of a high-heat-capacity (or high thermal mass, if you prefer that term) house in summer.

Your tillandsia will probably grow well, but I wouldn’t expect them to make a noticeable dent in the moisture problem unless you pack the entire house with them. A dessicant like the bags of silica will get you farther, but to really solve the problem you need to remove moisture from the air at the entry point into the house. I won’t say it’s impossible, but it will be mighty hard to do without electricity to run either a blower+rotary dessicant system or a standard dehumidifier.

catastrophegirl May 27, 2010 at 2:43 am

lime? basically a lime whitewash will absorb moisture from the air and hold it until the air is dryer, at which point it will release the moisture. i only know the theory though, not the math, so it may not be enough

Theresa June 3, 2010 at 10:58 am

Here might be a solution:

http://heartwoodhomesteads.wordpress.com/2009/12/06/ellies-earthen-floor-in-the-humid-subtropics/

Also, it might help to have air movement, even if it is humid. I saw pictures of a house where he designed inlets at the bottom and outlets near the roof at the north end where it was cooler outside.

Good luck!

Josh in Iowa June 23, 2010 at 2:40 am

As much as I admire your efforts to live with drastically reduced energy needs, I have recently become fascinated by the idea of those atmospheric water generators. Dehumidify the house and drink clean, free water at the same time! Obviously cost-prohibitive, but I still really like the idea.

John C September 18, 2010 at 12:56 pm

Quicklime. A natural antibacterial / antifungal. Try a light limewash if there is no oil in the floor to block it’s penetration.

John C September 18, 2010 at 12:58 pm

I really think a vent up by the skylight would help too. The ceiling is capped with a barrier, holding in the moisture.

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