An icy cob house interior

by ziggy on January 17, 2009 -- 6 comments -- Follow

I recently got back from traveling. I have been away for six weeks, so I have not been able to closely monitor the condition of my cob house throughout this very cold Missouri winter.

The night I returned, I went to check out the interior of my house with a flashlight. The outside temperature was something like 1°F or less, and lower with the wind chill. Almost the entire interior of the house was glistening with an icy sheen – the walls, and ceiling all had a light coat of ice. It actually looked quite beautiful but it made me a little concerned. I’m not sure if it’s the result of moisture that is still locked in the house, or from condensation, or what. There is some light mold in some spots, too.

Should I be worried? I’m not sure. Is it enough moisture to cause a problem? I wish I knew. If anyone has had a similar experience, I’d love to hear more.

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  • Just wanted to say that I really enjoy the site. Very inspiring!

  • mountainash

    The caption on the last picture states, “Venting at top of walls was added later to evacuate moisture, an unavoidable condition of bale houses built in climates with extreme weather variations.”

    Thought of this post when I read it and figured I would pass it on.

  • Hi Ziggy,
    I imagine the cob wall still has moisture inside it. I’ve found iciness on areas where the wall was really thin too. I bet it won’t be like that next year. Especially if your keeping it warm inside. Can you keep a window open over the spring? Or warm it up this winter? A little bleach water will take care of the mold. Keep us posted on how it behaves.

    What’s the temp. like inside when it’s 1º outside?


  • Thanks for the comments.

    Mic: Well, there is no heat source in there right now, so it’s about as cold inside as it is outside. I need to pick up a thermometer and stick it in there to see how it compares.

    Occasionally, I’ll open the door and windows to get a draft in there when it’s not TOO-too cold out.

  • Bigham

    It sounds like frosted condensation, which tends to latch on to things like the outside wall of a drinking glass or the inside wall of your home. The interior air in your house is probably full of moisture/humidity from your breathing, and that moisture is condensing and freezing to the outer walls. Just a guess, though.

    I’ve read about a ton of homes and plan to build a dome/hangar style home soon with EPDM… your site will be thoroughly read and I’ll contribute some opinions too. Win Win!!

  • Nicole


    I have just read all of your opinions as what is going on with your Cob structure. It is very important to eliminate any moisture that is circulating around the interior. What happens is it will cause mildew to form on any open pores organic material. It can work it’s way through many layers, especially where the straw cross links or touches another. If you are trying to stay within the lines of “toxic” free, do not keep allowing this condensation to take over your interior structure. You do not want to use “bleach”, Hello? If you are staying totally off the “grid” or “primitive”, go get yourself a wood stove! Plum it in and if you did not reserve a area for this within your walls, best do it while it is still not fully cured. I would be so sad after all your hard work just to find yourself in a structure that is not”sound”!
    I grew up in a Cob brick home in Santa Cruz that my Polish family made by hand. My grandfather created a Cob mud that is stronger and mildew resistant out of all natural materials. He grew up in a 1500’s Cob home in Poland that is still standing in all it’s glory today. In our home in Cali. We had a wood heating system that was feed from the bottom which was below ground. It was circular and ran through all 4 levels of the home. It radiated heat on every level. The stair case wrapped around it from level to level. It was a mixture of Cob and stone. The home was not circular, it had 15ft ceilings and was shaped like a salt box. The corners were not 45~ angles. They were rounded. It is fascinating on how warm it was.
    Good luck Ziggy and please put heat in there soon.

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