Q. My floors are buckling. I was in the middle of putting on an addition when Sandy hit. My crawl space filled with water. I had two inches on the first floor, so I needed to get the wood floors replaced. Our contractor put down oak floors and insulated the crawl space, but now we learn that he put tar paper under the floors, over the old plank subfloor, and left out the vapor barrier in the crawl space. He said he did this so the floor could continue to dry out and breathe. Now the wood is cupped and the air-conditioning people are saying to lower the temperature. What should we do?
A. Funny how one thing done in the wrong order or wrong place can unravel everything else. I wasn’t really looking for the guilty party when I crawled under your house, but I found them. You have a combination of problems. In general, the air in your home and in your crawl space always has moisture in it, even though, at times, the air can be very dry, such as when the heat comes on in the winter. Moisture in the air, in the presence of a temperature difference on surfaces, will create condensation at what’s called the dew point. The reason for the vapor barrier on the face of insulation is so that moisture can be blocked from working its way through the wall, floor, or ceiling that the insulation is up against. Insulation is there to slow down the temperature exchange, not to stop it. On a hot day, when it’s 90 degrees outside and you lower your air conditioning to 70, more droplets will form on the back side of your painted wallboard, inside the wall cavity, where you can’t see it. When it’s 70 indoors and 20 outdoors, you get the same effect.
The floor I looked at did have a vapor barrier in the wrong place. It was supposed to be below the subfloor, not on top of it, and the problem was compounded by the duct installers, who boldly went where no man has gone before and removed insulation to put their duct under the floor. They gave you half an answer, and not even a good answer, by suggesting that you lower the A/C, because the greater the temperature extreme in the presence of humid air, the more condensation. In addition, they contributed to and worsened the problem of the cupping floors, which were mostly in the area where they pulled insulation to install ducts. Whoever did that probably had no idea what they were causing, and also probably thought nobody would crawl under the house to investigate. So, for a short consult, you now know the truth. Next week, the solution.
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