Despite all this, there are also the wood-movement deniers. These people respond saying that they think that given modern climate control wood movement is not the issue it used to be in the past. I’d like to think that I can inform them otherwise with this blog post but I have my doubts.
Modern climate control systems regulate temperature, but do not actively regulate humidity. In fact, they can even exacerbate seasonal humidity changes. The big factor for wood movement is relative humidity, which is the percentage of water in the air relative to the maximum amount of water the air can hold. For example, when the relative humidity reaches 100%, it usually rains.
In the winter, colder weather means there is less water in the air, so when your furnace warms up your house, the relative humidity drops like crazy. This is why all the wood in my house is shrinking. The warm dry air circulating through my house has been pulling the moisture out of my furniture for the last two months. Gaps have appeared in the Adirondack chair I made for my daughter six months ago. Our floors have become extra squeaky, and the poorly laminated legs of our dining room table are literally pulling themselves apart.
In the summer, warmer weather means more water in the air. Even if you don’t live in a part of the country that gets uncomfortably humid, warmer temperatures means the air is is going to hold more moisture than in the winter. The moisture levels in the air and the wood it surrounds really want to be equal, so our furniture pulls moisture out of the air and is happy.