In the past, I have heard not to block the vents unless it is going to be below freezing for a long period of time. I was under the assumption that venting under a foundation, and an attic was just as important in the winter as it is in the summer.
Am I wrong?
Please let me know your thoughts on this.
J.M. in Oregon
You are correct, it is important to keep from building up excessive moisture in the crawl. It is also important to keep the pipes from freezing. This is always a source of confusion when we talk about venting in the cold weather.
In attics, you have the heat rising up from the house meeting with the cold air of the attic, and creating a condition for moisture if not properly vented. This makes the cold months the ones that create the best conditions for having moisture problems in the attic.
The summer months create the best condition for moisture in the crawl space. However, anytime you have two different temperatures getting together you have moisture concerns.
I recommend leaving the crawl space vents open until the temperature gets below freezing. This will keep pipes from freezing. But, make sure to re-open them when the temperature gets above freezing.