Keeping a healthy crawlspace is very important.  One of the questions we are most commonly asked is should we close our vents in the summer time or in the winter time? The answer is you need to open your vents in the summer time and close them in the winter. In the summer hot air and humidity build up underneath your home and it needs a place to go. Opening your vents in the summer times allows for your crawlspace to vent properly. If a crawlspace is not ventilated well in the summer time condensation starts to form in the crawlspace. Condensation can form along your joist in the crawlspace, in your insulation and along your floors. This is not good for multiple reasons. Wet insulation isnt as effect as dry insulation as well the extra weight from the water build up can make the insulation hang. Also when humidity and water start to form on joist it can become a breeding ground for black mold and various fungi such as white rot. Also having wet soil in your crawlspace can be condusive conditions for termites. Keeping your vents closed in the winter time traps in heat and helps your home with being more energy efficient. Its also a good way to prevent pipes from freezing during extreme cold. So in conclusion we recommend closing your vents in the winter time and opening them in the summer time.