Does cellulose insulation require open windows for venting?
You ideally want your attic to be the same temperature and humidity as the outdoors. By sealing, you almost certainly are making the space warmer and more humid. In hot climates, this could cause your roof to get to hot and reduce the lifespan. In cold climates, the attic could stay or get above freezing, cause melt, and refreeze at the edge causing water dams.