Condensation on the roof sheathing could have several different causes and is difficult to diagnose without viewing the area. A couple possible causes that come to mind, especially this time of year, is due to either air leaks in the attic or a bathroom vent that vents into the attic area. Both conditions would transfer warm, moisture laden air into the attic and upon contact with the colder roof sheathing, this moisture condensates. Solutions would include a full air seal package of the attic area that would address any thermal bypasses and/or ducting the bathroom vent outside of the attic area.

Matt Lang
Greenlight Construction, LLC