Can wet, commercial, low slope roofing insulation be repaired?

What seems like a very simple, straight forward question can never be that simple when dealing with commercial and industrial roofing.  Can it be dried?  What about the “R” factor?  Will vents get the moisture out or will it make the problem worse?  To get to the bottom of these questions, we need to first consider the problem.​

Once water seeps beneath the surface of a commercial or industrial low slope roof, the water will migrate.  Picture a sponge.  If you pour water over one corner of a sponge over a period of time then the entire sponge will eventually get soaked.  The same will happen to most low slope insulations. The problem is made worse, depending on the type of decking is used beneath the roof.  Tectum deck will allow the water to run straight through, metal deck will slowly drip the water out, and concrete decks can hold back moisture for years before it actually starts appearing inside the building.  Prolonged exposure to moisture in organic insulations (perlite, fiberboard, etc.) will cause irreversible damage.  Just like wood laying on the ground, organic insulations will rot.

Inorganic insulations (fiberglass, ISO, foamglass, etc.) will not decompose like organic ones.  They are closed cell systems that will not absorb moisture and can be dried out with very little damage to the insulation.  Repairing the leak will usually remove the moisture, since typically a negative pressure is present inside buildings, causing the moisture to escape inside the building.​

While your insulation is wet, the “R” value is essentially destroyed.  If you are dealing with an organic insulation, the most common solution is removing and replacing the damaged area.  If the problem is detected early enough, the insulation may be saved by repairing the leak, but if it has progressed to creating a sunken area, it may be too late.​

​One-way vents are very effective for drying out wet insulation.  Usually, one vent for every 100 square feet of surface area is sufficient to dry out wet insulation.