Inadequate Roof Ventilation - Mold and Mildew Problems and Solutions

January 3rd, 2013

One of the keys to the performance of a commercial roof is for the roof system to maintain constant temperature. Buildings in extreme weather conditions will of course experience heat and cold based on the outdoor environment. The question is, how much will those temperatures fluctuate? If there are large swings in temperature over short periods of time, this can cause problems in a roof system.

One of the most important factors to ensure constant temperature in a roof system is adequate ventilation. When roof ventilation is balanced, i.e. the air intake is equal to the air exhaust, the life of the roof itself is prolonged and the environment protected by the roof system is more easily optimized. When the roof doesn’t have proper ventilation any number of problems can result.

Mold and Mildew

In very humid climates one of the most common problems which can occur underneath the roof deck is mold and mildew. Temperature differences between the attic and exterior can trap heat and moisture inside. The moisture vapor condenses on any metal surfaces such as duct work as well as becomes trapped in insulation. When excess moisture builds up, mold damage can begin to take its toll in just a few days. Once it starts to run its course it’s often difficult and costly to get rid of.

Ice dams and the subsequent moisture penetration can lead to mold and mildew in colder climates as well. Without proper ventilation and high insulation R-values, the roof surface temperature can fluctuate and go through several freeze-thaw cycles resulting in ice forming at the eaves. Water continues to back up and freeze behind the ice dams pushing apart shingles or standing seam metal roofs and allowing moisture to penetrate the building envelope. With moisture behind the weatherproofing layers of the roof, mold and mildew is not far behind.

Engineered Ventilation System

One of the best ways to prevent mold from setting in is to maintain proper airflow within the roof system; especially in a steep slope roof.

Atlas Roofing® Corporation now offers the most complete roof ventilation system specifically designed to achieve balanced ventilation and eliminate problems caused by lack of airflow beneath the roof deck. Techni-Flo™ is an engineered ventilation system manufactured for use in steep-slope roof applications. It can be used with shingle or standing seam roofs.

Techni-Flo combines a nailable polyiso insulation product with eave and ridge vents engineered to spec for each individual roof; so each provides a prescribed ventilation capacity.

Polyiso insulation provides the most R-value per square inch available in the building industry. When used in the Techni-Flo system as sheet insulation and vent spacer strips polyiso controls temperature and facilitates cross-ventilation.

The Techni-Flo system creates intake airflow using eave vents specifically engineered for prescribed roofing requirements. The exhaust air flows out of the system through a ridge vent also manufactured to spec, so the air volume moving through the polyiso insulation panels remains consistent and even. When airflow in commercial roofing systems is balanced, temperatures remain constant, potential mold and mildew grow is kept in check and life of the structure is prolonged.