• Extends the life of shingled roofs by minimizing the temperature differential between the attic air and the outside air. It keeps the roof system cool during the hot summer months, preventing premature deterioration and less shingle replacement.
• Extends the life of metal roofs systems by preventing moisture from condensation that develops on the underside of the roof, ultimately causing rust & other structural problems.
• Prevents ice damming caused when the heat from inside the building and the sun melts the snow at the ridge. This causes water to run to the eaves and refreeze and the repetition of this process causes ice dams.
• Provides energy savings in the summertime by cooling the roof sheathing, preventing premature roof deterioration, premature roof replacement and increased servicing of cooling units due to their excessive use. It prevents heat build-up in unvented systems which radiates downward and increases the demand on cooling systems.
• Provides energy savings in the wintertime by preventing hot and cold air to interact and cause moisture from condensation that causes soaked insulation, corrosion and water infiltration.

Ice damming can cause damage to roof coverings, fascia and gutters. Structural damage can occur as a result of the weight from the ice and water pooling inside the dam infiltrates under the shingles, damaging or destroying the shingles. The insulation can absorb water that has pooled from openings caused by ice dams, which causes the R-value to drop and creates an environment for mold, mildew, spores and fungi which can cause health problems.

• ▪ Proper insulation
• ▪ Underlayments
  • Use a waterproofing shingle underlayment 
  • Provides a waterproof barrier under the shingles
  • Prevents water infiltration from pooled water from the ice dams
• ▪ Proper Ventilation
  • Creates a cold roof system so the temperature of the roof sheathing is close to the outside temperature
  • Large amounts of outside air need to be taken into the roof system at the eave and exhausted at the ridge
  • Use our Above Sheathing Ventilation Calculator to help determine the amount of airflow required in your ventilation nailbase system or use our NFA Calculator to determine the proper NFA for attic ventilation.

Warm air rises and cool air descends, therefore, cool air will naturally enter the system through lower eave vents and warm air will naturally exhaust through high ridge vents. A well circulated and balanced system takes advantage of this natural thermal effect.

Wind speed as it moves against and over a building is key rather than the wind’s velocity. This creates high and low pressure zones (Bernoulli’s Principle). High pressures force air into the attic at the eave, while ridge vents create a baffle, causing low pressure to draw air from the ridge and prevent rain and snow from entering the attic.

Net free area (NFA) is the portion of the opening in the vent that actually ventilates; the total unobstructed area through which air can enter or exhaust a non-powered vent. To calculate the needed NFA for your attic system, use our NFA Calculator.

1. Larger structures
2. Longer runs (eave & ridge)
3. Larger surface area of the roof
4. Lower pitches
5. Larger heating and cooling systems, often placed in the attic

Install vents with a balance system of net free vent area. Take into consideration the stack effect, air movement caused by wind and by temperature differences. As a rule of thumb, for every 1” of exhaust air have greater than or equal intake and ensure that you have a balanced system.

Ventilation is only as good as the amount of airflow that is allowed in and out of the system. Most products on the market are designed for residential homes which require lower NFA ratings, which are inadequate for large, commercial roof systems. Most of these products provide inadequate ventilation after a 30’ run and most products provide inadequate ventilation after 75’ widths. Make sure that the products you select will provide proper ventilation for longer runs and widths. To help determine the amount of airflow required in your ventilation system, use our Above Sheathing Ventilation Calculator for ventilated nailbase systems or our NFA Calculator for attic ventilated systems.