Your Home Attic... To Vent or Not to Vent?

A vented attic without a doubt is the most hostile environment in any home or building. It can reach temperatures of over 150 degrees in the summer below freezing in the winter. Any system operating in such an environment must work harder just to overcome the extreme temperatures. A vented attic will also allow hot moisture laden air to accumulate in the attic and create a condition where the vapor condenses inside the attic. This moisture along with air and cellulose materials are the three basic items needed for the growth of mold and mildew. Venting your home's attic can also allow blowing rain and snow to enter and accumulate on the attic floor or ceiling and very likely cause damage to the sheet rock. Another danger of a vented attic is burning embers entering and causing major structural damage. Burning embers entering attics were blamed for several houses being destroyed recently in Northern California.

Converting your attic into a semi conditioned space in hot climates by closing the soffit, gable, and ridge vents is a positive design approach in reducing moisture loads in houses and buildings. Applying Sealection 500 spray foam to the roof line and making the attic area a conditioned space, you can overcome these problems and will enhance the operation of various systems located in the attic. Moving the duct system from an un-conditioned area into a conditioned space has a major effect on its performance since its insulation is typically R-4 to R-6. Any leakage on the supply side of the system is kept inside the conditioned space and isn't lost to the exterior world. In a vented attic, any air leakage will allow hot humid air, along with dust and allergens to be sucked into the ducts and circulated throughout the house.

New construction homes and buildings achieve on average a 7 to 10 degree difference in temperature from the conditioned living space to the attic by means of Sealection 500's complete thermal package insulating all exterior walls and roof line of the conditioned space. For example, a living area of 75 degrees with a complete thermal package would have an average attic temperature of 82 to 85 degrees. New and existing homes or buildings that only insulate the attic with Sealection 500 foam can reduce the attic temperature by an average of 30 to 45 degrees.

Benefits of Un vented Attics:

• Reduces sensible and latent heat loads.
• Eliminates air infiltration preventing 90 percent of moisture intrusion, 40 percent of energy loss and mold growth.
• Reduces damage from wind driven rain.
• Eliminates condensation on ducts.
• Cuts utility bills substantially.

Building Codes:

To help improve building performance during hurricanes, the Florida Hurricane Advisory Committee changed building codes to support the use of un vented attics. Why? Because during Hurricane Charlie, wind-driven rain through soffits and gable vents was the second highest cause of property damage in the area according to FEMA Research Study 490.
In October 2005, the ICC adopted un vented attic assembly for the 2006 IRC building code based on the conclusion that using low air permeable insulation on the underside of a roof deck is a positive way to improve building performance.