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Posts Tagged ‘NFVA’

Are Your Shingles Warranted?

Wednesday, October 14th, 2009

Shingle manufacturers require that roof systems in which it roof shingles are installed meet HUD or local building code standards for ventilation. If your home does not meet the minimal requirements, your warranty may be void in whole or part.

How do you know if your home has a properly vented attic?

You must understand what Net Free Ventilation Area (NFVA) is and how to calculate yours. NFVA is a ratio based on the total amount of square footage in your attic and the amount of square footage used to vent, through intake vents, (i..e. continuous soffit vents, under eave vents, drip edge vent, etc) exhaust vents (i.e. roof louvers, gable louvers, ridge vents, etc.) power attic fans, etc.

Working in the rafters.

The HUD standard for a balanced home using 50% intake and 50% exhaust is 1 square foot of venting for every 300 square feet of attic space, noted as 1/300. If your home only uses intake vents that ratio reduces to 1/150. For example: if you have an older home which only uses soffit venting and the attic square footage equals 2,000 – then you must have a minimum of 13.33 square feet of soffit vents to comply with most roofing material warranties.

Before you purchase new roofing material, make sure you know what they require for NFVA and confirm your home meets those requirements. Also, if you are building a new home take some time to look at attic venting options. This can save you in energy costs, air quality, and moisture control which are as important as roofing warranties.