Dwight Cline, Florida Sales Manager, O’Hagin LLC
Ventilation codes in roofing are often overlooked, misinterpreted or, in some cases, unenforced. This combination of issues can lead to a shortened roof life, voided warranties and even health complications from mold or viral particle accumulation. Ultimately, all of these concerns fall on the shoulders of our customers, the homeowners. As licensed roofing professionals, we strive to provide the best products at the best price, solving problems and fulfilling the needs of our customers. The purpose of this article is to equip roofing professionals with the information they need to confidently navigate the industry, resulting in better, stronger and longer-lasting roof systems.
In this article, I will cover the importance of ventilation, Florida Building Codes and the science behind why proper ventilation is essential for roof systems.
Ventilation plays a crucial role in protecting three key areas: the homeowner, our investments and our warranties and insurance. A common misconception about ventilation is that its primary purpose is to cool homes and reduce energy bills. While that is true to some extent, it is actually a secondary benefit of ventilation.
The primary purpose is much more critical to the longevity of the roof system and the health of the occupants.
Research has shown that the average person generates approximately three-quarters of a gallon of water vapor each day through activities such as cooking, cleaning and simply perspiring. Without proper ventilation, this moisture accumulates in attic spaces, leading to the growth of mold and mildew. Mold and mildew are notorious for their rapid growth in warm, dark environments like attics. Left unchecked, they can spread quickly, leading to significant health risks for homeowners. Proper ventilation allows the necessary airflow to carry this excess moisture out of attic spaces, preventing the harmful effects of mold and mildew.
Proper attic ventilation also plays a role in preserving the energy efficiency and integrity of a home’s other investments. Homeowners are increasingly focused on energy efficiency and are making significant investments in upgrades like new doors, windows, insulation and solar panel systems. With new windows and doors, homeowners are often unknowingly tightening the building envelope, preventing moisture from escaping as it once did. This trapped moisture accumulates in the attic, where it can condense onto ceiling insulation, diminishing its R-value. Even if the insulation dries out, it does not regain its original insulating properties.
Another critical aspect of proper ventilation is its connection to roof warranties. Many manufacturers require adequate ventilation to validate their warranties. The reasoning behind this is simple: roof materials need to perform at their best to provide long-lasting protection. When a roof is improperly ventilated, heat buildup can cause shingles and underlayment to degrade, leading to issues such as blistering, curling and granule loss. These problems can shorten the life of a roof system, directly affecting homeowners and their wallets.
In addition, insurance companies are increasingly focused on roof integrity. Many are sending out nonrenewal notices or offering higher premiums for homes with older or improperly ventilated roofs. A properly ventilated roof system that is built to code lasts longer, gives insurers more confidence and reduces the likelihood
of nonrenewal.
To fully appreciate why adequate ventilation is necessary, it’s helpful to understand the science behind it. Two key concepts are convection and the Coriolis Effect. Convection is the process by which heat rises through air or water. In this case, heat from the attic floor needs a way to escape and proper ventilation allows this process to occur efficiently. The Coriolis Effect, caused by the rotation of the Earth, influences air movement, which helps heat rise and move out of the attic space.
The Florida Building Code specifies that for every 150 square feet of attic floor space, one square inch of net free ventilation area (NFVA) is required. This requirement includes all enclosed attic areas, such as garages and non-livable spaces. However, there are two exceptions to this code. First, some climate zones allow for a ratio of one square inch of NFVA for every 300 square inches of attic space, though this exception does not apply to Florida. The second exception requires that 40-50 percent of the ventilation be placed in the upper portion of the roof, three feet from the ridge, creating a balanced system. This balance is essential for ventilation to work effectively. A properly balanced system ensures that intake and exhaust vents align, creating a cross-breeze to facilitate airflow.
In Florida, meeting the 1/300 ratio with a balanced system is the most cost-effective and efficient way to comply with building codes while ensuring the longevity
of roofing systems. By doing so, we can validate manufacturer warranties, extend the lifespan of roofs and address the concerns of the insurance industry. The ultimate goal for all of us – builders, contractors, manufacturers and building officials – is to understanding and adhere to the proper ventilation code.
Through better ventilation practices, we can provide safer, longer lasting and more efficient roofs for our customers, all while protecting our own business interests and reputation. By taking these steps, we contribute to a stronger, healthier roofing system for everyone involved.
Dwight Cline is the Florida Sales Manager for O’Hagin LLC, where he specializes in technical and code training. Dwight is a member of FRSA’s Codes and Governmental Affairs Committees and the Young Professionals Council. He can be reached at dcline@ohagin.com.
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