Ever since the 1960’s and 70’s, as we built homes more airtight and energy efficient, attic ventilation has become more and more of a critical issue in building science. The chief reason is because of the phenomenon of stack effect, which is discussed in more detail in this video:
From the Air Vent website:
“The constant, year-round movement of air across the attic is a process that can improve home comfort, reduce damage to the roof structure and help keep a roofing warranty valid. Every time stale, overheated air is vented out of the home, and fresh air is pulled in to replace it, you have an “air exchange.”
The process of air exchange is more than a breeze moving through the home. It’s a process that provides a steady, high volume of air movement. It’s a system of components, all sized and positioned to create a balanced flow of intake and exhaust air moving though the attic.”
Before the 1950’s, roof decks were primarily plankboard instead of plywood. In the Norfolk and Newport News area, the use of Cedar Shake Roofs, Slate Roofs, and Nofolk Tile Roofs, and even Asbestos Tile Roofs were common and can still can be found in the areas of Larchmont and Ghent in Norfolk, Hilton Village and Huntington Heights in Newport News and parts of Williamsburg, Virginia. These materials were not as airtight as the current construction methods. Ventilation problems were rarely encountered due to these systems “naturally venting”. With the more modern plywood and asphalt roof shingles, attic ventilation has become a forefront issue in the roofing and building science industries.
In our area of Hampton Roads Virginia, also known as Tidewater, which includes Yorktown, Virginia Beach, Newport News, Williamsburg, Chesapeake, Norfolk, Hampton, Suffolk, Portsmouth, the chief reason for attic ventilation is to prevent condensation and mold growth in the attic space. Other reasons include the prevention of superheating of the attic space which can result in decreased shingle life – most asphalt shingle manufacturers, to include GAF Shingles, Certainteed Shingles, Owens Corning Shingles, Tamko Shingles and IKO Shingles – require proper attic ventilation to validate their shingle warranties.
Here is a great video from Air Vent to explain the issues:
The proper solution for attic ventilation is well established today; put simply, an attic needs intake and exhaust. There are proven ratios for how much ventilation is needed per square foot of attic space. If anyone other than me is interested in actually crunching those numbers, here is how:
The challenge that the industry has run into is what to do about intake ventilation when a home has been built with little to no soffit overhang to allow for vents to be cut into. Many of the homes constructed prior to the 1950’s have this issue.
Some awkward attempts have been seen, probably made by well-meaning roofers, such as installing exhaust vents low on the roof to allow intake air to enter the attic. Uber Home Inspector, Brad Brinke of ProCraft Home Inspections recently shared a picture of this very phenomenon (you might recall Brad previously sending us another debacle picture http://www.jimhicks.com/dont-mix-the-vents-in-virginia-beach/)
Several years ago, I got a call from Bill Taylor at AirVent for some help with their efforts to develop a roof installed vent system to compete with the system by SmartVent that we had been installing. Bill and an engineer flew out from Dallas to meet with us in Yorktown Virginia. We liked the design, made some installation suggestions and took them out to several homes in Newport News, Hampton and Yorktown Virginia. It wasn’t long afterwards that Air Vent brought The Edge to market!
The Edge is a roof installed intake ventilation system that is virtually invisible from the ground. It installs cleanly and is designed to work with AirVent’s Shinglevent Ridge Vent system. It’s well thought out and we have been using it for several years now with fantastic results. It also solves the other, not often admitted challenge, that roofers hate getting off the roof to install intake ventilation!
Learn more about The Edge here:
Mixing exhaust vents on roofs: http://www.jimhicks.com/dont-mix-the-vents-in-virginia-beach/
Tips for a Balanced Ventilation System: http://www.jimhicks.com/technical-corner-tips-for-the-balance-system-for-attic-ventilation-by-air-vent-inc/
Should you add a ridgevent? http://www.jimhicks.com/should-you-add-a-ridgevent-when-you-have-a-new-roof-installed/
While you’re contemplating your ventilation needs this election season, make sure your home votes for Jim Hicks: Pro-Improvement & Anti-Bad Things!
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