Air Vent is committed to helping roofing professionals everywhere by collecting and sharing best practices and solutions in residential attic ventilation. Air Vent University is an extension of this commitment. Here you’ll find useful information to help you in the field now and as a reference for the future. We’ll add new “lesson plans” regularly. We’ll also mix in some fun with pop quizzes and occasional prizes. And check out our podcast, too. Welcom. For additional learning opportunities, see our Education page.
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Tips for Venting Hot Attics That statement is extracted from a recent article by Air Vent published by Western States Roofing Contractors Association. Read the full story here: Vent Those Hot Attics Carefully Homeowner’s Energy Bill Cut 25% Thanks to Attic Ventilation The statement above is from our one-on-one podcast interview with Khaled Kazmi, roof specialist, Precision Roof Crafters, Houston, TX. Listen to the entire episode in which Kazmi details the red flags he found inside the attic, how his team fixed the problems, and the reaction from the very pleased homeowner. Improper Attic Ventilation Can Reduce Shingle Life 24% The statement above is from one of the 15 roofing professionals who shared their first-hand experience with premature shingle deterioration due to incorrect or zero attic ventilation. Read the full story here: The Impact of Attic Ventilation on Shingle Life. Getting Insurance to Pay to Bring Attic Ventilation Up to Code This statement from an episode of our podcast Airing it Out with Air Vent was said by Kyle Pyatt, Gen 3 Roofing Corporation, Centennial, CO. The episode focuses on the various ways to get homeowner’s insurance to pay for proper attic ventilation during a storm-damaged roof replacement claim. One of the clearest paths to the insurance company agreeing to pay is the insurance policy itself. But there are other ways, too. Attic Ventilation Per Building Code: IRC 2021 Every three years the International Residential building Code is reviewed for updates and then released. Residential attic ventilation is Section R806. In the 2021 IRC, the minimum amount of attic ventilation remains 1/150 (1 square foot of Net Free Area for every 150 square feet of attic floor space. Attic floor is defined as length x width FLOOR of the attic). You can read the code here: 2021 International Residential Code for One- and Two-Family Dwellings Invest in Yourself and Your Business with Continuous Education “If you want to be best in this industry, in your business or in your personal life, then continuous education is crucial.” This statement taken from an episode of our podcast Airing it Out with Air Vent was said by Kevin Marcano, Marcano Roofing, Salem, OR. The episode focuses on the benefits everyone in your business can receive through ongoing learning – including the person who answers the phone. Attic Ventilation is NOT Just a Summertime Concern Balanced attic ventilation is important and provides benefits year-round. Battling heat in the summer is commonly known. But equally important is the fight against wintertime moisture. Edge Vent Passes 30-Day Ice Dam Test Installing a roof-top intake vent at the edge of the roof for houses in climates battered with snow and ice may cause you to wonder: What happens if an ice dam occurs? This test answers the question. Fact or Fiction? Mixing Exhaust Vent Types is Problematic Never mind what the Installation Instructions, what the shingle manufacturers, and what building code say. Forget all of that. What do roofing professionals across North America say they have witnessed when the project they are working on has pre-existing mixed types of attic exhaust vents on the roof? How Does Proper Attic Ventilation Protect My Roof? (ARMA Video) Every home has a roof, but is every roof properly ventilated to help prevent roof deterioration or roofing system failure? In this short video the year-round benefits of attic ventilation are highlighted so roofing professionals can better understand them and easily share them with homeowners. Video courtesy of Asphalt Roofing Manufacturers Association (ARMA) Lean on Air Vent to Help Educate the Homeowner A roofing contractor interviews Air Vent “Ask the Expert” seminar host Paul Scelsi in two quick minutes to boil down the “How’s and Why’s” every homeowner should factor in when it’s time for a new roof. NOTE: If you’d like your own customized short video with Paul, send us an email and perhaps we can arrange it via a Microsoft Teams video chat (pscelsi@gibraltar1.com). Video interview courtesy of Drew Cope, Cope Construction & Renovation, Kelton, PA. Sizing NON-MOTORIZED Attic Vents for the Attic To help you determine how many NON-MOTORIZED attic exhaust vents are needed for an attic (as well as the intake vents required for those exhaust vents to perform properly), Air Vent has three different tools you can use.
1. Use the Air Vent App for iOS and Android devices. It’s free, easy to use and has many additional features beyond a built-in calculator.
2. Use the Air Vent Online Calculator in either its web-based version or the jazzed up spreadsheet that is customizable with your company colors and personalized text message to clients. It’s free as well.
3. Calculate it yourself by hand. You never know when a client may ask you, “Can you walk me through the math used to calculate that?”
• Step One: Determine the attic square footage (measured length x width, floor of the attic). If you cannot measure the attic floor, an acceptable Plan B measurement is the footprint of the house aerial view.
• Step Two: Determine the Net Free Area (NFA) needed in total for the entire attic. (Note: Non-motorized vents are specified in terms of Net Free Area – the clear, unobstructed area a vent has through which air can move.) To do that, divide the attic square footage by 150 (This is based on the 1/150 ratio of attic ventilation; which is 1 square foot of NFA for every 150 square feet of attic floor space. If you want to use the 1/300 ratio, divide attic square footage by 300.) The resulting number is the total amount of NFA in square feet needed for the attic.
• Step Three: Balance the attic ventilation by determining the NFA needed for EXHAUST VENTS and for the INTAKE VENTS. Using the results from Step Two, divide by 2 because proper attic ventilation is balanced between EXHAUST VENTS (which will be installed at or near the peak of the roof) and INTAKE VENTS (which will be installed in the soffit/undereave or low on the roof). The resulting number is the total amount of NFA in square feet needed from the EXHAUST VENTS and the total amount of NFA in square feet needed from the INTAKE VENTS. Next, multiply by 144 (the number of square inches per square foot) because non-motorized vents are specified in square inches not square feet. You now know the NFA needed in square inches for EXHAUST as well as for INTAKE.
• Step Four: Select the EXHAUST and INTAKE Vents Desired and Determine the Quantity. It’s time to pick both the EXHAUST VENT and the INTAKE VENT suitable for the size and design of the roof/attic. Once that is done, learn the vents’ NFA as rated by the manufacturer. Use that NFA number to determine the quantity by dividing the “NFA Needed” by the actual “NFA the vent provides.”
Here’s an example of the math start to finish.
Step One: (measure the attic) 40 feet length x 50 feet width = 2,000 square foot attic.
Step Two: (determine the NFA needed for the entire attic) 2,000 ÷ 150 = 13.3 square feet of NFA in total needed for the entire attic.
Step Three: (balance the system with EXHAUST and INTAKE vents).
‣ 13.3 square feet of NFA ÷ 2 = 6.7 square feet of EXHAUST ventilation needed as well as 6.7 square feet of INTAKE ventilation needed.
‣ (convert to square inches by multiplying by 144) 6.7 x 144 = 965 square inches of EXHAUST net free area needed, and 965 square inches of INTAKE net free area needed.
Step Four: (select the EXHAUST and INTAKE vents desired; determine quantity).
‣ Select an INTAKE vent desirable for the project, determine its net free area rating in square inches per unit/linear foot.
✓ For example, an 8 x 16 rectangular undereave vent allows 56 square inches of net free area per unit. Thus, 965 ÷ 56 = 17 rectangular undereave vents needed.
‣ Select an EXHAUST vent desirable for the project, determine its net free area rating in square inches per unit/linear foot.
✓ For example, ShingleVent II ridge vent is 18 square inches of NFA per linear foot. Thus, 965 ÷ 18 = 54 linear feet of ridge vent needed.
What Size Power Fan Does the Attic Need? To help you size a roof-mount or gable-mount power attic fan (whether traditional electric or solar powered) for an attic, Air Vent has three different tools you can use.
1. Use the Air Vent App for iOS and Android devices. It’s free, easy to use and has many additional features beyond a built-in calculator.
2. Use the Air Vent Online Calculator in either its web-based version or the jazzed up spreadsheet that is customizable with your company colors and personalized text message to clients. It’s free as well.
3. Calculate it yourself by hand. You never know when a client may ask you, “Can you walk me through the math used to calculate that?”
• Step One: Determine the attic square footage (measured length x width, floor of the attic). If you cannot measure the attic floor, an acceptable Plan B measurement is the footprint of the house aerial view.
• Step Two: Determine the CFM needed from the power attic fan to service the attic. Multiply the attic square footage by a factor of 0.7 (this produces 10-12 air exchanges per hour from the power attic fan). The resulting number is the CFM (Cubic Feet of air moved per Minute) needed from the power attic fan to properly exhaust the attic. Find a power attic fan with the required CFM or close to it. NOTE: It’s OK to have more CFM than needed as long as the fan(s) are given the necessary amount of intake ventilation (at the soffit/eave or low on the roof near its edge). That’s the next step.
• Step Three: Give the power attic fan proper intake ventilation. The amount of intake ventilation a power attic fan needs is based on its CFM. If the attic requires more than one power attic fan, this formula applies to each fan used or installed for the project. Here’s the formula:
‣ CFM of the power attic fan ÷ 300 = Square feet of intake net free area needed.
‣ Since intake vents are rated/specified in square inches (not square feet), it’s necessary to convert from square feet to square inches. That is easily accomplished by multiplying by 144 (the number of square inches per square foot).
‣ Once you know the intake ventilation net free area needed in square inches, find an intake vent best suited for the project, identify its net free area in square inches (each manufacturer should publish that number) and determine how many units/feet of intake vent are needed.
Here’s an example of the math start to finish.
Step One: (measure the attic) 40 feet length x 50 feet width = 2,000 square foot attic.
Step Two: (determine CFM of the fan needed) 2,000 x 0.7 = 1,400 CFM power attic fan needed.
Step Three: (give the power attic fan proper intake ventilation).
‣ 1,400 ÷ 300 = 4.7 square feet of intake ventilation net free area needed.
‣ (convert to square inches by multiplying by 144) 4.7 x 144 = 677 square inches of intake ventilation net free area needed.
‣ Select an intake vent desirable for the project, determine its net free area rating in square inches per unit/linear foot.
‣ For example, an 8" x 16" rectangular undereave vent allows 56 square inches of net free area per unit. Thus, 677 ÷ 56 = 12 rectangular undereave vents needed.
What Good Are Attic Exhaust Vents? They’re Not Without Proper Intake Vents Overlooking intake ventilation is the #1 mistake in residential attic ventilation. ShingleVent II Installation Animation In this quick video you’ll see how our four-foot stick ridge vent ShingleVent II installs, including roof pitch requirements, slot cut and the ever important, often overlooked intake ventilation needs. Hope you find it helpful. Attic Ventilation Educational Video This video is extracted from the annual Air Vent Seminar “Attic Ventilation: Ask the Expert™” held in-person for roofing professionals across North America every 1st quarter. The seminar is an overview of residential attic ventilation best practices, solutions, categories of intake & exhaust vents, and much more. Ask the Expert Seminar: Early Notification To be added to the email list to attend a future in-person seminar, please add your email address below, and we'll notify you when our annual Ask the Expert schedule is announced. Click here for additional information about the “Attic Ventilation: Ask the Expert™” seminars. “There’s no doubt proper attic ventilation can impact the effectiveness of the air conditioning system. But here are some common mistakes roofing contractors see in the field as a result of someone trying to help the A/C. In some cases, these mistakes are more problematic than the struggling air conditioning.”
“As I was ready to pull the attic access door open the homeowner warned me, ‘Prepare yourself.’ As soon as I opened the attic door it felt like a sauna…I told the homeowner the attic ventilation correction that I’m proposing is going to be huge based on what I’m seeing.”
“When we arrive at a home and begin to climb the ladder and we are greeted with excessive granules in the gutter, we know we have a premature shingle deterioration situation. The homeowners often report that the roofing system is new and that they were sold a lifetime roofing system. Without even having to look, we know the answer: They were sold a ‘lifetime roofing system,’ but sadly one without ‘lifetime ventilation.’ ”
Read the full article here: The Impact of Attic Ventilation on Shingle Life
Listen to our Podcast episode “Improper Attic Ventilation Reduces Shingle Life 24%”
“If you’re working with a municipality that does not even enforce the building code…send the insurance company specs from the shingle manufacturer as it pertains to attic ventilation.”
Listen to our Podcast episode “Getting Insurance to Pay to Bring the Attic Ventilation Up to Code”
Learn More: Handy Checklist to Get Insurance to Pay for Proper Attic Ventilation
Listen to our Podcast episode “Invest in Yourself and Your Business with Continuous Education”
Read the Test Summary: Edge Vent Passes 30-Day Ice Dam Test Highlights
Read the article: Fact or Fiction? Mixing Exhaust Vent Types is Problematic
Read why these roofing contractors work hard to avoid it.
Read the article: What good are Attic Exhaust Vents? They're Not Without Proper Intake Vents
(Shortened version of the “Ask the Expert” Seminar)
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