Air Vent University
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. Welcome.
Use the Tabs below to switch between lesson plans and quizzes:
Lesson Plans
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. Read why these roofing contractors work hard to avoid it. 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. 
Read the article: What good are Attic Exhaust Vents? They're Not Without Proper Intake Vents
Take the 5-Question Quiz
(Shortened version of the “Ask the Expert” Seminar)
Quizzes
View our July 2020 Lesson Plan: What Size Power Fan Does the Attic Need? To test your knowledge about what you learned in the July 2020 Lesson Plan featuring the calculations used for “What Size Power Fan does the Attic Need?” please take our short 5-question Pop Quiz. Your answers will be “graded” as you go, so you’ll know immediately if you were right or wrong.To add some fun, we’ll send an Air Vent golf shirt to 10 random participants just for taking the quiz, regardless of your quiz answers. We'll select 10 winners at the end of the month. Don't forget to include your shirt size. Good luck!
View our June 2020 Lesson Plan: “What Good are Attic Exhaust Vents? They’re not without Proper Intake Vents,” To test your knowledge about what you learned in the June 2020 Lesson Plan featuring the industry article “What Good are Attic Exhaust Vents? They’re not without Proper Intake Vents,” please take our short 5-question Pop Quiz. Your answers will be “graded” as you go, so you’ll know immediately if you were right or wrong.To add some fun, we’ll send an Air Vent golf shirt to 10 random participants just for taking the quiz, regardless of your quiz answers. We'll select 10 winners at the end of the month. Don't forget to include your shirt size:
To test your knowledge about what you learned in the May 2020 Lesson Plan featuring our ShingleVent II Installation Animation, please take our short 5-question Pop Quiz. Your answers will be “graded” as you go, so you’ll know immediately if you were right or wrong.To add some fun, we’ll send an Air Vent golf shirt to 10 random participants just for taking the quiz, regardless of your quiz answers.
To test your knowledge about what you learned in the April 2020 Lesson Plan featuring our Attic Ventilation Educational video, please take our short 5-question Pop Quiz. Your answers will be “graded” as you go, so you’ll know immediately if you were right or wrong.
Podcast
Airing it Out with Air Vent is a podcast focusing on residential attic ventilation best practices, tips, and solutions. It is an extension of our popular Attic Ventilation: Ask the Expert in-person seminars held for residential roofing professionals across North America every winter. Listen to episodes below, or find us on your favorite Podcast Network.
Episode 3: No amount of attic exhaust ventilation can overcome the lack of intake ventilation at the eave/soffit or roof’s lowest edge. In this episode of Airing it Out with Air Vent, residential roofing pros explain why they ensure attic ventilation includes exhaust and intake. A special thank you to all who contributed to this podcast episode!
Sue McCollum May
Chris Arrington
Jeff Barnett
Clayton Putman
Greg Pike
Sandra Daffer
Sean Jegen
Sean Toms Episode 2: The most qualified people to offer tips and guidance for avoiding mistakes and callbacks are the very people who have first-hand experience with the issue. In this episode of Airing it Out with Air Vent, we asked residential roofing pros to give us their top attic ventilation tips based on what they have seen in the field. A special thank you to all who contributed to this podcast episode!
Scott Dennison
Tom Picha
Sabrina Johnson
Shawn Bellis
Sean Toms
Corey Ballweg
Jeff Heitzenrater
Richard Turner
Jake Jacobson
Trevor Atwell
Tim Chapin
Ron Bastian
Jerry Becker
Sue May
Paul Vosen
Steve DuCharme
A Better Way Construction and Roofing - Lincoln, Nebraska
Arrington Roofing - Dallas, Texas
Barnett Roofing & Siding - Canton, Michigan
Elite Roofing - Denver, Colorado
Campo Roofing - Twinsburg, Ohio
Hawaiian Built Roofing - Boise, Idaho
Gorilla Exteriors Contracting - Shawnee, Kansas
S & K Roofing - Eldersburg, Maryland
Dennison Exterior Solutions - St. Joseph, Michigan
Affordable Roofing - Aurora, Illinois
KDCO Home Improvements - Akron, Ohio
EPIC Exteriors - Overland Park, Kansas
S & K Roofing - Eldersburg, Maryland
Mid Towne Construction - Cross Plains, Wisconsin
Triple Peaks Roofing & Construction - Olmstead Falls, Ohio
RJ Turner Remodeling - High Point, North Carolina
SF5 Construction - Little Elm, Texas
Atwell Exterior Services - Greenville, North Carolina
Your Safe and Healthy Home - Akron, Ohio
Bastian Roofing - Richfield, Wisconsin
Roof Life of Oregon - Tigard, Oregon
A Better Way Construction & Roofing - Lincoln, Nebraska
Degenhardt Home Improvement - Madison, Wisconsin
Innovative Builders Roofing & Construction - Edmond, Oklahoma
Episode 1: Most attics have incorrect or insufficient ventilation. Our survey shows it’s 77% of today’s homes. So What? In this episode of Airing it Out with Air Vent, we dive deep into the potential consequences of improperly ventilated attics and explain why it matters.
