RoofViews

Residential Roofing

How to Plan a Balanced Attic Ventilation System

By Dawn Killough

January 10, 2020

Attic ventilation

When considering replacing your roof, you'll need to calculate the amount of attic ventilation needed to help reduce excess heat and moisture in your attic. Excess heat and moisture can lead to premature roof system degradation and damaging ice dams in the winter.

Let's take a closer look at the process of calculating how much attic ventilation you'll need to to properly ventilate the attic space.

What Is the Balanced Ventilation Rule?

The balanced ventilation rule states that the amount of air coming in from the intake vents at or near the soffit area of the roof should always match that of the exhaust vents at or near the ridge of the roof. This ensures that a balanced amount of air enters and exits the attic space.

Any imbalance of intake and exhaust—such as having more exhaust than intake—can make the system less effective by reducing the amount of warm, moist air that escapes the exhaust vents. A proper amount of intake ventilation will help the exhaust ventilation function more efficiently.

Care must always be taken to avoid mixing different types of exhaust vent products. Using different types on the same attic space can also cause an imbalanced system.

How to Calculate a Balanced Attic Ventilation System

The most effective attic ventilation system is a balanced one, with equal amounts of air coming in and going out. This continuous, balanced flow of air helps to reduce overheating and moisture build-up, which can result in ice damming and damage to your roofing system.

1. Measure Attic Floor Space

Calculate Attic Roof

Start by measuring the square footage of attic floor space. For example, if the attic is 30 ft. wide and 40 ft. long, multiplying those numbers together would reveal a total square footage of 1,200 sq. ft.

2. Calculate the Net Free Ventilation Area

Calculating the Net Free Ventilation Area (NFVA) uses the 1:300 rule. Let's dig a bit deeper:

What Are NFVA Ratings?

NFVA is a measure of open area in a roof vent that allows for air to move through it. Also called Net Free Ventilation (NFV) or Net Free Area (NFA), this rating is used to determine how much airflow is needed for the total attic space, as well as how much is needed for intake and exhaust. The types and quantity of roof vents are calculated based on this measurement.

What Is the 1:300 Rule?

The US Federal Housing Authority recommends a minimum of 1 square foot of attic ventilation for every 300 square feet of attic floor space, evenly split between intake and exhaust.

The NFVA is calculated by dividing the total attic square footage by 300, the minimum recommendation for a balanced ventilation system, or the number stipulated by local codes. In our example, we divide 1,200 by 300 to get 4 sq. ft. NFVA needed for attic space.

Most roof ventilation products come with a NFVA rating in square inches, not square feet. To convert the NFVA for the attic space into square inches, multiply it by 144, the number of inches in a square foot. In our example, 4 times 144 equals 576 sq. in. NFVA.

A balanced ventilation system requires equal intake and exhaust. To find out how much ventilation is needed for each side of the system, simply divide the NFVA in square inches in half. In our example, we divide 576 in half and get 288 sq. in. NFVA needed at both the intake (at the soffits) and exhaust (at the ridge).

Intake and Exhaust

3. Select the Right Intake and Exhaust Ventilation Products

The next step is to select the correct ventilation products for your attic. The GAF attic ventilation calculator can tell you the types and quantities of vents that you'll need for your roof based on your attic dimensions.

You can also visit the GAF ventilation and attic vents product page to help you select the intake and exhaust vents for your roof. It's important to consult with a local roofing contractor for advice on the best products for your specific property and house.

4. How to Place Intake and Exhaust Ventilation

Intake ventilation is installed at the lowest part of the attic space, generally at the soffit or base of the roof. Exhaust ventilation is installed at the highest part of the attic space, which is typically at the ridge or apex of the roof.

Homeowners should always discuss the placement of their intake and exhaust vents with a professional.

How Do You Size a Power Attic Vent?

If you're looking to utilize a powered attic vent to help reduce heat and moisture from your attic space, it's important to remember that it should never be mixed with ridge vents or other types of non-powered exhaust vents. Typically, powered attic vents are rated by the amount of square footage they can ventilate. By calculating your total attic floor square footage, you can then figure out the number powered attic vents needed to properly ventilate your attic space.

For more information about calculating and planning a balanced ventilation system for your attic, consult with a contractor certified by GAF*.



*Contractors enrolled in GAF certification programs are not employees or agents of GAF, and GAF does not control or otherwise supervise these independent businesses. Contractors may have agreed that they will use GAF roofing products, and may receive benefits, such as loyalty rewards points and discounts on marketing tools from GAF for participating in the program.


About the Author

Dawn Killough is a freelance writer in the construction, finance, and accounting fields. She is the author of an ebook about green building and writes for construction tech and green building websites. She lives in Salem, Oregon with her husband and four cats.

Related Articles

GAF Roofing Academy Graduate holds up his certificate of achievement.
In Your Community

How Attending the GAF Roofing Academy Changed One Graduate's Life

Meet Austin Teague, recent GAF Roofing Academy graduate who shares his transformational journey from ball field to the roof. Prior to the GAF Roofing Academy, he was involved in sports, worked in customer service, but lacked the experience needed to break into the roofing industry. Once he graduated from the GAF Roofing Academy, doors were then opened for him, leading to well-paying jobs as an installer and later as a salesperson, where he is currently on track to meet his financial goals.Attending the two-week program proved to be a life-changing decision for Austin, providing him with the tools and confidence needed to succeed. The course not only equipped him with technical expertise, but also instilled in him the ability to educate customers effectively. Take a listen as Austin shares his story of how he found clarity and direction in his professional life, enabling him to thrive in the industry and build a successful future for himself and his family.Are you interested in a career in the roofing industry? Look for a Roofing Academy course in your area. Video TranscriptMy name is Austin Teague. I'm originally born in Tyler, Texas. Moved to Washington when I was a kid at ten. Well, prior to joining the Roofing Academy and, you know, taking my skills to that test, I was sports, strictly sports. Everything in my life I would, you know, I'd work a customer service job. I was in the, you know, the retail industry. I worked at Walgreens, but my personal life was hectic. It was football practice, baseball practice. It was always something going on.There was always something to do. Everything when it comes to roofing, for me, started after the Roofing Academy. When I tried to get into the roofing industry before going to the Academy, nobody wanted me because I had no experience. They're going to have to train everybody on the job. But because of the roofing academy, because I knew what I was going to do day one, I knew what my job was. I couldn't run into any hiccups because I knew what showing up day one was going to look like.[00:00:56.770]So they gave me a GAF certificate with my name, the location I trained out of, and then when I graduated. And what I did with that is I took it to every single applicant or job interview I had because I wanted them to know that I have this certificate. Not saying I have it, but also bring it, so they can see it.After the academy, I landed a job at 28 an hour as an installer, which is substantial in this living, making life, making payments. And then after that, I got bumped up to 32 an hour when I was working in New Mexico. And now that I'm sales, I'm straight commission. But in this month, I'm on pace to hit 20,000. Our goal at Tristate is to educate the customers firsthand. So being at the Roofing Academy allowed me to know roofing like the back of my hand. As an installer, as a sales, as an owner, you got to see the value in the systems. And it allowed me in my head to build those value, actually explain it to the customers. Where is this number coming from? Well, it's coming from this material because this material is going to cost more, of course, but it's obviously better.[00:01:58.920]I think someone coming to the Roofing Academy right away, no experience, is going to set you up for success. That's what you want. You want to be set up for success. You want to be as many tools as you can in your tool belt to get you to that point you want to be in life. And showing up to the Roofing Academy, it changed my life drastically. I didn't know what I was going to do. I literally didn't know, if roofing wasn't the pathway for me- what was the next plan?I was just grateful. I mean, I was one day on indeed looking for jobs and I saw the Roofing Academy post on indeed looking for academy students, and I thought, why not? What's two weeks out of my life that I get to change it? If I get an opportunity to change it and that two weeks changed my life. There's no time wasted. You're here from nine to three or nine to four at the latest for your classes.You're with guys that you actually enjoy being around. The guys in my class or in the class today, they're fun guys. They all get to make mistakes and learn from each other. And it just makes me grateful that I got that opportunity to make something of myself. I'm not just another guy on the street.[00:03:00.340]I don't know what my life's going to look like in the next six months, but I guarantee it's not going to slow down. I'm going to work harder than ever. I know I got two kids at home. I have something to push me. I would say that all the success started with the Roofing Academy because my life before the Roofing Academy was kind of on a snowball effect. It had started from when I left college and then came home and it kind of just started snowballing. One thing after another was another problem, another problem. Bills at 18, going into debt. You're 18, your life isn't, you're going to ruin your life already. So you got to figure some out. And I figured it out. I got lucky enough that I found GAF and you know they still treat me well to this day. I have my Academy teacher's phone number and I call them up and help him out from time to time, and he helps me out from time to time.We still get along. And it was two weeks of my life that I knew the guy, and he still gives me a call and checks up on me and tries to: How are you doing in roofing? You still in roofing? You still making a name for yourself? You still doing what you said you were going to do? And I am. It's just good to have someone to talk to. Even if you're in this industry for ten years, I guarantee you GAF CARE will probably still give you a call and check on you. That's just what they do.

By Authors GAF Roof Views

April 12, 2024

Roofer climbing a ladder leaning against the roof of a house.
Residential Roofing

What Are Ladder Hooks?

As a roofing contractor, keeping yourself and your employees safe is crucial, which involves using the right equipment. Ladder hooks, sometimes referred to as roof hooks, are used to secure a ladder over the top of a roof's ridgeline. They're an essential piece of safety equipment for steep-slope roofing work.How Do Ladder Hooks Work?These hooks resemble a shepherd's crook that hooks over the roof's ridgeline and stays put with an attached T-bar to secure it to the other side of the ridge. The bottom of the crook has a smaller hook that holds the ladder and prevents it from slipping or sliding down the roof. Ladder hooks are typically made from heavy-duty steel and can support several hundred pounds. They essentially turn the ladder into a more stable set of stairs, creating a safer and more efficient work environment for roofing professionals, especially during steep-slope work.Most hooks also feature a rubber wheel that can help you get the ladder safely up onto the roof. Once you secure the hook on the rungs of the ladder, roll the ladder up the slope (on its back). When it passes the roof ridgeline, flip the ladder over to secure the hooks over the top of the ridgeline.Why Should You Use a Ladder Hook?According to the American Ladder Institute, 500,000 people are treated for injuries from using ladders every year, with 300 of those injuries leading to fatalities. With newer home styles featuring more dramatic rooflines with steep pitches, you may find yourself facing 10:12, 12:12, and higher pitches more regularly. Ladder hooks can help make working on these roofs safer.They can provide stability and security on lower-pitched roofs, too. You may also want to use them for performing repairs around skylights or chimneys, especially if the roof surface is icy or slippery. And they can provide secure footing in cases of suspected damage, such as a weak or rotting deck.These safety devices are designed to prevent the ladder from damaging shingles, so there's no downside to using them.Can a Ladder Hook Replace Other Safety Measures?Using a ladder hook can make you feel more secure and stable on a steep pitch. But you shouldn't forego other safety measures, such as using a personal fall arrest system consisting of lifelines, lanyards, and deceleration devices attached to an anchor point and connected to the body harness. Remember, the anchorage should be able to support 5,000 pounds per employee. Ladder hooks are designed to secure the ladder to the rooftop—not to secure a person or prevent them from falling.How Do You Choose the Right Ladder Hook?To find the right ladder hook, contact your ladder's manufacturer to see if it has a hook designed to work with its ladders. If it doesn't offer any, review the ladder hook manufacturer's guidelines to see what types of ladders are best suited for its hook. If your ladders are due for replacement, you can also look for manufacturers that offer kits with both the ladder and the hook.For more learning opportunities and resources to help you succeed in your roofing business, visit the GAF Center for the Advancement of Roofing Excellence (CARE).

By Authors Karen L Edwards

March 18, 2024

Aerial view of asphalt shingles for a roofing project
Your Home

5 Types of Roofing Technology That Make Buying a Roof Easier

For years, replacing your roof meant scheduling an in-home visit with a salesperson, looking at shingle colors on sample boards, and then waiting days or weeks to receive a written quote. But recent advancements in roofing technology have simplified the process for both contractors and homeowners. You can now quickly and easily visualize the design, estimate material costs, and establish a project plan before work begins.Whether you're buying a new roof or simply having it repaired, here are five of the latest advancements in roofing technology that could help your planning process.1. Design ProgramsWhen purchasing a new roof, choosing the color can be one of the hardest parts. The shingles you choose will protect your home for years to come, so you want to ensure the color complements your home and neighborhood. But it can be challenging to imagine what the finished roof will look like.Fortunately, technology has simplified this part of the process. Programs such as GAF Virtual Remodeler allow you to upload a photo of your home (or choose a model home) and virtually try on different colors and styles. You can feel confident about your design decisions before you purchase materials.2. Aerial ImageryContractors can use high-resolution aerial imagery to see a bird's-eye view of your home and assess your roof's current condition, depending on how recent the satellite image is. They can evaluate the roof's health, deem whether certain areas of your surrounding property need to be protected, and note any extra safety precautions that might be necessary for the work.The imagery tool helps speed up the overall process. Contractors don't need to come out to your home to understand the complexity of your roof, and you don't need to make time in your schedule for a site visit.3. Aerial Measurements and Estimating SoftwareGoing a step further, technology companies have combined aerial imagery with other software programs to calculate the measurements of a home's roof. These measurements are then input into estimation programs and used to quickly generate a material estimate for your new roof's installation.This means you can receive your project estimate within hours—not days—and you can be confident in the estimate's accuracy. Once you know the total cost of the materials, you can better plan your budget.4. All-in-One Project PlatformsIn an attempt to provide a high level of customer service and satisfaction, many roofing professionals have been tapping technologies provided by the manufacturers themselves. These all-in-one platforms streamline the roofing sales process, allowing contractors to remotely perform a number of tasks and virtually collaborate with homeowners, while ensuring they are using the most accurate and up-to-date information from the manufacturer.Using these kinds of digital tools, roofing professionals can inspect your home to create estimates. They can then meet with you virtually (or schedule an in-person consultation, if you prefer) to review your project and the related options for your home. You can also sign your contract and easily make your payment electronically.5. Online Shopping ToolsEvery day, millions of homeowners shop online for essential items that get delivered to their doors. Since there's nothing more essential to your home than its roof, why not research and buy yours online?That's exactly what GAF Master Elite Contractor Gunner Roofing owners Andrew and Eddie Prchal had in mind when they developed the Gunner Estimator. The brothers designed the program to enable homeowners to shop online for a roof. With a focus on improving the overall customer experience, the Prchals wanted to take the hassle out of purchasing a roof. The result is a roofing technology that provides a seamless process for homeowners.Creating an Intuitive ExperienceAll of these technological advancements help to streamline the process of getting work done on your roof, saving you time and potentially money. Whether you're getting your roof repaired or completely replaced, roofing technology can assist. Ready to get started on your new roof? Look for a certified contractor,* with access to roofing technology programs provided by GAF.*Contractors enrolled in GAF certification programs are not employees or agents of GAF, and GAF does not control or otherwise supervise these independent businesses. Contractors may receive benefits, such as loyalty rewards points and discounts on marketing tools from GAF for participating in the program and offering GAF enhanced warranties, which require the use of a minimum amount of GAF products. Your dealings with a Contractor, and any services they provide to you, are subject to the GAF Contractor Terms of Use.

By Authors Karen L Edwards

March 18, 2024

Don't miss another GAF RoofViews post!

Subscribe now