Readers were asked to rank the industry’s foremost material suppliers to determine who is a true “Brand Leader” and GAF ranked No. 1 for ridge vent systems in the categories of:
- Brand Familiarity
- Brand Used in the Past Two Years
- Brand Used the Most
- Highest Quality Brand
“We are thrilled to be recognized as a ‘Brand Leader’ in all categories for our ridge vent systems. We focus on the importance of ventilation and always strive to make high-quality products, so this honor serves as support for our efforts,” states Ted Marcopolus, vice president of marketing services at GAF.
The 2015 Remodeling Brand Use Study was conducted by the Farnsworth Group to profile brands used by remodelers in specific areas. Readers were asked about their familiarity, use and opinions about brands in 58 product categories, as well as the importance of factors influencing brand selection within each product category. Seven hundred and twenty-one surveys were completed online with professionals classified as “Remodelers, General Contractors, or Replacement Contractors” whose work consists of at least 50 percent repair/remodel. Another 274 professionals answered at least some of the questions.
Good news, roofing contractors: You do not have to be good with numbers nor do you have to enjoy math to be able to quickly—and accurately—calculate the amount of attic ventilation needed for residential attics. Here it is, a handy shortcut for quick calculations:Attic square footage ÷ 2 = square inches of EXHAUST and square inches of INTAKE Net Free Area (NFA) needed. (NFA is the unobstructed area through which air can pass through a vent, usually measured in square inches. Ventilation manufacturers assign an NFA value to the non-motorized vents they make.)
This shortcut conveniently calculates the 2015 International Residential Building Code MINIMUM (IRC Section R806 – Roof Ventilation 1, which states, in part, 1 square foot of Net Free Area for every 150 square feet of attic floor space with the attic defined as length x width floor of the attic). The shortcut actually overestimates a bit but that’s OK. It puts the roofing contractor in the ballpark which is useful when estimating.
To calculate the allowable IRC EXCEPTION to the MINIUMUM (that is, 1/300 ratio) here’s the shortcut:
Attic square footage ÷ 4 = square inches of EXHAUST and square inches of INTAKE Net Free Area needed.
Here’s an example using the shortcut for the 1/150 Code Minimum.
Say the contractor is standing in front of a house that has an attic with 2,200 square feet.
2,200 ÷ 2 =
- 1,100 square inches of EXHAUST net free area needed
- 1,100 square inches of INTAKE net free area needed
The next step is to select a suitable exhaust vent and intake vent that fits the roof design for best performance and best aesthetics. After that, find out the vent’s NFA as rated by the manufacturer. Divide the vent’s NFA into 1,100 to yield the number of vents needed (either in linear feet or units/pieces). That’s it. It’s time to install.
There is a longer “official” formula based on building code you can reference or point your clients to for reassurance that you know what you’re talking about. Most attic ventilation manufacturers list the longer formula on their websites and inside key product brochures. But the shortcut is just as good and faster!
Calculation Q & A
Here are the answers to the five most frequent questions pertaining to calculating attic ventilation.
1. “Why is it important that the amount of intake ventilation matches the amount of exhaust?”
The goal of an effective attic ventilation system is to help fight heat buildup inside the attic during the warmer months and moisture buildup in the colder months. Additionally, in climates where snow and ice are common, attic ventilation can help fight the formation of ice dams. To achieve these goals the attic needs cooler, dryer air entering low (near the eave or the roof’s lowest edge) so it can flush out any warm, moist air that may have built up inside, pushing it out through the roof’s exhaust vents positioned as close to the peak as possible. This balanced-airflow approach allows the air to “wash” the entire underside of the roof deck from low to high.
2. “What if it’s not possible to balance the attic ventilation system 50 percent intake/50 percent exhaust?”
If it cannot be balanced it’s better to have more intake than exhaust because it has been our experience most attics lack proper intake ventilation, which is the leading cause of venting callbacks. Additionally, any excess intake will become exhaust on the leeward side of the house because the intake vents on the windward side of the house will have “pressurized” the attic. As a result, the intake vents on the leeward side of the house will work “with” the exhaust vents to release air.
However, if the attic has more exhaust than intake it potentially can cause the extra exhaust to pull its missing intake from itself (if it’s a ridge vent) or from another nearby exhaust vent (from one wind turbine to another or one roof louver to another), which means possible weather ingestion.
3. “What if the roof has 40 feet of available ridge length but the math calls for only 30 feet of ridge vent needed?”
It is OK to install all 40 feet of ridge vent as long as it can be balanced with intake ventilation. If the amount of intake ventilation cannot match the entire 40 feet of ridge vent, consider reducing the width of the ridge vent slot (thereby reducing the vent’s NFA per linear foot) to accommodate the amount of intake NFA available. Doing this keeps the airflow continuous along the entire horizontal ridge and balanced high and low. As always, be sure the overall amount of ventilation meets code requirements.
4. “If attic access is not practical is there another way to measure the attic square footage?”
Ideally, the attic square footage would be measured at the attic floor length x width (regardless of roof pitch, by the way). If this is not possible, and the homeowner does not have any documentation on file listing attic square footage, you could use the footprint of the house (aerial view of the house) or the number of shingle squares (one shingle square equals 100 square feet) to estimate the attic square footage. Neither of the alternate measuring tactics, however, is as accurate as an attic floor measurement.
5. “How does roof pitch come into play when calculating attic ventilation?”
Current IRC requirements do not factor the role a roof’s pitch plays in the amount of attic ventilation needed, but ventilation manufacturers do. Generally, as the roof pitch increases the volume inside the attic also increases along with the amount of needed attic ventilation. Here’s a rule of thumb to follow:
- Up to 6:12 roof pitch use the standard formula as explained in this article.
- 7:12 to 10:12 roof pitches increase the amount of ventilation by 20 percent.
- 11:12 roof pitch and higher increase the amount of ventilation by 30 percent.
For projects involving vents with motors, the calculation formula is different.
The Ridge Vent Chicken Ladder Hook #11611:
- Works with existing Chicken Ladder system.
- Can clear ridge vent systems.
- Ideal for quick on-and-off work, such as inspections and estimates, solar panel installation and small repairs (masonry, HVAC, roofing).
- Attach ladder section with a 1 1/2-inch bolt and reversible lock nut for safety. (For quick connect, use safety clevis pin.)
- Raised solid-steel rungs are hand-welded for safety.
- Wheels to roll up roof and prevents damaging shingles.
- 250-pound capacity.
- Powder-coated safety yellow.
- Made in the U.S.
The Edge Vent provides 9 square inches of net free area per linear foot to balance with ShingleVent II ridge vents and other Air Vent exhaust vents. The rooftop installation keeps the roofer on the roof. Internal baffles and filter provide weather protection.
The vent is constructed of the same material as industry-trusted ShingleVent II ridge vents. Each 4-foot piece has integrated end plugs on each end. Radius design allows for increased airflow. It features a 3/4-inch low profile and can be used on roofs with a minimum 3:12 slope. Setting tabs on bottom underside assists with installation.
Air Vent offers a limited lifetime warranty and five-year Replacement Plus protection.
CertainTeed Ridge Vent is available in 7, 9 and 12 inches with filtered and unfiltered options. Each ridge vent is made of high quality co-polymer to remain sturdy, nailable and flexible. Reinforced ribs provide greater stability and rigidity, imprinted slot guides ensure proper slot width, and nail holes and nail lines enable easy, mistake-free installation. The product line also includes a Class A fire-rated vent.
CertainTeed Rolled Ridge Vent, also available in filtered and unfiltered, is designed for use in roof pitches from 3/12 to 12/12. The product features a unique, virtually invisible profile that installs fast.
CertainTeed Intake Vent is easily installed on a shingled roof with or without overhangs, and can be used to supplement existing soffit or undereave vents. Internal baffles, drainage system and weather filter provide three levels of weather protection. The intake vent allows air to flow into the attic and helps prevent heat build-up and ice dams.
The new ventilation products feature proven, effective technology for shingle roofs in all climates and come with a lifetime limited warranty and five-year SureStart Protection.
The products are designed with an external baffle to deflect wind and weather over the vent, creating low pressure above the vent to pull air out of the attic. Each vent comes in a black finish to blend with a variety of shingle colors and create a clean, uncluttered roofline. All provide excellent weather protection and prevent premature deterioration of roofing materials by continuously moving air year-round to improve interior comfort.