IN-Vent vs. SmartVent

by steve • June 16, 2009
(From March 2007)

Now that you've read about IN-Vent, the on-the-rooftop intake vent that lets fresh air in when soffits are out, let's get down to brass tacks: How good is IN-Vent and how does it stack up to the competition?

Let's start with the competition, or more specifically, DCI Product's SmartVent. Like the IN-Vent, SmartVent is made from corrugated plastic sheets, has a filter to keep rain & snow out and installs essentially the same way. But when it comes to performance and quality of material, that's where the similarities end. For this comparison, we'll link to the SmartVent website to make it easy for you to see what they show.

Let's start with the most important feature of any vent - the vent itself, or the airflow it allows. SmartVent claims 9 square inches of Net Free Vent Area (NFVA) per lineal ft., but that's questionable and here's why. The leading edge of the SmartVent is four plys thick of their sheet plastic, and those four plys might provide 9" of NFVA, but the air entering the roof through SmartVent actually only passes through three of those plys. If you look at the SmartVent installation instructions, you'll see that the product transitions back to three plys, then two plys, then one as it tapers back into the roof deck. The slot cut into the roof deck to allow the air into the attic is positioned just behind the section of SmartVent where it transitions to three plys. What does that mean? Simply, it means that, despite the four plys at the leading edge, only 75% of that air can pass into the attic because of the positioning of the slot in the deck.

Then there's the fabric filter SmartVent uses to keep weather out. This one is actually pretty easy - compare and contrast their filter (top) and ours (bottom). IN-Vent's openings are clearly visible through the air-permeable material, which is black to blend in better with the roof than SmartVent's lighter gray material.
To compare the two products, apples to apples, Cor-A-Vent ran an airflow test to see how much actual air passes through them. As an aside regarding the test, it's run on a hermetically sealed roof section, where the only place the air can flow through is the hole in the deck and the vent over it. The test measures the amount of air in cubic feet per minute (CFMs) at 5, 10, and 25 pascals of pressure. It's the same test we used a few years ago to test the ridge vents out in the marketplace - check the link to read more about the procedures. The same test was seperately repeated by another ventilation manufacturer, Headrick Building Products, which has since been bought by GAF. As a result, the Headrick website and a wealth of airflow information no longer exists on the Internet (but that's a story for another day).

IN-Vent will provide 6.75 sq. inches of NFVA per foot, and 13.5" per ft. if installed on both sides of the roof. Again, SmartVent claims 9" per ft. on one side and 18" for both sides. As for the airflow test results, let's go to the scorecards:

- IN-Vent airflow @ 5 pascals (pa) of pressure: 57 CFMs

- SmartVent airflow @ 5 pa: 21 CFMs

- IN-Vent @ 10 pa: 96 CFMs

- SmartVent @ 10 pa: 40 CFMs

- IN-Vent @ 25 pa: 170 CFMs

- SmartVent @ 25 pa: 80 CFMs

More than twice the airflow. Despite the claims SmartVent makes, it's easy to see which product will actually vent more air, and balanced intake ventilation is the most important aspect of any attic vent system.

IN-Vent is made from 1/4"-thick profile-extruded polypropylene plastic sheets, so the openings are roughly twice the size as SmartVent's. The plastic is very rigid and has a third ply on top that does not vent, but provides rigidity so IN-Vent won't smash down when you nail it on. IN-Vent also comes with two 12"-square End Cap sections that are coated with a UV inhibitor so they'll stand up to the sunlight, and their black color will blend in better with the roof. SmartVent's end caps? More of their light-gray filter material.

It's pretty clear that IN-Vent is the best choice for on-the-roof intake ventilation when you can't (or don't want to) access your soffits. Call us at (800) 837-8368 or shoot us an email if you have any questions about IN-Vent.