Vents To Hold Down Membrane???

tekwrytr

Has anyone heard of (or, better yet, used) vents to "hold down" free floating membrane roofs? Best description I have heard is that they are some kind of reverse-draft vents that work the opposite of rotary turbines. In short, rather than allowing warm air to go up, the vents are supposed to hold the roof membrane in place.

The claim is that they eliminate the need for other fasteners or adhesives when installing EPDM, TPO, etc. membranes over non-nailable decks. Any information or referrals would be greatly appreciated!
Thanks

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johnk

http://www.designbuild-network.com/c...erials/protan/ there is some info on here,go down about 3 paragraphs.

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tekwrytr

Thanks! This is exactly what I was looking for!
Thanks, again!

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tekwrytr

Has anyone actually used these vents to hold down EPDM or TPO membrane? They are apparently used extensively in Europe, but that doesn't mean much (different building codes, for example).

The theory is sound. Just as hurricane damage to roofs can be diminished by opening windows (to equalize the air pressure and diminish the uplift of low-pressure area over the roof surface), so would vents diminish the effect of wind uplift. The problem is that this is a roof, not a classroom discussion of physics. Sometimes things don't work in the real world as well as the theory indicates they might.

Has anyone on this forum ever actually used these vents as an alternative to ballast, mechanically-fastened, or fully-adhered EPDM installation? Or heard of anyone in the US or Canada who did?
Thanks

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Commercial EPDM Rubber Roof Repair - Maintenance - Re-Roofing Exclusively. Serving the Twin Cities, MN Metro area since 2001.
http://www.tekwrytrs.com/roofing/

Gilby

I have used some thing very similar and except on ours we heat weld them on and they are not fastened to the roof they are made to float. So they can vent the roof properly. I am not sure how well they will work if you fasten them down.

tekwrytr

Understood. They would have to float with the membrane, rather than being fastened to the roof. As I understand it, the basic principle is that as soon as the membrane starts to lift, the pressure differential equalizes on top of, and underneath the membrane, essentially preventing the lift effect of the lower air pressure over the membrane.

Any idea what kind of area is handled by what size vents? The actual vents don't seem all that important, as long as a water-tight seal can be maintained, they can be stuck to the top of the membrane and float with it, and have sufficient air flow to eliminate uplift.
Thanks

__________________
Commercial EPDM Rubber Roof Repair - Maintenance - Re-Roofing Exclusively. Serving the Twin Cities, MN Metro area since 2001.
http://www.tekwrytrs.com/roofing/

Gilby

It is code for us to install one two way breather vent per 1,000 square feet. The vents also help draw out the moisture from underneath the roof. I have never fastened them down. I can show you pictures of the vents we use if it will help

rwolfe

The product that you're enquiring about is Kelley 2001 roof systems. The technology behind the system is when the wind blows harder, the vents put more pressure to the underlying substrate. The vents act as a vacuum. But it takes wind to make this happen. I do work in Broward and Dade Counties here in florida. Although the roof is proven to work, they cannot pass any testing in dade county. Sure Kelly has noa's but none involve the vents. I've installed the system on a number of Seminole County School projects with reasonable success. They utilize (or used to at least) carlisles membranes and accessories. However they also have a modified line from what I understand. I would ask whether you are looking to use this on a project. If so, I would recommend talking to the Kelly guys because the system relies heavily on proper details being used. You must create an airtite seal at all perimeters and penetrations. Interesting product and easy to install. Fast too.

Hope this helps.

Ed the Roofer

rwolfe is correct.

One other point about the Kelly System, is that the building has to be completely air-tight.

What good would it do to have the pressure holding down the roof, when multiple dock doors were opened, neutralizing the pressure?

Ed

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apehangeralfy

The building doesn't have to be airtight, just the deck. It's best used over a concrete deck, the ends are secured with specific "rope" tape and termination bars or plywood and all penetrations are picture-framed with the same to seal off the edges and such... Only the field actually floats....

I have done a few. They work great for the most part. I've seen one in 65MPH+ winds and it held tight (it is over 500 square) The only issue I have is the fact that is is essentially a vacuum under the membrane and if it gets just a pin hole in it at a point that is under water (during a rain, near the drain...), the water has the added pressure of the vacuum pulling the water in, a pin hole in a bad spot can cause a major leak.