Metal angle/drip edge under exterior rigid foam
user-3122620
| Posted in Green Building Techniques on
I’ll see if I can word this question correctly.
Wall Assembly is the following:
2×6 stud
3/4 plywood
1.5″ XPS foam
3/4 furring strip / ventilated rain screen assembly
Hardi Plank Siding
I see a lot of details in my research for exterior foam and ventilated rain screen assemblies that include a field formed metal angle around the bottom edge to protect the bottom of the foam and direct any water away from the house.
How much space should I leave between the metal angle and the bottom of the assembly to allow for ventilation air?
Is the protection mainly for insects or does the foam want to be protected from the weather, or both?
Thanks,
Kevin
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Replies
Kevin,
There are lots of ways to trim out this area.
You may be conflating two different components: (1) Metal flashing to protect the bottom of the rigid foam, and (2) Insect screening or "Cobra-Vent" type material between the furring strips.
For more information on different ways to detail the bottom of a ventilated rainscreen gap, see this article: All About Rainscreens.
I hadn't looked at that link for several years. It's a great comprehensive guide to rain screens.
Thanks, Martin. That article is one of my favorites and I actually used it to help my contractor understand what we were doing with the rainscreen.
we are installing cora-vent SV5 at the bottom and top of my rainscreen, so that will provide my insect screening. I am installing the metal angle at the bottom primarily to cover and protect the bottom of the foam, but I wasn't sure if I should extend it proud of the siding or just end it at the edge of the foam. If it extends an inch or so beyond the siding i dont want to block off the cora vent so I was curious how much of a gap would be appropriate not to stifle ventilation air from entering. I as thinking about an inch gap.
Thanks again.
Kevin
Kevin,
For more information on installing flashing to protect the bottom of the rigid foam, I suggest that you check out this video: How to Install Rigid Foam Insulation Outside a House. (See the screen grab below.)
You may also be interested in the information in this article: How to Install Rigid Foam Sheathing.
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Kevin,
If the flashing is solid there's not much point in extending it beyond the foam, which leaves the cavity open for ventilation. If you want to extend the flashing right out to the siding I'd use U-shaped perforated stock and then you can forgo the Cor-A- Vent.