Bug screen material recommendations?
hertzr
| Posted in General Questions on
Good morning,
I am planning for new siding that will incorporate 4-in of exterior rigid insulation and a rain screen. Am curious of what materials people recommend for the bug screen at the bottom of the furring strips.
I’ve seen mesh ridge vent materials and stainless/metal wire mesh; any others? Thanks,
Richard
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Replies
The foam-type ridge vent material is popular. There is also a formed perforated metal strip intended for this purpose. Lots of people like coravent too (kinda like plastic cardboard strips).
If you use metal mesh screen, I recommend you use stainless steel screen and not aluminum. Aluminum screen is too prone to rotting away if any wet debris accumulates and sits on it.
Bill
https://www.menzies-metal.com/metal-flashings/perforated-l-channel-rain-screen-high-back/
Thanks Malcolm, that’s the strip I was talking about. I couldn’t remember the manufacture or product name. I think there is another version out there that is a bit of a “C” profile instead of an “L”. The C profile would probably be better.
Bill
Bill,
I linked to the wrong one: https://www.menzies-metal.com/metal-flashings/perforated-j-channel-rain-screen-low-back-5-lengths/
We are lucky in that all our lumberyards here stock the J trim and can custom bend any profile to cover various thicknesses of foam. The j (or C) profile is a lot easier to use in that you can set your battens in the bottom as you install them.
I imagine in places where this is unavailable getting a metal shop to bend any perforated stock - say that used of soffits or vents - would also work.
Malcolm,
Found the j trim here: https://www.menzies-metal.com/metal-flashings/perforated-j-channel-rain-screen-low-back/
Was looking at this: https://www.advancedbuildingproducts.com/wp-content/uploads/2018/04/Watairvent-Furring-Strip-Brochure-PDF.pdf
as an all-in-one (furring strip and bug screen) solution but was worried bugs can get through the holes in the Watairvent.
However, the holes in the J channel you shared look to be about the same size, so I guess the Watairvent gaps are OK(?).
Thanks!
Ronnie + Sandy
Ronnie & Sandy,
My purely anecdotal experience is that insects that can make it through the 1/8" holes can also find their way into the cavity (and your house) some other way.
I have a friend who is a builder on the Canadian prairies, who found the bottom of his rain-screen cavity, which was protected by insect screen, was almost filled with the carcasses of ladybugs. Short of building a house like a boat, some infestations are pretty much unstoppable.
Hey Richard.
A lot of builders use common window screen material because it is affordable and easy to wrap around the bottom of the furring strips for an efficient install. Along with Coravent products and the metal channel that Bill and Malcolm recommended, you can use a roll-out ridge vent product like Cobra Vent. It was recommended to me when I was installing siding a few years ago and it was affordable, easy to install, and seemed to do the trick over time.
Brian,
The main reason bug-screen and mesh products fell out of use here in BC was their susceptibility to mechanical damage (mainly from vegetation growing into the base of the cavity), and the difficulty of repairing them once it had occurred.
Looking back, the same happened with soffit ventilation. Old issues of FHB show details with bug-screen, and I remember seeing it on cottages in the 70's, but for the same reasons it was abandoned in favour of more robust materials.
Aluminum insect screen is also prone to rotting out if any wet debris (like plant debris) sits on it for any length of time. Fiberglass screen would be better, but since it won’t hold bends, I suspect it would be a huge pain to work with.
I wouldn’t use insect screen material on a rain screen myself since it’s not very durable. There are better options available.
Bill
Another potential problem with rain-screens as narrow as 3/4" is rodent entry. Any insect screen needs to be tough enough to repel them, or have some back-up material that will.
Good point. You can get fine mesh stainless steel hardware cloth which would be a much better choice. I’ve used this material to make rodent barriers in vent pipes and drain lines before.
Bill
Malcolm and Bill,
I haven't hear that feedback about the screen, but it makes sense. I'll check in with some builders who I know are executing these details regularly and see if any of them have moved away from screen and if so, what they have switched to.
Brian,
That would be interesting - although to the best of my knowledge BC is the only jurisdiction to mandate wall cavities in its codes for all residential structures in the coastal area - and probably represents over 90% of the rain-screens being built in north America. That doesn't mean we have a monopoly on good practice, but it's probably worth looking at the experience of builders here rather than the one-off builds among those near you. With the best of intentions FHB and GBA does tend to favour what's happening in New England.
I can't argue with that, Malcolm. I'm going to connect with you off of the forum. Maybe you can help me find some qualified sources out your way.
I completely agree with Malcolm with one exception: Many builders will never see those rainscreen details again unless there is a catastrophic failure of the siding. They might not know that what they're doing doesn't last.
I usually get called in to consult on strange problems down the road (albeit usually in commercial sites), so I'm used to thinking about things that might degrade and fail in the future Many builders don't see what they've built again years in the future. It might be good to check with home inspectors and/or contractors specializing in resides to see what they've found with systems that have been up at least a few years.
Regarding the use of the regular aluminum mesh insect screen, Malcolm's concern was with rodents while my concern is with long-term (years) durability of the system in the elements. I like to build things that last.
Bill
That's a good point Bill, one that I often wonder about when I see people giving advice on products and practices. When it comes to products and assemblies, meeting codes and voluntary standards is one thing, easy of installation is another. Judging durability and longevity require that projects be revisited, again and again, for a long time.
I bought a fine mesh stainless steel wire cloth from Darby Metals a couple weeks ago; ordered it slit to 3-3/4" wide so it can fold under the foam and rain screen material. It's pretty stiff, so shaping 300 linear feet of it will be annoying but at the end of the work should last a good long time.
Some sheet metal fab shops can roll form material like this. The machine is similar to what they use to make continuous aluminum gutters.
Another option, and probably the better option, is to cut the material into 8 or 10 foot strips and form it in a bending brake. This will give you manageable size pieces to work with in the field. Trying to install a continuous piece is asking for trouble — you’re going to have bends and defects as you go and probably a lot of wasted time.
Bill
What do you guys think of galvanized steel bug screen like this one: https://www.wholesalescreensandglass.com/Phifer_Galvanized_Insect_Screen.html
Vlad,
For me the question isn't which bug-screen performs best, it's whether it is the appropriate material to use at all. (See the discussion above)
Malcolm,
I agree that perforated metal J or L channel is the best option, but I am having hard time sourcing reasonably priced stock. Maybe I should make a trip to your part of the woods and get the right stuff.
Vlad,
In the absence of a reasonable alternative, use the best screen you can (which as Bill points out is stainless steel), install it as smoothly as possible to avoid gaps, and keep planting that may infiltrate the cavity away from the base of your foundation.
To be fair, bug screen was used here for many years before being superseded by perforated stock, and in most cases worked just fine.
I would only use stainless steel mesh. Galvanized and aluminum screen are both prone to rotting out when wet yard debris sit on them for any length of time.
I also agree with Malcolm, regular insect screen really isn’t the best product to use here. If you want to use screen, at least use stainless hardware cloth with heavier mesh.
Bill
Vlad, if termites are a consideration where you are building, this is worth a look. Or search for the information the Termimesh people publish regarding maximum opening size for a termite screen.
http://www.wovenwire.com/termite-mesh.htm