Venting REMOTE insulated walls
I’ve been looking for a video article I saw in the last (2) months that covered the subject of providing a vent path at both the top and bottom of a wall insulated with rigid insulation at the exterior. The general concept was to place a thin strip of fiber-mesh type material between the 1×4 strapping bays at both the top and bottom. I remember the top end detail but the lower end detail is what I can’t remeber accurately.
If it helps you remember the scene may have been at a Building show and Martin, you may have been interviewing the builder who was discussing the topic generally. The author discussed various products he had used successfully to vent walls in both directions (cora vent plastic stripps with the small holes and cedar breather type type products) but most important to me is the detail at the bottom where blocking behind the water-course board included a provision for air to vent through the fibert-mesh.
i was impressed by the claim that insects were prohibitted from entry by the fiber-mesh and since I consider NH’s annual rainwater to be high and the environment generally wet, I think venting the airspace with openings top and bottom makes sense. I’ve got a project on Lake Sunapee NH nearing this stage of work and am considering revising my top and bottom details to better promote exterior drying of the wall assembly. The siding will be preprimed vertical grain Hemlock clapboards.
Do you recall this article? Can you direct me to it or to a detail for this venting technique?
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Replies
Harry,
I don't think I know what you're looking for. Here are links to two videos showing the installation of exterior rigid foam, but neither video goes into detail about how to install insect mesh at the bottom of the rainscreen gap:
Superinsulating a Home With Rigid Foam
How to Install Rigid Foam Insulation Outside a House
I'll send an e-mail to Rob Wotzak to see if he know about the video you are looking for.
Harry,
There's a chance you may be talking about the first video in the player at the bottom of this page:
Videos on GreenBuildingAdvisor.com (https://www.greenbuildingadvisor.com/new-videos-greenbuildingadvisorcom)
(Scroll down to the bottom of the page to find the screen with this video.)
In the video, builder Mike Guertin and GBA technical director Peter Yost are at a trade show discussing a mock-up of rain-screen siding with various mesh details.
Rob, Thanks, That was it!
Mike Guertin's piece seems to be addressing an issue that needs more discovery and perhaps there is room for a new product or two that will provide and integrated vent material and insect screen. Where he finds enough scrap (Cobra Vent mesh) to do the entire perimeter top and bottom of a project is beyond me. I'm looking for a supplier of a fiber-tech-mesh that maybe can be purchased in strips.
Guertin also uses 3/8 -inch plastic vent battens for nailers where heis encouraging horizontal venting. Has research been done on the holding strenth of such a material with typical clapboards such as Hemlock or other manufactured siding?
Thanks,
hgs
Harry, I'd like to add a few comments to what was presented in that excellent video of the discussion between Mike and Peter. My house (up on Lake Winnipesaukee), has two-foot overhangs, and we don't get too much strong wind, but I still wanted a rainscreen gap behind the siding, which is cedar clapboard. The gap I specified was only 1/4", roughly equivalent to the 7 mm thick version of the Homeslicker product, as compared to the 10 mm version, as would be required in those parts of Canada where rainscreen is code.
For screened venting at the top and bottom, we used Cor-A-Vent S-400 strips. As packaged, those strips are four feet long, 1-1/2" wide by 1" thick, with six layers fastened together to give that inch. We separated the layers and used a single layer. For a rainscreen gap more than my 1/4", two layers could be used. First a narrow strip of insect screening, just a few inches wide, was stapled to the bottom of the sheathing and left to hang down. Next the Cora-A-Vent strips were stapled on over the screening in a continuous row at the bottom of the sheathing. Finally the screening was brought up and over the vent strip and stapled above the strip. The 1/4" wood furring strips, 16" oc over the stud locations, were butted up against the top of the vent strip. This is different from what was shown in the video, where the furring strips appear to be run to the bottom of the sheathing, with short pieces of screened vent strips fit between the furring strips.
At the top of the wall, and below each window, the fastening of screening and vent strip was essentially the same, just upside down. Wood trim was 5/4, to accommodate the slight increase in total siding/rainscreen gap thickness. At the tops of wall sections and under windows, the trim was rabbeted to provide an exit path for air flowing up through the vent strip.
I must thank Mr. Seidel and Mr. Russell for posting regarding using Cor-A-Vent for the rainscreen. I knew about their products for roof venting, but never considered that they may have one for rainscreens. They have a product available in 7/16" and 3/4" specifically for this use, including an "enhanced insect screen" attached. The only problem is that it is a little pricy at about $1.30/foot for the 3/4" product.