Intello as an air barrier?
joenorm
| Posted in General Questions on
Im curious if Intello smart vapor barrier is worth the extra cost for a full interior air seal?
Climate 4C Marine.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
"...worth the extra cost..." is subjective.
Of Course, I figured i'd get that response after I wrote it.
Is there a cheaper option that works just as well? For example, well detailed drywall?
Or is Intello all its cracked up to be? It actually looks pretty slick if blown in cellulose is planned, to get a continuous interior air barrier from ceiling into walls.
Certainteed MemBrain (2 mil nylon) is substantially cheaper than Intello, but can't be used as blowing mesh. With the mesh rolled flat to the stud edges it can be applied to the interior and detailed as an air barrier prior to putting up the drywall.
Whether the labor of the additional step & material cost of the mesh adds up to more than Intello depends.
Is this new construction or a retrofit?
In new construction detailing your sheathing as your air barrier is the typical best practice, and in climate zone 4c, if you use a rainscreen (or other vented cladding) you only need a class III vapor retarder (such as latex paint), so Intello seems a bit overkill from both an air-tightness and a vapor control perspective.
But in an interior retrofit, you probably don't have airtight sheathing, and if you don't have vented cladding and need a type II vapor retarder anyways, then there's potentially more of an argument that Intello or similar should be one of the options you consider.
Is your builder familiar with fancy membranes, airtight drywall, etc? Always worth asking them what they prefer (and why).
IF you need both a "smart" vapor retarder (SVR; translation: variable vapor permeability with different moisture content) and an air barrier in a sheet good, Intello wins hands-down for me because it is tough. Membrain is very hard to detail properly as both an SVR and air barrier, simply because it is only 2-mil (that is 2/1000 of an inch) polyamide with no reinforcing.
Just depends on what you are asking of the material.
Peter
>"IF you need both a "smart" vapor retarder..."
In zone 4C a smart vapor retarder isn't necessary as long as the siding is back ventilated, or if there is exterior insulation, sufficient exterior R.
>"Membrain is very hard to detail properly as both an SVR and air barrier, simply because it is only 2-mil (that is 2/1000 of an inch) polyamide with no reinforcing."
Though I'd never use it as the primary air barrier (wouldn't use Intello as the primary air barrier either), but in my limited experience detailing MemBrain as an air barrier would not fall under " ...very hard to detail properly...", or even "kinda hard", not significantly different from detailing 4 mil polyethylene vapor barriers as an air barrier (perhaps the most commonly used approach by production builders in my area.)
Detailing the structural sheathing as the primary air barrier is usually the most robust solution.
Zone 5 - We are building a double stud wall assembly to be filled with dense pack cellulose. 9" walls and 16" beam roof with over roof. The primary air barrier was supposed to be Siga majvest on the exterior of the sheathing - but the installation is not consistent and sometimes transitions to tapes, and sometimes to taped plywood which makes me suspect of its ultimate effectiveness. (see RO flashing pic) I requested a smart vapor retarder on the inside because I worry about humidity in the walls (I will have furring rain screen on the exterior with LP Smartside siding. The builder is telling me that there is no need to tape the smart vb (either siga or intello) because we are 'only using it as a vapor retarder.' I think that the intello must be taped even if we only care about the vapor issues - because moisture follows air and air will find its way through the seams. Wondering what the experts think. Thanks
Useful info
We have used Intello as a primary AB and it performed very well. Installation is where this membrane really shines, it’s robust and the Vana tape that is recommended makes for a very tight assembly.
We have also used Certainteed’s Membrain but it’s pretty miserable to work with. In fact we used both Intello and Membrain on the same project. During our pre-drywall blower door test (depressurization), both membranes were being pulled in considerably by the air pressure, while the Intello held up just fine, the Membrain actually pull through our staples in some spots and had to be repaired.
There is a cost increase with material like Intello or Siga Majrex compared to Membrain but like many things, you get what you pay for.
If one is using blow in fiberglass or cellulose insulation in the walls, do folks normally use Intello as the netting for the blow in, and just tape up the holes?
I am in Zone 4c, about to start rough in and am on the fence of spending the extra money on interior air barrier. I already have Mento 1000 on the exterior, transitioning to DB+ at the ceiling/attic plane. I am leaning toward Airtight Drywall Approach (sealed electrical, sill foam at top and bottom of drywall/wall seam) with latex paint.