Wrb detail options for zone 6
A_mocko
| Posted in General Questions on
I am currently self building a house in zone 6 NW Montana and I’m in the stages of trying to figure out the best wall assembly that is within my budget. I have 2×6 16” walls and plan to do fiberglass insulation with vertical classic ribbed metal siding. My question is what is my best option for wrb and rain screen. My budget limits me to not being able to use exterior Insulation so I know I will get some condensation built up on the walls from the metal siding. Hydrogap SA seems rather expensive so just wondering what budget friendly options there are out there? Thank you.
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Replies
Leaving aside energy implications etc. of your wall plan, I would not lean toward hydrogap as the first option as the space is so small. (Incidentally Tamko makes a slightly cheaper version depending on dealer pricing.)
We usually use a drain mesh product such as home slicker or its competitors. But we're paying for labor and it makes sense to use an expensive product that saves on labor.
You may find that something simple like strips of corrugated plastic (buy full sheets and rip them down https://www.homedepot.com/p/Coroplast-48-in-x-96-in-x-0-157-in-4mm-Black-Corrugated-Twinwall-Plastic-Sheet-10-Pack-COR4896-BK/205051024) or even just wood strips (hoping that the air/drainage at the ribs is adequate) would require the least cash input, even if they take a bit more time.
A_mocko,
The gold standard would be horizontal strips of Cor-a-Vent every 32". If you are considering a dimpled or mesh WRB, make sure you use a perforated flashing at the base of the siding to allow some airflow.
I am leaning towards either coravent or diy firring strips for rain screen. Does it make since to go with a self adhered wrb like Henry blue skin or something similar or is your standard tyvek efficient for this wall assembly with maintaining a vapor open exterior wall assembly?
A-Mocko,
Because the siding has it's own drainage gaps, another option is just wood strapping with a tapered top edge.
A self-adhered WRB makes sense if you want to use it as an air-barrier. If that is somewhere else my preference is Tyvek Commercial, which is a lot stronger than regular Tyvek, but still very vapour-open.
You want self adhered when you are dealing with something like board or T&G sheathing. The peel and stick is about the only reliable way to get a solid air barrier with something like that.
If you are starting with OSB or CDX, it is pretty simple to tape the seams with a quality tape for a solid air barrier and use regular house wrap over it. No need for full peel and stick.
As for the siding, I'm with Malcom, since vertical grooved siding is self venting, I would install horizonal wood strapping and call it a day.
If you want higher a higher R value wall that won't cost a lot more, you can go for 2x8 24" OC. About the same lumber cost and slight extra for the 2x8 batts but you end up with a ~25% higher assembly R value.