Does anyone know what this WRB looking green foam is? (picture attached)
I’m re-siding a 100+ year old home. I was planning to put a WRB in, as the house is usually cold when the wind picks up, but it seems like someone installed some sort of thin green foam under the siding (see picture.) Anyone know what this stuff is?
I’m considering removing it and replacing it with Tyvek because this home currently has a mold problem on the exterior facing walls and if water can’t escape the building envelope, because the green foam doesn’t allow for vapor exchange, that might explain why. My understanding is that new homes are designed to account for water vapor issues but this place was not built that way.
The exterior walls are sheathed with 2 layers of ~9/16″ ship lap, then the green foam and then the old clap board that I’m replacing with hardie plank.
What are your thoughts? Could the green foam have changed the building ventilation properties such that water is now being trapped in the wall cavities leading to interior mold or is that unlikely for some reason? If the green foam may be causing condensation inside wall cavities is there any reason not to replace it with tyvek or some other WRB that allows for vapor exchange?
Thanks for reading.
Looks like thin foam board to me.
Perhaps an earlier version of this, or similar product, (before they figured out it needed perforation to let water escape)
Good plan to remove and replace.
moisture in walls would seem to call for an interior vapor control layer, as well as allowing water vapor to exit the outside.
Like unclemike said, looks to be green fandfold. It’s often used to “flatten” a wall when siding over existing siding, and it looks like that might have been what happened here. It does have a tiny bit of insulation value and could add some water resistivity, but that’s not its primary function.