Walls That Can Breathe Are Walls That Can Dry

November 10, 2018



Walls that can't dry will rot


In recent years, moisture management has become a very hot topic among the building science community, especially related to siding and insulation on the exterior walls.

If moisture gets trapped in the walls of a home, it can generate mold and mildew, unhealthy conditions for the people that live there, or even compromise structural integrity of the home. On top of all that, it can actually leave you open to a lot of liability if you do not take steps to effectively manage moisture and prevent these types of problems.

Ben Franklin said, "An ounce of prevention is worth a pound of cure," and mold growth is the perfect example of that principle because when you install new siding, it's a no-brainer to add continuous insulation. What I mean by that is even if you don't add new insulation, you're still gonna pay for it, and then some. So just do it.

But when you add new insulation, take measures to prevent moisture damage.


People produce a lot of moisture

So to demonstrate one critical prevention measure, I'm gonna ask for some help for my man Mike. Come on in here Mike, let's get this stay-dry glove on your hand. Alright, thanks.

The average family of four generates 4 to 6 gallons of water vapor indoors every day from cooking, cleaning, and even just breathing. Adding rigid continuous insulation to a home tightens the building envelope to reduce energy loss, but when you do that, you can also create problems if the home is so tight that moisture can't escape through the walls. Let the walls breathe.

So let's take a look at our demonstration now. Remember that breathability is measured by a high permeability. You need perm rating higher than 2 to be confident that your walls are actually breathing. So this plastic bag is a very low perm rating, similar to some other products. As you can see, his hand has already generated moisture that's getting trapped inside the bag.


Walls should allow drying to the inside, the outside, or both

With this much moisture generated in such a short time, you can imagine how important moisture management is in a tight home. That is why Progressive Foam's premium fan fold and insulating sheeting products are now made with something called the "stay-dry technology."

It is a proprietary manufacturing process that makes insulation three times more breathable than comparable products. They work similar to Gore-tex, actually, keeping bulk liquid water like rain away from the wall but still allowing water vapor to pass through the material and escape to the outside. This protects the home and the people living in it from potentially dangerous moisture buildup.

So remember two things. One, insulation is a no-brainer on a siding job, and two, permeability is a key to preventing mold growth. In order to know that you're using the right insulation on a siding job, ask for progressive foam and look for the new stay-dry technology on fan fold and sheeting products. 


—This video is from Progressive Foam Technologies, one of ProTradeCraft's advertisers. Founded in 1992, Progressive Foam invented and brought insulated vinyl siding to the marketplace and have since diversified to add siding insulation products that can be paired with fiber cement, engineered wood, steel, and others. See all of Progressive Foam Technology's videos.