When it comes to a house, there are four main control layers that you want to deal with. They are (in order of generally accepted importance) water, air, vapor, and temperature. Buckle up for a long post, as we take a quick look at each one of them, and see how we are addressing them in our home build.

WATER
Water is by far the worst of the control layers as far as the amount of damage that it can do, and in an often very short amount of time if not noticed or caught. Think about if you’ve ever had a dishwasher leak, or a pipe freeze. You know first hand the dangers of water. The nice part about those things is that you can often see that very quickly and take care of it, which helps reduce the amount of damage from it. Now take the idea of water, and move it to the outside of your house. Suppose you had a small leak at the top of your living room window where it was improperly attached to the house behind the siding. Every time you had a driving rain, a small amount of water might sneak up behind the siding, and leak down. As it runs down the outside of the wall behind your siding, it finds that small hole, and leaks in. Now, it’s running down inside between the window and the window sill at which point it could run in behind the drywall and you’d never know until you possibly had mold that started to grow.

Obviously that’s a worst case scenario, but it can happen, and does happen. In our house, we are using a product by Huber Engineered Woods called Zip-R (more on the R part below.) On the outside of a normal house, you have OSB or plywood that is then covered in some sort of house-wrap, which you might have heard referred to as Tyvek as they are one of the largest providers of it in the building industry. You put on the house-wrap because by it’s nature, plywood and OSB aren’t great water barriers as they can absorb water that’s against it over time. On our house, our Zip sheathing will act as the water barrier. It has a coating applied to it that seals the OSB and makes it a water barrier.

AIR
While water causes the most damage, even if you can’t see it, air is the one that you can often feel and notice. Have you ever been in an old house in the winter and didn’t want to sit by the window or door because you could feel the cold air seeping in? That’s a draft and a breakdown in your air barrier. Now, some of it could be down to old windows which didn’t seal well anymore, but it could just as easily be air that was seeping through a gap in the house-wrap and finding it’s way in along the edge of where the window or door is mounted to the outside of the house. The house-wrap on other homes acts as the air barrier in addition to the water barrier. Have you ever driven by a home under construction and seen the house-wrap flapping in the wind because there was a storm or something and it pulled through the staples that attached it and it was now flapping all over? The only way to truly fix that would be to re-staple it, and then you should technically tape over each of those small tears in it to restore it’s effectiveness. You can see how that might be a challenge to do.

In our home, the coating that is on the Zip panels is the water and air barrier as well, but it’s a coating that is applied in factory conditions and means while it’s still possible to damage it (for example you bang a hole in a panel on the site or something like that), it’s far less likely. it’s also easier to maintain a perfect air barrier. What about seams, you might ask? When you do a house-wrap, you overlap the rolls from bottom to top, so water runs off and when you overlap them, you keep your air barrier there as well. With the Zip system, you tape all of the seams and joints using their special flashing tape called Zip tape. It is made with an advanced acrylic adhesion specially designed to work with the coatings on their panels. After you apply it, you roll it with a hard roller. When you do that, it “activates” the tape and it forms a permanent bond to the Zip panels. They also make a stretch version of it that you can use in tricky places such as window sills and door openings to get into the corners better.

The old adage used to be that air leakage in a house was okay, it allowed the house to breath. It gave you some fresh air. The only downside to that logic of thinking is that while you got some fresh air in, it also brought with it all the pollen that was in the air, and the air pollution, or wild fire smoke in the air, etc. A much better way to think about it is “build tight, ventilate right.” Many building science folks have said that quote and it’s completely right. I want fresh air in my house, (who doesn’t), but I want to decide how it comes in, and I want to control it and condition it before I have to breath it.

CONCLUSION
I was going to keep going, but noticed this post was getting really long…so I’m splitting it into two instead. So, tune in tomorrow, for the exciting conclusion!