Painlessly Complying with Code-Mandated Air Sealing
When I first started doing blower door tests 15 years ago, I was full of bravado, thinking I had a pretty tight house. I was using a good house wrap and taping the seams, and I was paying my insulation and drywall contractor extra to include “air-sealing measures.” I thought “No problem. I should be good,” right? No, I was severely disappointed. My first blower-door scores were in the 6 to 7 ACH50 range. This means that when the house was depressurized to 50 Pascals, I was moving air at a rate 6 or 7 times the enclosed volume of the house every hour. I wasn’t anywhere near a tight house.
Fast-forward a couple years; I thought I had found the answer in the spray foam. All the hype led me to believe that with a fully spray-foamed envelope, including a spray-foamed attic and sitting of a slab-on-grade foundation, I’d be good to go. I spent a lot of money doing it this way, but again I was totally disappointed with the result. Some of my first homes done this way were in the range of 3 to 4 ACH50, or sometimes even above 4. Certainly this was tighter, but it was not anywhere near as tight as I thought it would be given the marketing hype surrounding both open- and closed-cell spray foam.
Note all this was all before building codes forced me to pay attention to air-sealing limits. I was driven to tightening the shell mostly by client demand on the architect-designed homes I was building in the Austin market. So I kept pushing for something tighter and looked to other methods to seal up all the holes in the building shell.
I used some interior caulking. I used exterior caulk, including acoustical sealant. I began experimenting with a variety of tapes to seal the seams on my plywood sheathing.
At that time, I was still relying on standard house wraps that we stapled on. Sealants were helping a little bit, but I still was not getting what I wanted in the way of a tight house.
It wasn’t long after this that I started using peel-and-stick water-resistive barriers– specifically DELTA®- VENT SA and one or two others on the market at the time. With a peel-and-stick WRB, combined with the other air sealing methods that I had come to, I was able to consistently score under 2.0 ACH50 on blower door tests.
Really, what the peel-and-stick gave me was peace of mind. For the first time, I was able to get reliably tight walls. Regardless of the pressure conditions inside and outside the house, all my sheathing joints, all the plate lines, and all the gaps in my rim joists were sealed tight. Having the house wrap bonded securely to the sheathing means it isn’t going to flap around, or get buffeted by the wind and loosen up before the siding goes on. It also means that air pressure differentials – either from indoor mechanicals or from exterior wind – won’t cause the house wrap to balloon outwards at sheathing seams or other cracks and gaps in the wall framing. Loose-applied house wraps are pretty good at blocking air when the house is depressurized, but not so good when the house is positively pressurized.
With the walls sealed, all I had to worry about were the penetrations. The big ones are through either my roof, or through my ceiling plane. (Granted, there are a lot of these, but when I’m not having to deal with so many air leaks in other locations, I have the bandwidth to focus on them.) And, because I’m still doing mostly slab-on-grade, I still have to do a super good job of sealing my walls to my foundation.
Energy Codes Today
These days of course, the building code is asking most builders to blower test their houses for the first time and get to that minimum 3 ACH50 threshold. (If you’re not familiar with this process, be sure to watch the video below for an overview on blower door testing.)
Note, also: the performance method for code compliance will give you the most flexibility for choosing systems in the home that you and your clients want. When you choose a performance path, it often makes sense to get the house even tighter than the 3 ACH50 maximum. The tighter it is, the more you can back off on some of the other requirements, which can be helpful if certain systems have been specified for your build that wouldn’t allow you to comply otherwise. These days the code offers a lot of flexibility, as long as you meet mandatory measures and can verify performance.
If you’re not familiar with meeting today’s more stringent energy requirements, don’t worry. You can to forego all the pain that I went through and get a really tight shell by focusing your air-sealing primarily on the exterior. That’s where the peel-and-stick house wraps come in. Once you got the walls sealed, you’re dealing primarily with two things: the lid and the wall-to-foundation connection.
About Matt Risinger, CEO & Chief Builder at Risinger & Co.:
Upon graduating from Grove City College in Pennsylvania with a degree in Industrial Management, Matt began his construction career at NVR in Washington DC.
In 2005 Matt and his growing family relocated to Austin where he started Risinger & Company. Matt is dedicated to Building Science and is a recognized expert & thought leader in the industry.
He also has a large following on his YouTube channel, where you can find videos on installation techniques, product reviews, and everything in between. You can find additional details on Matt on our About the Blog page.