Painlessly Complying with Code-Mandated Air Sealing

Last updated on April 6th, 2023 | By Matt Risinger | No comments

Blower door test on Matt Risinger project — The energy code now requires most builders to meet a maximum 3 ACH50 score on a blower test. This can be a painful number for a builder who hasn’t been purposely air-sealing the building in the past. But it doesn’t have to be as painful a learning curve as it was for me.

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.

Air sealing from the interior and exterior door frame — *Air sealing from the interior is fairly easy, but it’s not as effective as air sealing on the exterior, at the source of the air flow.*

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.

Interior view of Matt Risinger project getting an effective air seal and water barrier at the same time. — Good-quality tape can effectively seal sheathing seams, but it be labor-intensive if you are doing it just to add an air seal. It is much better to put added effort into getting an effective air seal and water barrier at the same time.

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.

peel-and-stick housewrap DELTA-VENT SA — A peel-and-stick house wrap will reliably seal the majority of wall leaks, as long as you also address the foundation-to-wall connection, and interior air seals at window sills where you need to keep the flashing/air barrier open to allow for drainage. Once the walls are sealed, you can focus on penetrations through the lid.

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.

Close up image of DELTA®-VENT SA vapor permeable air- and water resistive barrier and DELTA-MULTI-BAND — DELTA®MULTI BAND is one way to form an effective air seal between the foundation and the wall. DELTA®MULTI BAND comes in two widths—60mm (2.36 inches) and 100mm (3.94 inches). On the concrete, you need to apply a primer first. Shown here we have a board-form concrete foundation that will be left exposed, so we first rolled out painter’s tape before applying the primer, so that we would have a clean edge that won’t show once the cladding is installed.

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.