Taping Exterior Sheathing Seams for Better Air Control
Originally published by: Journal of Light Construction — January 5, 2014
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There are 4 things every house needs to control (in order of importance):
The building codes have dictated the Thermal/Vapor Control that builders must adhere to, and nearly every builder in the US knows off the top of their head the R-value of the insulation in their walls/attics. But, until recently the building codes haven't addressed air control. The 2012 IRC now dictates that builders in my climate zone need to achieve a Blower Door test of 5ACH50 which is actually pretty tight and will make quite a few builders need to research air sealing methods in order to truly reach this level of air-tightness. As an aside, it's interesting that codes barely touch on water control which is of course the most important control layer on any house. What difference does it make what R-value your wall has if water is getting into that wall through a leaky window, or a poorly sealed plumbing or hvac penetration?
So, in my quest to build ever tighter houses I've decided that my goal is for every house I build to get as close to 1ACH50 as possible. Not every house I build will get to this standard as I'm sometimes limited by the Architecture on the weather-stripping of exterior doors. I've found that sliding glass doors, custom doors, "store front", and other Architecturally cool doors can really kill my blower door tests.
If you've followed my blog, I've used a ton of different methods to air seal inside a house. Spray foam, Owens Corning Energy Complete, Caulking, etc. Using these methods I've been able to get most houses below 2.5ACH50. But, to reach that goal of 1ACH50 I've decided to take a page from the PassiveHouse playbook and tape my exterior sheathing seams. In reading Martin Holiday's "Tape Test" article from March 2013 Fine Homebuilding, I thought that Siga Wigluv was the clear winner as the best tape for OSB sheathing seams. Martin's article says that it's best to use a primer and I fully agree. I bought my Siga tape online from SmallPlanetWorkshop.com along with the Siga accessories. I also recommend using a J-Roller to roll out the tape and ensure good adhesion. View the slideshow for some photos of the install process.
I made two videos of the Siga Tape. This first video is my impressions and a good destructive test.
Unfortunately, I've been waiting on the rear and front doors for this house so I've not been able to perform the blower door test! I'm expecting this house to get very close to my goal of 1ACH50! I'll post and update to this blog post once I get the results. Overall, I'm really happy with this Siga Tape and I think this method is superior from an Best Practice standpoint on that list of Control Layers.
Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.