Replies

1. 
   Steve Knapp CZ 3A Georgia|Oct 06, 2017 09:42am|#1

   Norman,

   I think it would depend on whether you did any air sealing while installing the sheathing. Did you apply caulk or construction adhesive to the framing before attaching the sheathing? Did you tape the seams on the exterior side of the sheathing?

2. GBA Editor
   Martin Holladay|Oct 06, 2017 09:42am|#2

   Norman,
   As far as I know, EcoSeal works. That doesn't necessarily mean that it's the most cost-effective approach to air sealing, of course. But it works.

   Here are links to two GBA articles on EcoSeal:

   Air Sealing With Sprayable Caulk

   EcoSeal: A New System for Air Sealing Homes

3. 
   Norman Bunn|Oct 06, 2017 03:12pm|#3

   Steve: We will be air sealing the sheathing. I won't need to adhere the sheathing to the studs, I guess, if I use the Ecoseal. The demos of Ecoseal show sealing the sheathing joints, too.

   Martin: Thanks for the links. Very helpful.

4. Expert Member
   Dana Dorsett|Oct 06, 2017 03:55pm|#4

   Air sealing each individual stud bay guarantees that random leak points anywhere in the sheathing layer stay localized, allowing very little air movement from stud bay to stud bay, up, down, or sideways. To skip that step and only air seal the sheathing means you're counting on the air sealing details on the sheathing to be

   A: done perfectly on day-1...

   ...and...

   B: ...to REMAIN perfect forever(?).

   In theory perfect air barriers are great.

   In reality there is only good, better, and best, but no such thing as "perfect". Redundant air barriers and sealing measures is just good practice. "Good practice" doesn't make "perfect" either, but it does make "better".

   With a powered caulking gun ad a few cases of polyurethane caulk or acoustical sealant it doesn't take much time to caulk the framing to the sheathing (and between the bottom plate & subfloor, and seams between doubled-up top plates, jack studs, etc). Even if it adds up to a few hundred USD in material it's cheap insurance for fiber-insulated studwalls. If it's going to be insulated with open cell foam it's not necessary, but it's still worth caulking the seams in doubled up framing, etc.

   For similar reasons it's worth can-foaming or caulking all electrical penetrations in the framing at every stud too.

   Note: In seismic zones using polyurethane caulk or construction adhesive in every stud bay makes the wall assemblies more rigid than local codes allow, which makes the walls more prone to walking off the foundation during the big 'un. In those areas acoustic sealants would still be allowed, due to a much weaker bond. If your local codes have lots of seismic hardening details, check with the inspectors first.

5. 
   Jamie B|Oct 10, 2017 10:58am|#5

   Hey all,

   I am about to start "picture framing" my stud bays.

   Is there any preference of caulk vs foam regarding air tightness?

   I am leaning towards using canned foam since it'll be faster for my to apply it. I'm planning on using this flex foamhttp://www.tremcosealants.com/products/exoair-flex-foam.aspx

   thoughts?