Page 13 - CodeWatcher Summer 2017

Energy Code Minute

Metal Building

Meets an Air Barrier

We focus so much on the Residential Energy Code that we forget there
actually is a Commercial Energy Code, and that they are different when it
comes to some assemblies like walls.

BY STEPHEN CARR strength and direction
of the wind on a par-
OES YOUR AIR BARRIER MOVE? Funny ticular day. Yet, we still
question, right? Well, for those who meet the code by having
own metal buildings using laminated the air barrier installed
insulation as their fi nished product, this on the interior side of
question may not be far-fetched. Now, Credit: Service Partners the building envelope.
put that building at a high elevation or What about the metal
Dalong the coast where wind is almost sheeting on the build-
always at or above 10 mph, and the question makes even The red arrow on the metal sheeting ing? The sheeting itself
more sense. indicates where there is a gap that is an air barrier, yet in
We actually had this very situation. The metal building needs to be sealed with a panel this and many other
was in a high wind area, and the laminated insulation was closure strip. cases it does not get
installed very well, sealed like a roof because the interior laminated insulation
all seams sealed, and is the air barrier. So, no additional steps need to be taken,
penetrations sealed right? Well, it depends. Does your building owner want to
creating that contin- have their air barrier move?
uous coverage. What For those wanting a fairly air-tight metal building, you will
happened in this case need to seal your exterior metal sheeting with panel closure
is that the “air barrier” strips for the ends of each panel and sealant (caulking or
moved, “ballooned,” other) to air seal the seams of each sheet. Treat your walls as
made noise which was you do the roof assembly. You would not want water entering
not what the building your roof, why let air enter your wall cavity?
owner was looking for. I am biased on this topic and encourage builders to always
So, why did this hap- seal the wall assembly at the exterior sheathing. The reason
pen? Credit: Service Partners is simple: It works 100% of the time with signifi cantly less
As we know, code obstructions than sealing from the interior.
gets us started in a di- Just because the code says you can choose inside or outside
rection, yet in some Here, laminated fiberglass insulation does not mean both options are the same or are right for the
cases does not help us is shown as the finished product. building. It just means that your building offi cial is looking
to identify issues prior to them showing up in real life. for it at either location. CW
Section C402.5.1 of the 2015 IECC Commercial Code states:
“A continuous air barrier shall be provided throughout Stephen Carr is Regional Building Science
the building thermal envelope. The air barriers shall be Manager for TopBuild Home Services.
permitted to be located on the inside or outside of the Have questions? Email him at
building envelope, or any combination thereof. The air stephen.carr@topbuild.com
barrier shall comply with Section C402.5.1.1 and C402.5.1.2.”
In this case, the code does not tell us that not sealing the
outer metal sheeting, the wall assembly can be pressurized
and make the laminated insulation move depending on

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