DESIGN/AIR BARRIERS
ACCEPTABLE
Curtain Walls: In curtain walls the air
barrier consists of the glass, metal pan and
extrusions, insulation and sealants. Figure
3.1.6 shows the basic approach to providing
Metal spandrel
an air barrier in the system. The metal pan
behind the spandrel insulation and the
vision glass are the major elements of the
air barrier; they must both be joined to the
mullion using appropriate sealants to
maintain the air barrier continuity.
Figure 3.1.6 Curtain Wall Air Barrier
(Perreault 1989)
Metal Buildings: In metal building systems, the interior sheet steel liner serves as both an interior
finish and a combined air/vapor barrier. Since the metal liner is airtight, the panel joints are the
critical elements in the air barrier system. Care is also required in the design of wall/roof
intersections and at the bottom of the walls in these systems.
Masonry Walls: Various approaches have been
ACCEPTABLE
used for air sealing masonry walls. Factory-made
elastomeric membranes provide a reliable air
barrier, with the membrane being applied to the
entire surface of the masonry backup wall as
shown in Figure 3.1.7. These membranes may be
thermofusible or peel-and-stick. Thermofusible
membranes are adhered to the backup wall by
heating the membrane backing with a propane
torch. Insulation can be held in place with metal
clips heat welded to the membrane. A sketch of
Membrane
an elastomeric membrane air barrier applied to a
air/vapor barrier
masonry wall is shown in the figure. The
membrane runs continuously past the floor slab
providing good continuity. Note the gap between
the top of the backup wall and the bottom of the
floor slab to accommodate deflection of the floor
slab or other differential movement between the
backup wall and the building structure.
Figure 3.1.7 Masonry Wall
Air Barrier
(Perreault 1989)
PAGE 3.1-7
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