SYSTEMS/GLASS AND METAL CURTAIN WALLS
Corners
When two sections of curtain wall meet at a
ACCEPTABLE
corner, an air barrier must be fabricated to
connect the two sections. Such a
gid air barrier and
connection is shown in Figure 4.1.10. The
air barrier and its attachment must be
structurally adequate to carry the wind
pressure loads. The air barrier can be
fabricated of sheet metal, with consideration
given to the corrosive potential of dissimilar
metals. In a heating climate, the air barrier
must be insulated on the outside with the
insulation in intimate contact with the air
barrier and in line with the mullion thermal
breaks. The decorative cap outside of the
insulation serves as a rainscreen and must
not be sealed airtight to the mullions.
Figure 4.1.10 Curtain Wall Connection at Corner
(Quirouette)
Grade Connection
Figure 4.1.11 shows two curtain wall connections to grade, one with poor thermal performance and
an improved alternative. The connection between a curtain wall and grade is particularly sensitive
to rain penetration and air infiltration. The first detail violates the requirements for both air barrier
and insulation system continuity. The insulation under the mullion is out of line with the mullion
thermal break, and the air seal under the mullion is out of line with the mullion air seals. In addition,
cold air infiltration past the flashing and into the insulation creates the potential for condensation on
the interior of the mullion. Rainwater accumulation in the cavity between the wall section and the
floor will deteriorate the floor-to-mullion air seal. The alternate detail maintains the continuity of
both the insulation and air barrier systems. The insulation is located to control condensation on the
interior of the air barrier. A sealant is used at the base of the air barrier to create a sloped edge or
water dam to control rain penetration. Flashing is installed under the mullion cap to ensure that
water draining from above is directed to the outside of the cavity.
ACCEPTABLE
UNACCEPTABLE
Figure 4.1.11
Curtain Wall-Grade Connection (Quirouette)
PAGE 4.1-8
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