DESIGN/RAIN PENETRATION
Figure 3.4.7 shows a simple one-stage joint in a precast panel wall system from Rousseau. In the
so-called face seal approach, a single line of defense is employed against both rain penetration and
air leakage. Although this approach has low first costs, the sealant is fully exposed to the
degrading effects of sunlight, ultraviolet radiation, water and temperature cycling. Over time the
performance of these sealants will decrease, increasing maintenance costs.
Figure 3.4.7 Precast Concrete Panel - One-Stage Joints (Rousseau)
A two-stage joint in a precast panel is shown in Figure 3.4.8. The outer rain seal serves to control
water leakage due to kinetic energy. Any rainwater that does penetrate the rain barrier drains to the
outside, before it is able to reach the air seal. The inner air seal is in a less severe environment,
being protected from water and ultraviolet radiation, easing the material requirements on the
sealant.
Figure 3.4.8 Precast Concrete Panel - Two-Stage Joints (Rousseau)
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