The idea behind exterior insulation and finish systems (EIFS) is attractive: a continuous insulated skin that’s lightweight, versatile, and energy-efficient. Those advantages made EIFS popular in the 1980s and 1990s, but then disaster struck in the form of widespread moisture problems. EIFS jobs were plagued by poorly done flashing of penetrations and sealing of joints. And the system’s foam insulation and acrylic skin trapped moisture—so walls that leaked couldn’t dry out.
Lawsuits destroyed the market for EIFS in home building. But manufacturers have bounced back with new “drainable EIFS” that have backup drainage to let water out if it leaks past the outer skin. (The new methods also rule out using poly vapor barriers under the drywall, so the interior wall faces won’t trap moisture if the outer face does leak.) Building science guru Joseph Lstiburek, who as an expert witness helped seal the doom of barrier EIFS, is a fan of the new drainable version. And attorneys say the lawsuits have largely dried up and blown away.
Different brands of drainable EIFS use different details, and the industry says it’s a bad idea to mix and match. But here’s a look at the elements that the new EIFS methods have in common.