EIFS with Drainage

The month of May treated us with not one but two virtual meetings of the Willamette Valley Chapter of the Construction Specifications Institute. In addition to the earlier presentation about Jeffrey Commons, the tiny home village developed by Sponsors, we enjoyed a second meeting on the subject of Exterior Insulation Finish Systems (EIFS) with integral drainage technology. 

Bret Bastain, CSI, CDT, National Accounts Manager for Parex USA. Parex is an industry leader in continuous insulation, stucco, and architectural coatings and finish systems. Bret provided a comprehensive overview of state-of-the-art EIFS technology, including a listing of the key benefits and important considerations of EIFS systems, the various codes that impact their use, and why incorporation of a means to drain infiltrating moisture is essential.  

EIFS has been around since the years immediately following the end of World War II. Manufacturers in Europe developed the technology, spurred by the need to quickly rebuild war-ravaged cities there. EIFS has been available in the US market for the past forty years. It quickly gained favor in new commercial construction. Its prevalent usage today remains the non-residential marketplace, which accounts for 90% of its applications. Today, the area of installed EIFS in this country amounts to billions of square feet, or approximately 30 percent of all cladding on new commercial structures.  

For those who may not be entirely familiar with what an EIFS is, simply stated it is an integrated insulating, decorative and protective exterior cladding system for buildings. Chapter 2 of the Oregon Structural Specialty Code defines EIFS as “nonstructural, non-load bearing, exterior wall cladding systems that consist of an insulation board attached either adhesively or mechanically, or both, to the substrate; an integrally reinforced base coat and a textured protective finish coat.” The finish is often rendered to resemble traditional stucco, so people often refer to EIFS “synthetic stucco;” however, this is somewhat of a misnomer because technically “synthetic stucco” refers to the acrylic finish coating only.  

I first became acquainted with EIFS when I started my professional career in Canada during the early 1980s. The widespread use of the system in Canada predates its broad acceptance in the US by a few years. Unfortunately, the original, face-sealed (“barrier”) EIFS products would reveal elemental flaws in their application. The resultant failures and lawsuits—almost all attributable to moisture infiltration and the resultant mold infestations and structural damage—would threaten the very existence of EIFS manufacturers. This crisis spurred the industry to respond, which it did by developing drainable EIFS. 

Notwithstanding its troubled history, EIFS presents an attractive cladding option for designers and builders. Bret enumerated just a few of the key benefits of EIFS:

• Exceptional energy efficiency
• Reduced thermal breaks through the building envelope
• Resistance to structural movement without surface cracking
• Aesthetic design flexibility
• Low maintenance
• Light weight
• Durability
• Low cost
• Green building and LEED benefit

  
  

  
  

The problem with standard barrier assemblies is their water-barrier functionality begins at the surface. They do not provide means for draining incidental moisture infiltration and are dependent upon flawless installation of the entire system. Carefully detailed and correctly installed sealant and flashing are critical to surface/barrier EIFS. 

Incidental moisture occurs within wall cavities due to temperature and pressure differentials, and the reality of improper sealant and flashing applications or the lack thereof. It just takes a combination of three factors—moisture + an opening + a force (e.g. wind)—to result in potentially harmful moisture intrusion. EIFS with drainage acknowledges the inevitability of water intrusion by incorporating paths for moisture to escape from within the exterior wall assembly before it has an opportunity to cause problems. 

The critical components of drainable EIFS that distinguish it from conventional EIFS include a water-resistive barrier (WRB), air barrier, and drainage plane. 

Water-resistive barriers occur behind the exterior wall covering. They’re intended to resist liquid water that has penetrated behind the exterior covering from further intruding into the exterior wall assembly.  

Air barriers prevent air leakage and infiltration and isolate the interior and exterior environments. Notably, energy codes do not require air barriers in buildings located in Climate Zones 1, 2, and 3. Eugene is in Climate Zone 4, so air barriers are necessary here.  

WRB options include: 

• Self-adhering membrane sheet materials. Some self-adhering membranes are permeable whereas most are impermeable. They’re not always “user friendly” because their installation demands a high skill level. 
• Traditional sheet wraps. The integrity and sealing of their overlapping seams impact the overall effectiveness and performance of sheet wraps. They also require fasteners that puncture the membrane.
• Liquid-applied membranes are seamless and monolithic, eliminating concerns with overlaps and unsealed seams. There are no fastener penetrations associated with liquid-applied membranes as they are directly bonded to underlying sheathing or masonry.

 Some WRBs function as barrier to both liquid moisture and air leakage and infiltration. 

The drainage plane is critical because it provides a physical path for moisture to escape, principally relying upon gravity to initiate vertical movement and evacuation. To be effective, the drainage plan requires a minimum 1/8 inch gap between the WRB and the backside of the continuous insulation board of the EIFS. Most commonly, vertical adhesive ribbons provide the necessary gap. They offer the best multifunction performance (being the adhesive, base coat, and drainage plane), best wind-load resistance (by transferring the wind load to the entire substrate), no fastener penetrations, and the simplest, fastest installation. 

The International Energy Conservation Code (IECC) and the 2019 Oregon Zero Energy Ready Commercial Code (ASHRAE 90.1-2016) require continuous insulation, which EIFS readily provides. 2 to 4 inches of EPS typically satisfy the requirements of most climate zones. 

The finish component of EIFS assemblies have also evolved in response to the marketplace. Impact-resistant coatings are increasingly prevalent. High usage and wear areas require special consideration. Impact resistance can be achieved through the use of heavier reinforcing mesh, incorporation of an additional layer of conventional mesh, and/or the use of a high-impact basecoat. Bret did suggest architects consider incorporating thin brick or stone veneer in the façade assembly for even greater impact resistance where warranted for aesthetic reasons. 

And speaking of EIFS finish options, Bret cited the wide variety of coatings and finishes possible (including thin masonry veneer systems). The available range of colors and textures is only limited by your imagination. 

EIFS manufacturers (represented by the EIFS Industry Members Association) responded decisively to address the shortcomings of their original surface barrier systems by creating cost-effective, versatile, drainable alternatives. Thanks to Bret for providing those of us who participated in the virtual WVC-CSI chapter meeting with an excellent primer on EIFS with drainage. I hope to “see” more of the readers of my blog at our next opportunity to meet.