DESIGNING AN INTEGRATED WALL SYSTEM

Building scientists have learned a lot about the integration of materials into a wall system. The moisture inside buildings is as important as the moisture outside of the building. Some interior finish materials and wall coverings, if not well ventilated will prevent moisture from evaporating. This can create condensation in a wall cavity and lead to mold. Building scientist Joseph Lstiburek of Building Science Consulting has taught numerous architects about the value of moisture dynamics as learned through forensic studies. He recommends that architects pay attention to the difference in climate in the North versus the South. The wall system that breathes may mix and "match sheathings, building papers and cavity insulations" and "should be based on climate location."¹³

Top: Conventional EIFS system. Bottom: EIFS with Drainage Images provided by EIMA

Professionals should research each material in a wall system with regards to climate. The average temperatures, hot, cold and humid climates will determine where the vapor barrier, insulation and sheathing should be installed, to prevent condensation and mold growth. The type of insulation and sheathing materials will also react to climate, and most professionals will require field mock-ups of the entire wall system to test designed performance values. Manufacturers of insulation and building materials can provide expertise on system design through their building science divisions.

It is not just the material used as a cladding, but the method and controls involved in the application. EIMA's Steve Klamke reported on a study by Oak Ridge National Laboratory which reviewed the moisture and thermal performance of an EIFS wall system with a drainage system to other exterior claddings. The researchers considered the entire building envelope, not just isolated materials or component systems.

Oak Ridge laboratory found that this EIFS panel excelled in thermal and moisture performance. Graphic courtesy of Oak Ridge Laboratory

This research determined that an EIFS wall system consisting of four inches of expanded polystyrene insulation board and a drainage assembly, without any interior stud insulation provided excellent moisture protection while maintaining superior thermal performance. According to researcher Achilles Karagiozis, "The Department of Energy (DOE) initiated a research project within Emerging Technologies group to investigate the performance of exterior insulation systems. This was part of the DOE effort to provide Zero Energy houses with a new line of highly efficient thermal wall systems. The Oak Ridge National Laboratory teamed up with EIMA to compare the real life performances of a number of walls with and without exterior foam simulation (EIFS, Stucco, Brick, Cementitious siding). Only water managed EIFS walls were monitored during a three-year period, and the results clearly indicate excellent thermal and moisture performance for the newly developed moisture engineered EIFS systems. These innovative EIFS walls include an exterior weather resistive barrier that is applied as a liquid, an exterior drainage system with vertical ribbons of adhesives that provides a drainage path and an unvented air space that increases the drying capacity of the walls. This system imparts high thermal performance and a very high moisture performance when the proper vapor retarder is used on the interior side of the wall."¹⁴