EIFS and its components Exterior Beyond EIFS’ continuous insulation on the outside of exterior walls, the System aspect of EIFS places other key components on the exterior side of the wall. The System’s required Water Resistive Barrier (WRB) has the primary function of protecting the underlying structure. However, it can also act as the control layer capable of managing wall system behaviors such as air leakage and vapour dif- fusion. Today, all EIFS designed in compliance with the newly codified i S716 series of ULC Standards must include the WRB (water resistive barrier). The required performance characteristics of the WRB are very stringent and in com- parison to traditional building papers, having a water ab- sorption coefficient that is established over three days ii as opposed to paper’s old 30 to 60 minute rating system. The WRB is able to provide effective air leakage control as a key component of the wall’s air barrier system. All EIFS manufacturer’s Liquid Applied WRBs reviewed have a tested air leakage rate of less than the code’s required 0.02L/(sq. m.) @75Pa pressure difference iii . They’re also available in a range of vapour permeance ratings, affording the designer the ability to balance WRB permeability and wall system characteristics, with the building’s interior moisture load and the external environment. Having these two key control layers on the same plane within the wall is desirable for a variety of reasons, simpli- fication of construction being just one. The location being both external and protected, renders the approach ideal. Conceptually, and of course figuratively speaking, Dr. Joseph W. Lstiburek describes this arrangement, along with a protective cladding and exterior insulation as com- prising the “Perfect Wall.” iv Figure 1. Exterior Layers Insulation The exterior insulation of EIFS has been part of the sys- tem’s make-up since its inception. Always touted by its proponents as having greater effective R-value than many alternative approaches, the degree of difference and vali- dation of that difference has only recently found its way into accessible documentation such as ASHRAE’s 90.1 En- ergy Standard for Buildings Except Low-Rise Residential Buildings. Further to what can be drawn from 90.1’s con- tinuous insulation and the effective R-value of a between the stud approach are the effects of “thermal bridges” lo- cated elsewhere in the exterior wall. While suspected for years by the building science com- munity and academia as necessarily impacting effective R- value v , the actual impact hadn’t found its way into the public domain. That changed with the publication of B.C. Hydro’s “Building Envelope Thermal Bridging Guide.” Pre- pared by Morrison Hershfield, the exceptional and exten- sive research shows that some exterior insulation strategies can experience as much as a 50 per cent reduc- tion in their reported clear wall R-value vi . While not immune to thermal bridging (at locations such as windows), EIFS requires minimal accommodation to significantly reduce their impact and preserve the systems’ continuous insulation value. EIFS’ cost effectiveness and the degree to which it effectively preserves energy, can free up monies to enhance and improve other envelope features such as thermally broken parapets and bal- conies vii . Cost savings can also be applied to investments in higher efficiency heating and cooling systems. Finish The array of finish options has grown considerably in recent years, to the point where EIFS can mimic any num- ber of alternative cladding looks. However, some techno- logical improvements may not be as readily apparent, at least not until the building has been in service for a number of years. EIFS manufacturers have made im- provements in finish performance relating to colour-fastness and dirt pick-up resistance. While not exclusive to the EIFS industry, the use of non-organic colour-fast pigments as found in automotive paints and other high per- formance coatings have been adopted into a number of available finish options. Described by one proponent as Plus Finishes, Nano- chemistry and other technologies have been harnessed by a number of EIFS finish produc- ers to provide extended colour fastness and a cleaner exterior. Beyond the cosmetic, some finishes possess IR (insulation resistance) re- flective technology with the ability of cooling exterior wall temperatures and reducing cool- ing costs. The Canadian Design and Construction Report — Winter 2015 – 53