Properties of Exterior Insulation and Finish Systems
Exterior Insulation and Finish System (EIFS) (pronounced ‘eefs’) – non load-bearing wall cladding system comprised of liquid-applied, water resistive barrier (LA-WRB), an adhesive for attachment of the thermal insulation board to the LA-WRB, rigid thermal insulation board, a glass fibre reinforcing mesh embedded in a base coat on the face of the thermal insulation board, and a finish coat.
The emphasis is on system. EIF systems are the original continuous insulation (CI) claddings that wrap a building with a thermal blanket. It’s like pulling on a warm sweater in winter.
EIFS is an engineered, six component system that is developed, tested and evaluated to rigorous performance standards. No other cladding is tested and evaluated as thoroughly as EIFS.
EIFS are proprietary. Manufacturers invest heavily in research and product development. Performance is continually enhanced but what is probably most notable are the fabulous finishes available. Components may not be interchanged with other manufacturers.
EIFS Is Resilient
EIFS require a structural substrate for support. Typically wood frame for single-family residential construction or steel framing with water resistive gypsum based sheathing. Masonry, such as hollow concrete block has been insulated with EIFS.
Liquid-Applied Water Resistive Barrier (LA-WRB)
The LA-WRB is the final line of defense against water penetration into the building envelope. In Canada two coats or applications are required. No other WRB in the construction industry is tested and evaluated to the degree that the EIFS LA-WRB must meet. If the wall assembly is properly designed to as per code, the LA-WRB will never get wet; the true meaning of redundancy.
Water Resistive Barrier (WRB)
The substrate is protected by a waterproof air barrier system. The ‘system’ consists of durable joint treatment and other connective elements that tie the WRB to other components on the building envelope.
Where the EIFS terminates, consideration must be given to air barrier connections and deflecting water away from the wall assembly. This requires coordination and sequencing with different trades on the building. The beauty of a LA-WRB is that flashings may easily be integrated into the drainage system without concern about ship-lapping membranes. All the applications bond into one monolithic layer.
Flashings shall be designed to terminate outbound of the wall cladding (code requirement) and shall be durable. Consideration should be given to thermal bridging and materials that have improved thermal performance. [Read More]
Adhesive and EIFS Termination
There are two methods for installing the insulation to the LA-WRB. One method is to bond the insulation into the second layer of the LA-WRB designed to be both adhesive and water resistive barrier. Only insulation a geometrically defined drainage cavity (GDDC) must be used in this application. More common is the use of adhesive ribbons installed with a notched trowel to the back of the insulation. The insulation is securely pressed into place. The space between the ribbons allows any penetrating water to drain to the flashing below and out of the wall. The drainage cavity does not need to be large. A 2 mm drainage cavity drains 99.8% of the water that is introduced during testing. No other cladding has been shown meet that efficiency.
In Canada, Part 9 National Building Code requires GDDC insulation to accommodate for substrate irregularities that may cut off the space between vertical ribbons. In Ontario, the insurer for most architects, requires GDDC insulation for all projects.
The insulation at EIFS terminations require the base coat and reinforcing mesh to be ‘wrapped’. This protects combustible insulation in the event of fire and provides a surface for sealant joints. [click to sealant joint blog] Terminations designed to drain water must be pre-wrapped prior to installation. The insulation used for the prewrap should be shaped to accommodate flashing and other elements at the back so drainage is not blocked. Pre-wrapped starter pieces are also available commercially but beware – they must use the manufacturer’s base coat and mesh and must comply with the system’s fire evaluation report. Not all are equal so only use pieces recommended by the EIFS manufacturer. The advantage of commercially manufactured pieces is the quality control available in the process and the time saving in the installation.
Insulation is the heart of the system. EIFS are extraordinary in appearance but the high ‘R’ value is where the real inner beauty resides.
Almost all EIFS use expanded polystyrene insulation (EPS) with an RSI value of 0.68 per 25mm (‘R’-Value 3.85/inch). Most systems are evaluated with 100 mm (4”) or more insulation. Mass walls such as concrete or masonry can be maintained at almost constant temperatures. Stud walls can have cavity insulation plus massive exterior thermal insulation.
There is huge design flexibility with the ability to shape insulation. Cornice, quoin and carving can be done with the insulation to create style or signage.
Durability and resiliency can be built into the system with layers of base coat and reinforcing mesh. Heavy duty reinforcing mesh, embedded into base coat, is recommended at grade and any location where impact is expected. How tough is it?
Heavy reinforcing meshes are too stiff to overlap so edges must be butted together. A second layer of base coat and mesh is always installed over the tough mesh to increase impact resistance and prevent cracking at the mesh butt joints.
Base coat, Embedded mesh and Finish (Lamina)
The EIFS base coat is installed over the insulation or heavy duty reinforced base (as illustrated) and, the reinforcing mesh is embedded into the wet base coat. Manufacturers have different colours and logos to identify their mesh. Beware of mesh that is not supplied by the manufacturer. Legitimate mesh is tested under a very severe protocol that few products can meet. It is a critical component for the long-term durability and performance of the system.
Regular mesh is over lapped a minimum of 65 mm. In this illustration the mesh overlaps the prewrapped starter by at least that amount. Additional strips of mash may be used to connect the prewrapped starter pieces where they are butted together. In all cases with EIFS installation, the reinforcing mesh must be overlapped to insure continuity.
Although optional, EIFS industry experts strongly recommend the use of a coloured primer over the base coat before the finish is applied. It will provide a better depth of colour and finished appearance. Some special finishes use a clear acrylic binder. In those cases the primer is mandatory. Other finishes, such as faux brick, the primer is exposed and requires a UV resistance.
Where to begin …? EIFS standard finish is available in millions of shades and hues. Why boring beige is the predominant colour remains a mystery to the industry. There are limitations on very dark colours because they will get too hot for the insulation, therefore, avoid black. Aside from that colours and combinations of colours can create dynamic appearances far beyond what is available in any other cladding.
And that’s just the beginning! Manufacturers have developed finishes that look like everything from metal to granite to brick. There are finishes that repel dirt and water and finishes that have IR reflecting pigments to keep dark colours cooler. The choice and potential for design is breathtaking.
To Explore How I Can Help You With EIFS