Learn About Exterior Insulation and Finish Systems
Click the labels to explore the layers.
Substrate and Wall Structure
EIFS require a structural substrate for support. Typically wood frame for single-family residential construction or steel framing with water resistive gypsum based sheathing for commercial. Masonry, such as hollow concrete block (CMU) or brick, is the traditional substrate for EIFS. Many leaky, uninsulated masonry buildings have been retrofit and saved by over-cladding with EIFS.
Joint Treatment
The substrate is protected by a waterproof air barrier system. The ‘system’ consists of durable joint treatment with a liquid-applied water resistive barrier over. Building movement is focused at sheathing joints so the joint treatment durability receives separate testing and evaluation.
Waterproof Air Barrier System
The liquid-applied water resistive barrier (LA-WRB) is the final line of defense against water penetration into the building envelope. In Canada, two coats or applications are required.
Traditional sheathing membranes such as building paper and house wraps are NOT acceptable for use with EIFS.
http://eifscouncil.org/wp-content/uploads/2015/10/ECC-Bulletin-8-Mechanical-Attach-over-wraps.pdf
If the wall assembly is properly designed, as per code, water will be deflected away from openings and the LA-WRB will never get wet; the true meaning of redundancy. EIFS is dry by design.
Adhesive
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 with a geometrically defined drainage cavity (GDDC) may 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 then 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 to provide equivalent efficiency.
Insulation with GDDC
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.
EIFS provides unique design flexibility given the ability to easily shape insulation. Cornice, quoins and carving can be done with the insulation to create style or signage.
GDDC – Geometrically Defined Drainage Cavity – In Canada, Part 9 National Building Code requires GDDC insulation to accommodate for substrate irregularities that may cut off the space between vertical adhesives ribbons. In Ontario, the insurer for most architects requires GDDC insulation for all EIFS projects. The user should be aware that GDDC is more complicated to install and following manufacturers instructions is important.
The EIFS drainage cavity, either with vertical ribbons of adhesive or with properly compartmented GDDC, has been demonstrated not to compromise the effective insulation value of EIFS cladding.
Heavy Duty Reinforcing Layer
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 with Embedded Mesh
The EIFS base coat is installed over the insulation or heavy duty reinforced base (as illustrated). 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.
Coloured Primer
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.
Finish
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.
Wrapped Termination
The insulation at EIFS terminations requires the base coat and reinforcing mesh to be ‘wrapped’ around the insulation. This protects combustible insulation in the event of fire and provides a surface for sealant joints. [click to sealant joint blog] Before wrapping, the foam must be shaped to accommodate flashings and membranes to ensure a clear path for drainage. A gap of 1 or 2 mm is adequate for water to flow. 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.
The pre-wrapped mesh must be overlapped with the regular mesh by at least 65 mm. 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
Flashing
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.[http://www.buildingsciencelabs.com/consulting/drip-edges-devil-details/ ]
Waterproof Air Barrier System Integration with Other Systems
The building’s air barrier system must be continuous around the whole building envelope and must be durable. That means that where the EIFS waterproof air barrier terminates, it must be connected to the adjacent material in a durable manner. Coordination with other trades, careful installation sequence planning and assurance of material compatibility is required. This should never be left undetermined in the construction process. The time and effort required to get it right is nothing compared to the cost of getting it wrong!
Illustrations by Oz, Shop Drawing Services.
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