Exterior Insulation & Finish System (EIFS) was originally developed in the late 1950s by a German called Edwin Hobish and was well suited to war torn areas following World War II. It came to the North America in the late 1960’s under the trade name Dryvit®. However, another German company coined the system as EIFS in 1979 which is the common name used within the construction industry today. The system is typically suited to warmer climates but is sometimes used in cooler climates also.
EIFS in its basic form consist of five components; the insulation board, the fastening system for the insulation board (adhesive or mechanical fasteners), the base coat, the reinforcing mesh, and a finish coat. The base coat, reinforcing mesh and finish coat is commonly referred to as a synthetic stucco. The synthetic stucco on the outer face is intended to be a water tight barrier to prevent water entering the building while the insulation layer keeps the building cool during hot periods and warm during cold periods. EIFS is often installed over concrete masonry unit (CMU), light gauge steel studs or wood stud walls.
EIFS is commonly used in new construction and many retrofits due to its advantages, detailed as follows. Adding thermal insulation to the exterior wall is good in any climate, helping to meet energy efficiency and climate change standards. It helps to eliminate thermal bridging at the exterior walls which are common when insulation is provided on the inner face or cavity of an exterior wall. EIFS is relatively inexpensive and easy to apply to the exterior wall. Architects also like the system due to its aesthetic options, as it can be installed with a variety of colors, textures and can be shaped to meet architectural desires.
Watch Out for Water Intrusion
Originally, Exterior Insulation & Finish Systems (EIFS) was a face sealed assembly which essentially relied on the exterior synthetic stucco face and joint sealants acting as a waterproof barrier to prevent water ingress. The main concern with face sealed EIFS stems from water intrusion. Sources of water intrusion can occur via failed joint sealants, improper detailing of flashings or cracks and holes in the face of the EIFS system. When water enters EIFS it becomes trapped between the insulation and inner leaf. As the outer face is intentionally designed to be a water barrier as to not let water in, this can create a barrier which prevents the saturated insulation ever drying out. Figure 1 below details the build up of a face sealed EIFS assembly.
Increased moisture levels within the EIFS has a negative impact on the thermal performance of the insulation but can also cause other issues. If moisture levels are above 20% then this may lead to wood fugus rot if the building is a wood structure, or if wood studs are used on the exterior walls. The fungus can go undetected for years and is not visually apparent on the surface. High moisture levels also create an environment suited to mold growth and various pests. These all have a negative impact on the performance of the EIFS system which eventually leads to its disintegration and complete failure of the system; and potentially damage to the building structure beneath the EIFS.
Improper design, specification and installation can severely affect the performance of EIFS. On the finished surface, any crack, penetration, detail, joint or opening is potentially a cause for concern for water entry. Conscientious EIFS design, detailing, installation and proper maintenance can help to mitigate the potential for water intrusion but this is often over looked. To counteract trapped moisture some EIFS assemblies have been designed to include a drainage plane to allow any water that penetrates the synthetic stucco to drain out of the system. Figure 2 below details a drained EIFS assembly.
Inspection and Maintenance Considerations
Exterior Insulation & Finish Systems (EIFS) should be routinely checked for deficiencies to ensure that the system does not fail, and water intrusion is prevented. This is even more important for a face sealed EIFS assembly than a drained EIFS assembly but it’s good practice to regularly check both. The following system components should be checked;
Many exterior insulation and finish systems (EIFS) systems have elastomeric type joint sealants at panel joints and around fenestration openings. These sealants have two functions: to accommodate movement, expansion and contraction of building materials; and provide a water tight barrier at the joints. As the sealants age, then solar ultraviolet (UV) degradation can dry the sealant material out whereby they become brittle, lose their flexibility and cease to function as intended. If the sealant is found to be brittle or have signs of either cohesive (failure within the sealant joint) or adhesive failure (failure at the joint between the sealant joint, and the adjacent surfaces), then they should be replaced immediately. Most elastomeric type sealants have an estimated useful life of 10 to 15 years. Care should be taken when removing sealants as to not damage the synthetic stucco.
The synthetic stucco is typically the first line of defense an EIFS system to prevent moisture entering the system. The stucco should be inspected for cracks or holes and any damaged areas need to be repaired immediately to prevent water intrusion. The paint finish should be inspected for “thinning” and if there are signs of reinforcing mesh being exposed then it is time to repaint and perhaps reapply the finish coat to select areas. A paint approved by the EIFS manufacturer should be applied every 5 to 10 years depending on location and quality of the paint used. The EIFS can be washed every two to three years to maintain the appearance of the building providing it is water tight.
The Exterior Insulation and Finish (EIFS) system should be checked for any wet spots of insulation, particularly following a heavy rainstorm or prolonged period of rain. Initially, an evaluation can be visual in nature but if areas are cold on the back of the hand or make a different sound when gently tapped with a hard object then this could be an indication that the insulation beneath is wet. An infra-red survey of the exterior walls will confirm the extent and locations of wet insulation within the EIFS systems. If anomalies are identified then the source of water intrusion should be removed, and wet areas of insulation should be removed and replaced immediately. We suggest the wet spots are confirmed with moisture meter readings prior to replacement.
Flashings and Penetrations
The adequacy of flashings, connections and penetrations or fixings to checked to ensure the barrier face of the exterior insulation and finish system (EIFS) is protected from water intrusion. Exterior wall mounted lights, signs, or service penetrations are common weak spots for water to enter the EIFS. Contractors that are not familiar with the importance of maintaining the water integrity of an EIFS system often damage the system unintentionally, or do not provide adequate detailing when fixing or fastening something to the exterior wall.
General detailing of the exterior walls should be inspected. Horizontal architectural bands, balconies, window lintels and sills, and even grade level surfaces should positively drain away from the EIFS wall system. If any ponding is present in these areas, then there is cause for concern. As a rule of thumb an EFIS system should be elevated at least 8” above grade level or the surface of a balcony or low-level roof.