Exterior Insulation & Finish Systems

Exterior Insulation & Finish Systems Problems

The problem we face now is, sometimes an individual contractor may fail to fully follow the manufacturer's installation guidelines.  Often times only a portion of the guidelines are followed, materials from different manufacturers are inter-mixed, etc.  This can allow moisture into the wall system.  Once the moisture is in it can't get out, which can lead to wood rot.  Some of the more common installation “short-cuts” are listed below:

• Foam insulation placed below grade. Prior to recent building code changes, the foam board insulation used in EIFS was placed on the wall below grade. It was discovered that foam in contact with the ground causes conditions conducive to pest infestations (termites, carpenter ants, etc.). With EIFS-clad homes, the visible evidence of infestation is blocked from view by the exterior siding. In fact, the exterior siding typically looks pristine and shows no signs of any problems. Behind the EIFS cladding, pests can live in a protected environment and then establish themselves inside the home. 

• Another problem with placing the foam below grade is the ability of water vapor to migrate upwards through the foam. When the temperature rises at the transition from masonry to wood, the water vapor condenses and causes water to settle on the sill plates and exterior band joist. If this water does not evaporate quickly, wood rot can set in and decay the structural members of the home.

• Improperly flashed & caulked windows.  Window leaks account for the majority of water damage in EIFS houses. The EIFS itself isn't usually leaking; instead, water is entering between the window and the EIFS, or the window itself is leaking water. The solution requires a window flashing that works, as well as a correctly detailed joint between the window and the EIFS wall. Wherever a window, a door, or an electrical or plumbing fixture interrupts the EIFS surface, a proper joint must be constructed, that integrates a reliable flashing into the secondary weather barrier.

• A very important component that is often missing in window detailing is the backer rod.  The backer rod serves two functions: First, it prevents the caulk bead from adhering to the back of the joint, allowing the caulk to flex in response to thermal expansion and contraction and other building movements. If the backer rod is omitted, the caulk will adhere to the back of the joint as well as the sides, limiting its ability to stretch and guaranteeing premature failure. Second, it controls the thickness of the finished application of caulk, which should ideally be about half as thick as it is wide. More often than not, though, the caulk and backer rod are never applied at all. It is important to keep in mind that no residential windows arewaterproof, they are designed and manufactured to a water-resistant standard. The very best windows allow some water into the wall cavity through their own joints, and “construction grade” windows may leak a great deal. The quality of windows installed with the EIFS is directly related to the amount of water that will infiltrate. For example, wood windows perform poorly, while welded seam vinyl windows perform substantially better than other window types. EIFS homes cannot be made totally "water proof", and windows will leak. Regardless of how well the backer rod/sealant method seals the joints between window and the edge of the EIFS wall, windows will leak at some point (even those caulk joints made under laboratory conditions by EIFS industry engineers will eventually fail).

• Flashings missing or improperly installed. are an important element in protecting your house from leakage, and should be utilized to properly direct water away from the structure.  Some of the more common locations where they are required are: deck ledger boards, kick-out flashing at roof / wall intersections, at window and door heads, headers and other horizontal surfaces, etc.  All too often, flashings are not installed, or installed improperly.

• Roof termination. EIFS should be held off of roof a minimum of two (2) inches and backwrapped.

• Expansion joints at dissimilar materials. Expansion-joints should be used where EIFS terminates, or meets a dissimilar material. The typical expansion joint is a flexible, watertight joint utilizing, backer rod and sealant. Expansion joints are typically 1/2 inch in width.

• Backwrapping. Where the foam substrate terminates, it should be backwrapped, in order to provide for proper protection of the foam. Backwrapping also provides for improved attachment of the substrate to the sheathing.

• Horizontal Surfaces: Trim Bands Quoins. There should be no horizontal (flat) surfaces. All surfaces should slope away from the structure.

NATIONAL ASSOCIATION OF HOME BUILDERS - Standards and Regulations

Exterior insulation and finish systems (EIFS) are multi-layered exterior wall systems used on both commercial buildings and homes. According to the DOE study, EIFS perform better that brick, stucco, and cement fiber siding in tests measuring the key building performance goals of energy efficiency, temperature control and moisture control in mixed, coastal, Zone 3 climates.

In addition, EIFS offer more design flexibility than other cladding products. 

Developed in Europe in the 1950s, EIFS were introduced in the U.S. almost 40 years ago. They were first used on commercial buildings and later on homes. Today, EIFS account for nearly 30% of the U.S. commercial exterior wall market.

EIFS typically consist of the following components:

• Insulation board, made of polystyrene or polyisocyanurate foam, which is secured to the exterior wall surface with a specially formulated adhesive and/or mechanical attachment;
• A durable, water-resistant base coat, which is applied on top of the insulation and reinforced with fiber glass mesh for added strength
• An attractive and durable finish coat – typically using acrylic co-polymer technology – which is both colorfast and crack-resistant.

The results of the DOE studies conducted over three years by researchers from Oak Ridge National Laboratory also concluded that EIFS and drainage EIFS performed better than the other typical exterior claddings (e.g., brick, stucco and cement fiber siding) in moisture resistance and insulation.

Adding further validation to the study is EIFS inclusion in the 2009 International Building Code and International Residential Code (IBC/IRC). These model building codes are the foundation for local building regulation around the U.S. and are a major influence on how buildings are constructed around the world.

The action by the ICC validates EIFS both as a product and as a process. It further removes any ambiguities in the interpretation of what EIFS are and how they are implemented into the building code construction process.