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A Look at Exterior Insulation and Finish Systems

EIFS: A Starting Point

Exterior Insulation and Finish Systems (EIFS), commonly known as synthetic stucco, is an exterior cladding system composed of an adhesively or mechanically fastened foam insulation board, reinforcing mesh, a base coat, and an outer finish coat. EIFS is available in various colors and external textures designed to look like traditional stucco. Its exterior appearance looks almost identical to conventional stucco, although conventional stucco is comprised of multiple layers of cement over a wire mesh.

EIFS: System Appeal

Home purchasers are attracted to EIFS because of its majestic look. The exterior cladding makes normal homes stand out and delivers fantastic curb appeal.

Architects and builders are attracted to EIFS because the expanded polystyrene (EPS) insulation used in this product is easily shaped and sculpted. The EPS insulation can be used for making decorative bands, quoins, and other adornments on homes. In addition, EIFS is a competitively priced alternative to conventional stucco or brick siding.

EIFS is also popular because it acts as a great insulator. Besides offering design flexibility, EIFS insulation boards can cover a building’s entire exterior wall space, in essence eliminating any thermal breaks in the insulation barrier. This can reduce energy consumption, reduce air infiltration and increases interior comfort..

EIFS: System History

EIFS was developed in post-World War II Germany to repair war-ravaged structures as well as address the energy consumption caused by lack of insulation in masonry structures.

Insulating a building traditionally takes place by placing an insulating material into the wall cavity. It was discovered that insulating a building from the outside would be more energy efficient, since insulating from the inside leaves thermal breaks in the insulation where the wall stud exists.

Wood framed homes have a wall cavity between the drywall and exterior siding. These homes reduce their energy costs by filling the wall cavity with insulation. When EIFS was developed, it made insulating a building from the outside possible by attaching sheets of foam insulation over the entire exterior, thus eliminating any thermal breaks. This allowed Europeans to reduce their energy consumption as well as beautify their homes.

Dryvit Systems, Inc. introduced EIFS into the United States in 1969. With the onset of the energy crisis during the early 1970s, EIFS became popular among energy-conscientious architects and builders. During the energy crisis, many U.S. and European manufacturers entered the EIFS market place.

EIFS was first introduced to the commercial market-high-rise condominiums, office buildings and stores were the first buildings clad with EIFS. It was not widely used in residential construction until the mid-1980s.

EIFS manufacturers began marketing EIFS to the residential market in conjunction with the increase in housing starts that began in the mid-1980s. Touting energy efficiency, design flexibility and curb appeal, EIFS manufacturers successfully marketed their product line to high-end builders. During the 1980s, EIFS became a cladding of choice for many higher-priced residential homes.

EIFS: Discovery of System Problems

The problem with barrier-type EIFS cladding is that the systems rely entirely on their outside surface to prevent water penetration and moisture intrusion. Barrier EIFS does not have internal drainage provision, and therefore requires excellent design and workmanship to produce a weather-tight and long-lasting system. Throughout the United States, a significant percentage of homes clad with barrier-type EIFS are experiencing problems with water penetration and moisture intrusion, primarily around windows, doors, and roof-to-sidewall intersections where kick-out flashing is necessary. The retention of moisture in these systems for an extended period of time invariably leads to damage that frequently goes undetected for an extended period of time. In many homes clad with barrier EIFS, water that enters behind cladding does not evaporate, or “escape,” quickly enough to allow structural members to dry out. The moisture content and temperature inside the wall cavities of these homes often promote rapid growth of wood destroying fungus, leading to deterioration or rot of the sheathing/substrate. Depending on the size of the home, EIFS repairs can range from tens of thousands to over one hundred thousand dollars.

In contrast to residential construction, most high-rise condominiums, office buildings, and stores are made of concrete and steel. While problems with barrier-type EIFS have also been widely reported on these structures, such problems have generally taken a longer period of time to manifest then is the case with wood-framed residential construction.

The New Hanover County (North Carolina) Inspections Department investigated its first barrier-type EIFS home in November 1994 in response to a homeowner complaint. Thirty-one homes were subsequently inspected in July and August 1995, and moisture problems existed in all but two houses. The homes that were inspected were in different subdivisions and involved different contractors and different manufacturer systems.

News reports of moisture entrapment problems associated with EIFS in residential construction in the Wilmington, North Carolina area prompted additional testing and studies of barrier-type EIFS homes in Wilmington and other areas in North Carolina in the fall of 1995. These tests and studies were conducted by several organizations, including the North Carolina Home Builders Association, the American Institute of Architects (AIA), and the EIFS Industry Members Association (EIMA). The tests and studies revealed that many of the more than 200 homes tested had developed moisture problems inside exterior walls that, in some cases, caused extensive damage.

EIFS: Problems Limited to Wilmington, North Carolina?

The problems associated with barrier-type EIFS in residential construction first came to light in Wilmington, North Carolina, where inspectors began acting upon an unusually high number of homeowner complaints concerning water damage to their EIFS homes. However, home inspectors throughout the country now point out that similar problems are being discovered in a number of states, including Alabama, Colorado, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Missouri, New Jersey, New York, North Dakota, Ohio, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Utah, Virginia, and Washington. Problems have also been discovered throughout Canada, notably Vancouver, British Columbia and Saskatchewan.

The EIFS industry, as represented by the EIFS Industry Members Association (EIMA), initially characterized the problems with barrier EIFS in Wilmington as “unique” and an “isolated problem.” Assumptions were made that, due to a unique set of circumstances, moisture was able to find its way into homes in coastal regions that featured high levels of humidity or sustained periods of rainfall. When reports of similar problems surfaced in other areas of North Carolina as well as other states, the North Carolina Office of the Attorney General directed builders, developers and real estate agents to provide a disclosure form to prospective purchasers of EIFS-clad homes before any serious negotiations begin. The North Carolina Association of Realtors® EIFS Disclosure Statement states the following:

The house you are considering purchasing is clad with a product known as exterior insulation and finishing system (“EIFS, also referred as “synthetic stucco”). You should be aware that tests performed on a number of EIFS-clad homes in certain parts of North Carolina have revealed moisture-related problems. In Wilmington, 90 percent of the homes tested by local architects and home inspectors exhibited problems. Testing has shown that moisture entering the wall cavities may become trapped behind the EIFS exterior. In some cases, the trapped moisture has caused substantial damage, including rot, to underlying wood sheathing and framing members. In other cases, little or no damage has been observed.

Legal responsibility for correction of the observed problems has yet to be determined. Several class action lawsuits have been filed by homeowners against certain EIFS manufacturers. In addition, several individual lawsuits against builders, manufacturers and trades men known as EIFS applicators have been filed in the Wilmington area. These lawsuits are currently pending.

On March 12, 1996, the North Carolina Building Code Council adopted stringent guidelines for the application of EIFS to new residential structures and for any repairs of existing EIFS-clad houses with moisture damage problems. The Council is expected to tighten these requirements further by mandating that drainage systems be installed in the exterior walls of all EIFS-clad homes constructed in the future.

Before deciding to buy, you may want to have the house tested by a qualified moisture intrusion expert using EIFS testing guidelines available from the North Carolina Department of Insurance’s Engineering Division (919) 733-3901.

EIFS: Causes of System Problems

Deviation from installation guidelines
EIFS application requires strict observance of manufacturer recommended specifications and guidelines and involves meticulous workmanship and attention to detail. When improperly applied, the EIFS cladding does not perform its intended function and allows water to infiltrate behind the cladding, where it becomes trapped.

EIFS details are procedures outlined by the EIFS manufacturer that provide guidance to the architect, builder and applicator as to the proper installation of the product. All EIFS manufacturers have details and procedures that builders and applicators are expected to follow. Installation details are typically very similar among EIFS products and EIFS manufacturers, but there are differences.

EIFS must be purchased from an EIFS distributor. The manufacturer or distributor trains applicators and issues certificates stating that the applicator has been properly trained. It is the responsibility of the distributor to ensure that EIFS is sold only to those certified applicators.

 

Foam insulation placed below grade
Prior to recent building code changes, the expanded polystyrene (EPS) 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 termite infestations. Often times, the first indication that an infestation problem exists is a swarm of termites. This swarm occurs either inside the structure or close to the outside of the home. Other indications of infestation problems are mud tubes or galleries of mud on a foundation wall. 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, the termites tunnel galleries in the wet foam and establish themselves inside the home. In those instances where the foam retains moisture and does not dry out, termites are able to break their contact with the ground and exploit the moisture source above ground.

Another problem with placing the foam below grade is the ability of water vapor to migrate upwards through the EPS 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.

 

Missing secondary weather barrier and inability to drain
Most wood-framed residential homes require a secondary weather barrier to be placed over the sheathing before the exterior cladding is installed. This barrier protects the home from incidental water intrusion and allows moisture to exit the home by travelling on top of the barrier, keeping the sheathing and structural members relatively dry. Eliminating a barrier and rendering a substrate unprotected invites trouble, no matter what type of exterior cladding is used.

Due to the design of the EIFS, a majority of EIFS clad homes do not have a secondary weather barrier placed over the exterior sheathing. A large number of EIFS applications use an adhesive to fasten the two-foot by four-foot insulation boards to the sheathing. If an adhesive is used to hold the insulation boards to the sheathing, then a secondary weather barrier cannot be used. Any water that infiltrates the system will become trapped between the EIFS and the sheathing.

It is estimated that 95 percent of homes clad with EIFS in the United States are barrier-type. Most barrier EIFS projects are adhesively applied because it is less time consuming to install. Adhesively applied EIFS prohibits a vapor barrier from being installed. It also prevents many self-flashing windows from being installed properly since the sill flashing must be cut off to accommodate the adhesively attached foam board.

Divided responsibilities
An EIFS applicator is responsible for the application process-attaching the foam insulation to the substrate, applying the fiberglass mesh, embedding the fiberglass mesh with base coat and applying a finish coat. Many details outlined by manufacturers require the services of other tradesmen. A typical EIFS applicator does not install backer rods and sealant, but should install the EIFS so that it is possible to install these critical components. The builder is responsible for subcontracting the backer rod and sealant components. Flashing around windows, doors, decks, chimneys and roofs is the responsibility of the builder and his roofer. The applicator should recognize improper flashing and not continue the application process until the problem is corrected. According to the National Association of Home Builders Research Center, “This divided responsibility combined with the need for special construction details are alleged as the causes of premature failure” of EIFS.

Other contributing factors
Many homes have been constructed with an interior poly-vapor-barrier. A plastic sheet covers the interior wall studs and insulation behind the drywall. This barrier reduces the wall’s ability to dry. According to the NAHB Research Center, “The poly-vapor-barrier increases drying time in a wall with EIFS cladding by approximately eight-fold.”

Leaking windows, which allow moisture to enter behind the cladding, have also been documented as a problem. 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.

Pressure differentials

Barrier EIFS is a face-sealed system. The system relies on a water and airtight seal over the entire wall system. When this is achieved, an air cavity is created between the exterior sheathing behind the EIFS and the interior of the home. Positive air pressure changes caused by wind on the exterior of the home create a negative pressure in the wall cavity. Any breach in the barrier EIFS system will force air through that opening and into the wall cavity. When rain is introduced in this scenario, water, not air, is forced through any breach in the barrier EIFS. Many researchers indicate that the difference in pressure differentials is responsible for the majority of the water intrusions in face-sealed systems.

Other wall claddings such as brick, lap siding, shingles and traditional stucco allow air to infiltrate, thus rendering the positive force applied to the building balanced.

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