Exterior insulation finishing system
Exterior insulation and finishing system (EIFS) is a type of building exterior wall cladding system that provides exterior walls with an insulated finished surface and waterproofing in an integrated composite material system.
Although often called "synthetic stucco", EIFS is not stucco. Traditional stucco is a centuries-old material which consists of aggregate, a binder, and water, and is a hard, dense, thick, non-insulating material. EIFS is a lightweight synthetic wall cladding that includes foam plastic insulation and thin synthetic coatings. There are also specialty stuccos that use synthetic materials but no insulation, and these are also not EIFS. A common example is what is called one-coat stucco, which is a thick, synthetic stucco applied in a single layer (traditional stucco is applied in 3 layers). There is also an EIFS-like product called a direct-applied finish system (or DAFS), which is essentially an EIFS but without the insulation, and has quite different characteristics.
EIFS are proprietary systems of a particular EIFS producer and consist of specific components. EIFS are not generic products made from common separate materials. To function properly, EIFS needs to be architecturally designed and installed as a system.
There are a number of versions of EIFS. The most basic and common EIFS is called a barrier EIFS (also known as a traditional or conventional EIFS). Another type is called an EIFS with drainage, which is a barrier EIFS to which a water drainage capability has been added.
A basic EIFS includes only the insulation and EIFS materials (coatings, adhesives, etc.). Other types of EIFS may also include plastic edge trim, water-resistive barriers, a drainage cavity, and other accessories. The technical definition of "an EIFS" does not include wall framing, sheathing, flashings, caulking, water barriers, windows, doors, and other wall components. However, as of recently, architects have begun specifying flashings, sealants, and wiring fasteners (such as Viperstrap) as being a part of the EIFS scope of work, essentially requiring EIFS contractors to carry out that work as well. The technical national consensus standard for the definition of an EIFS, as published by ASTM International organization, does not include flashing or sealants as part of the EIFS. Many of the EIFS manufacturers have their own standard details showing typical building conditions for window and door flashings, control joints, inside/outside corners, penetrations, and joints at dissimilar materials which should be followed for that manufacturers warranty.
How EIFS is installed
EIFS is typically attached to the outside face of exterior walls with an adhesive (cementitious or acrylic based) or mechanical fasteners. Adhesives are commonly used to attach EIFS to gypsum board, cement board, or concrete substrates. EIFS is attached with mechanical fasteners (specially designed for this application) when installed over sheet-good weather barriers such as are commonly used over wood sheathings. The supporting wall surface should be continuous (not "open framing") and flat.
Next Generation EIFS
EIFS before 2000 was a barrier system, meaning the EIFS system itself was the weather barrier. After 2000 the EIFS industry introduced the air/moisture barrier that resides behind the foam. In a study done by the The Department Of Energy's Office of Science - Oak Ridge National Laboratory it was found that the best air/moisture barrier was a fluid barrier. The Oak Ridge National Laboratory, ATLANTA, Oct. 28, 2006 — EIFS "outperformed all other walls in terms of moisture while maintaining superior thermal performance." The National Institute of Standards and Technology (NIST) have evaluated the 5 life cycle stages of the environmental impact of EIFS alongside brick, aluminum, stucco, vinyl, and cedar. Depending on a variety of site and project specific conditions, EIFS has the potential to save money in construction costs and contribute toward energy efficient operations and environmental responsibility when correctly designed and executed.
Composition and types of EIFS
EIFS consists of a number of layers that are installed in the following order. The most basic EIFS (a barrier EIFS) consists of 3 layers:
- A layer of foam plastic insulation (also called simply "foam") that comes in the form of sheets 2' x 4'. If an adhesive is used to attach the insulation, the adhesive is applied to the foam with a trowel. Most EIFS use a type of insulation called Expanded Polystyrene, also known as EPS. EPS is 1 lb. density Expanded Polystyrene, similar to the white foam that coffee cups are made of. The usual range of thickness for EIFS insulation is 3/4" to 4", although thicker pieces are sometimes used for decoration accents – called foam shapes.
- A reinforced layer that is applied onto the face of the insulation with a trowel, consisting of a fiberglass reinforcing mesh ( or "mesh") embedded in a cementitous adhesive. The mesh has an open weave, somewhat like window screening but with opening about 1/4" square. It is made of fiberglass and can be cut with a utility knife. The mesh is available in various weights, the "heaviness" determines the impact strength of the surface (resistance to damage by being "hit"). The standard weight is 4oz, the high-impact mesh weight goes up to 15 or 20oz. This 2-part layer is called the Base Coat.
- A final topcoat,or finish, which is a colored, textured paint-like material that is applied with a trowel or, very rarely, by spraying. A wide range of colors and textures are available as well as custom colors. Available textures include smooth surfaces, rough "stucco-like" textures, embedded stone chips, multi-color (granite-like mixtures,) and even brick-like treatments. This layer is called the finish. It is acquired by floating.
If an EIFS with Drainage, or water-managed EIFS is installed, a water resistive barrier (aka a WRB) is first installed over the substrate (generally DensGlas Gold, exterior-grade gypsum sheathing, OSB or plywood). The moisture barrier is applied to the entire wall surface with a mesh tape over joints and a liquid-applied membrane or a protective wrap like Tyvek or felt paper. Then a drainage cavity is created (usually by adding some sort of space between the foam and the WRB). Then the other 3 layers, described above, are added. This type of EIFS is required by many building codes areas on wood frame construction, and is intended to provide a path for incidental water that may get behind the EIFS with a safe route back to the outside. The purpose is to preclude water from damaging the supporting wall.
Adhesives and Finishes are water-based, and thus must be installed at temperatures well above freezing. Two types of Adhesives are used with EIFS: those that contain Portland Cement ("cementitious"), or do not have any Portland Cement ("cementless"). Adhesives that contain Portland Cement harden by the chemical reaction of the cement with water. Adhesives and Finishes that are cementless harden by the evaporation of water – like house paint. Adhesives come in two forms. The most common is in a plastic pail as a paste, to which Portland Cement is added. Adhesives are also available as dry powders in sacks, to which water is added. Finishes come in a plastic pail, ready to use, like paint. EIFS insulation comes in individual pieces, usually 2' x 4', in large bags. The pieces are trimmed to fit the wall at the construction site.
History of EIFS
EIFS was developed in Europe after World War II and was initially used to retrofit solid masonry walls. EIFS started to be used in North America in the 1960s, and became very popular in the mid- 1970s due to the oil embargo and the resultant surge in interest in high energy efficiency wall systems (such as EIFS provides). The use of EIFS over stud-and-sheathing framing (instead of over solid walls) is a technique used primarily in North America. EIFS is now used all over North America, and also in many other areas around the world, especially in Europe and the Pacific Rim.
In North America, EIFS was initially used almost exclusively on commercial buildings. As the market grew, prices dropped to the point where its use became widespread on normal single family homes.
In the late 1980s problems started developing due to water leakage in EIFS-clad homes and buildings. This created an international controversy and numerous lawsuits. Critics argue that, while not inherently more prone to water penetration than other exterior finishes, barrier-type EIFS systems (non-water-managed systems) do not allow water that may penetrate the building envelope to escape.
The EIFS industry has consistently maintained that the EIFS itself was not leaking, but rather poor craftsmanship and bad architectural detailing at the perimeter of the EIFS was what was causing the problems. The building codes reacted by mandating EIFS with Drainage on wood frame building and additional on-site inspection.
Most homeowner insurance policies cover EIFS and EIFS-like systems. Insurance companies may not provide fire insurance coverage to clients who install EIFS exterior building systems, due to the lack of adequate fire-resistance inherent in the materials. Also, some facility owners have found that EIFS systems that are installed at lower building levels are subject to vandalism as the material is soft and can be chipped or carved resulting in significant damage.
EIFS installation was found to be a contributing factor in the multi-billion dollar problem known as the "Leaky condo crisis" in southwestern British Columbia and the "Leaky homes" issue in New Zealand that emerged separately in the 1980s and 1990s.
EIFS systems have been the subject of several lawsuits, mostly related to the installation process and failure of the system causing moisture buildups and subsequent mold growth. The most notable case concerned the former San Martin, California courthouse. This case was settled for 12 million dollars.
The basic underlying problem behind EIFS litigation was that EIFS was marketed as a cost-effective replacement for stucco. Stucco is expensive to install because it cracks over time. Stucco must be carefully applied by skilled craftsmen so that the cracks which will inevitably develop are subtle and not obvious. General contractors switched to EIFS because it was supposed to be easy to install with unskilled or semi-skilled labor and would not crack like traditional stucco. Although EIFS if properly installed according to the manufacturer's directions should not have water intrusion problems, many GCs cut corners by using unqualified labor (that is, illiterate laborers unable to read or follow directions) and also failed to adequately supervise their work. In turn, thousands of EIFS installations were noncompliant and suffered severe water intrusion and mold as a result. While the EIFS industry has consistently tried to shift the blame to GCs, the construction industry has retorted that using professional unionized journeymen carpenters in turn eliminates the cost advantage of EIFS over stucco, and that the EIFS industry should have anticipated this issue and engineered its products from the beginning to be installed by unskilled labor or semi-skilled labor (that is, it should have been a fault-tolerant design).
Marketing of EIFS and the EIFS industry
EIFS accounts for about 10% of the US commercial wall cladding market. There are several dozen EIFS producers in North America. Some sell nationwide, and some are regional in their area of business operations. The EIFS producers sell the various system components (adhesives, coatings, etc.) through specialty building product distributors who in turn resell the components to local EIFS installers. The top 5 EIFS producers account for about 90% of the US market. These producers include Dryvit Systems, STO Corp., BASF Wall Systems (Senergy, Finestone, SonoWall and Acrocrete), Master Wall, and Parex.
EIFS architectural details
Another benefit of EIFS is the option to add architectural details that are composed of the same materials. EIFS mouldings or as they are commonly referred to, stucco mouldings, come in a large variety of shapes and sizes. They are widely used on residential/commercial projects in North America and are gaining popularity worldwide. Production methods have come a long way since their inception which allow manufacturers to create with great efficiency in a cost effective manner. The production of architectural foam mouldings was recently showcased on How It's Made airing on The Discovery Channel Network.
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- "AnimasInsurers Slapping EIFS Exclusions on Insurance Policies". Associated Construction Publications.
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- Leaky Buildings, New Zealand Parliament, 06 November 2002. Retrieved 2013-11-13