Exterior Insulation and Finish Systems (EIFS) are well known in the art. Such systems typically consist of a layer of substrate such as plywood, oriented-strand board OSB, gypsum sheathing etc, an insulation layer such expanded polystyrene, mesh embedded in a coat of polymer modified cement and polymeric finish. Originally, EIFS was an exterior wall concept designed to have high insulation values and a reliable stucco finish that could be economically created in a wide array of textures and colors. Generally, these systems include an exterior wall having an expanded polystyrene foam insulation board EPS, attached via an adhesive or mechanical fasteners to the substrate. The exterior of the insulation, after all details specified by architect such moldings, bands, structural or aesthetical joints are created, is covered with a durable water resistant basecoat, which receives a fiberglass mesh as reinforcement. A durable finish coat, typically using an acrylic co-polymer technology, is then applied. The finish coat is generally both color fast and crack resistant.
EIFS, which is a type of cladding for exterior building walls, is defined per ASTM E631-91B as a: non-loading outdoor wall finish system consisting of a thermal insulation board, an attachment system, a reinforced basecoat, exterior joint sealant, and a compatible finish.
While such EIFS have proved to be quite satisfactory for ease of installation, insulating properties, and ability to receive a variety of aesthetically pleasing finishes, a serious and vexing problem associated with EIFS construction exists. This problem is one of water accumulation behind the exterior wall covering. Such water it's considerate to be the result of condensation and wind-driven water that may enter behind the exterior wall covering at any point where the exterior surface of the coating is penetrated. Moisture is driven through the porosity of exterior polymer cement and finish coat surface and through air-permeable insulation (EPS) by the difference pressure of cold air and hot air. The air-permeable insulation is exposed to permit air to flow into and out of the insulation layer, to equalize the pressure of exterior environment and inside cavity of wall. This flux of air will drive moisture into the system. Wind-driven water that may enter behind the exterior wall covering may be the result of poor workmanship or design, deterioration of flashing or sealants over time, lesser quality doors and windows, or any other penetration or compromise of the exterior finish.
Once inside the sealed wall and behind cladding, the water can remain trapped long enough before evaporating to damage or rot any water sensitive elements to which the insulation is bonded, including framing structure. This water is known in the art as intruding or incidental water.
To eliminate those inconveniences, the EIFS industry created drainable systems. Drainage is accomplished by means of channels formed by vertical ribbons of adhesive applied to the back of the insulation boards or channeled EPS boards to form channels for incidental moisture to escape. The moisture and intruding water travels between the ribbons to the bottom termination of the system where it escapes through weep holes of the drainage vented track. This system is installed over a water and moisture resistive barrier.
Drainable systems have difficulties when it needs to drain water among windows, and when vertical walls end with ceiling or beam. Soffits have no solutions to drain condensation water. In addition, the moist environment is a breeding ground for wood consuming insects and health hazards such as various varieties of molds. Attempts have been made to prevent entry of moisture into the building wall interior by sealing or caulking entry points in and around wall components as the primary defense against moisture intrusion, or by installing flashing around the wall components to divert the moisture. These attempts have not been completely successful. Sealants are not only difficult to properly install, but tend to deteriorate and separate from the wall components due to climatic conditions, building movement, the surface type, or chemical reactions. Flashing is also difficult to install and may tend to hold the moisture against the wall component. Flashings are thermal bridges from outside temperatures and sources of airflow into the wall cavity. These materials are of no value in addressing the problem of moisture that has already entered a building wall cavity or moisture that penetrate the permeable EPS board and condensate on the moisture barrier surface.
The superior energy efficiency and design flexibility of EIFS have resulted in growing popularity, but the presence of moisture remains a vexing problem. Thus, there is a great need for a system and method to prevent and stop moisture to penetrate the insulation layer and intersections of EIFS whit other elements.
For that, we have to fully understand the phenomenology of interior and exterior environment difference, such as temperature, relative humidity and pressure, the conditions of condensation and physical properties of materials such permeability, permissively, thermal conductibility and others.
That part of any building that physically separates the exterior environment from the interior environment is called the building enclosure or building envelope. Also, the building enclosure may contain, but is not the same as, the so-called thermal envelope, term that is used to refer to the thermal insulation within the enclosure. The overall enclosure is made up of all the contiguous enclosure sub-assemblies. Further down, NP-EIFS is considered the thermal envelope of the enclosure.
Building assemblies need to be protected from wetting via rainwater, groundwater, air transported water and vapor diffusion. The typical strategies use drainage planes on air barriers, air pressure control installed between insulation system and exterior wall assembly indifferent of climate location and season. Moisture usually moves from warm to cold, driven by the thermal gradient (vapor pressure differential), and from more to less, driven by the concentration gradient. In cold climates, moisture from the interior flows towards the exterior by passing through building enclosure, in hot climates, moisture from the exterior flows towards the cooled interior by passing through the building envelope. By climates and seasons we can have two extreme situations from the exterior environment: very cold and dry, and hot-humid, with the same inside conditioned space, limited to 60% relative humidity at 75° F. (23.8° C.), both applied to a building having drainage EIFS cladding.
In cold climates, moisture from interior flows towards the exterior, driven by a high vapor differential pressure between interior (75° F. Temperature, 60% Relative Humidity), and exterior (−4° F. Temperature, 30% RH). Absolute humidity (water vapor concentration) is the driving force. Water vapor molecules will wend their way through porous materials until they reach the moisture barrier. In cold and very cold climates, condensation on interior surfaces occurs during the heating season because the interior surfaces of exterior walls are cool from heat loss. Because, on this situation, EIFS is placed on the cold side of building, the wall assembly is warm, including vapor retardant material of moisture barrier. This will equilibrate temperatures, air pressure and relative humidity from inside conditioned environment and wall cavity. Condensation is avoided by reducing water vapor entering the building components and preventing it from dropping below the dew point. Theoretic, if insulation thickness is in accordance with local climate, the only reason of condensation is the thermal bridges around windows, doors, flashings and other outside penetrations. Practically, any material with high conductibility or air leakage from outside can cause condensation.
In hot-humid climates and seasons, moisture from the exterior flows towards the cooled interior by passing through the building enclosure, condensation occurs because interior surfaces are typically cold and subsequently accessed by moisture levels, which are too high. Vapor is driven inward through building cladding by a high vapor pressure differential between exterior hot and humid air (120° F.; 100% Relative Humidity; 11.74 kPa Vapor Pressure) and interior wall assembly (75° F.; 60% RH; 1.82 kPa VP), cooled by inside air conditioning. The cold surfaces in hot climates arise from the air conditioning of enclosures. When exterior hot air is cooled, its relative humidity increases. If the exterior hot air is also humid, cooling this air will typically raise its relative humidity above the dew point. When cladding is drainage EIFS, vapors are driven from outside hot environment through exterior surface of the coating which is porous, and through expanded polystyrene foam (EPS) used as insulation which is permissive to vapors, and will condensate on the cold surfaces of moister retardant material, used as air and water barrier. This is the condensation surface, which became the drainage plane. Cooling the enclosure and the exterior sheathing substrate from inside conditioned space, and moisture contact with this surface, will create most propitious conditions for condensation behind EIFS cladding. In the summer time, we have the opposite situation from winter, when the insulation is placed in the warm side of the wall. The wall assembly is not properly protected from inside heat loss (cold loss), because the wall assembly materials are thermal conductive, metal or wood studs become thermal bridges, and fiberglass insulation from inside of the wall cavity is too permissive to air pressure differential between cold and hot. That is, in regions with varying climatic temperatures, the location where the dew point occurs and where the resulting moisture condensation forms in the building enclosure varies.
Accordingly, one of the most practical solutions in controlling condensation and mold behind EIFS and inside enclosure in all climates is limiting hot and humid exterior air or other forms of moisture transport from contacting the moisture retardant material used as air barrier, the condensation surface. Controlling the vapor pressure at this surface is the most commonly facilitate to maintaining the conditioned space at a slightly positive air pressure to the exterior (approximately 2, 3 Pa). Pressurization of building enclosure is expedited by airtight construction: 2.00 l/(s-m2) @75 Pa.
The present invention relates to an EIFS cladding, having two air and vapor barriers. First air-vapor barrier is the classical weather barrier that guard sheathing from incidental moisture, improved to be Class 1 Impermeable (0.1 Perm), test procedure for vapor retarders: ASTM E-96 Test Method A. The moisture retardant material used as air barrier must be a continuous air and moisture barrier, a liquid membrane applied to the substrate, the entire inner layer of NP-EIFS. Second, the air-vapor and watertight barrier is even the insulation layer. The NP-EIFS foreseen the outer insulation layer to be closed cell extruded polystyrene thermal board XPS, which is a material with minimum of water absorption and vapor permeance. Rigid closed cell extruded polystyrene XPS is conforming to the following properties, per inch (25 mm) thickness: Thermal Resistance. R-Value 5.0 (ft2h° F./Btu) min. at 75° F. Mean Temperature (ASTM C-518); Water Absorption 0.1% by volume, max. (ASTM C-272); Water Vapor Permeance 0.8/0.2 perm (ng/Pasm2) (ASTM E-96): no capillarity. The variability observed in data obtained from testing laboratories using ASTM E-96 has recently become a concern. Although, most laboratories are performing analyses in accordance to the test method, the interpretation of the method has resulted in a variety of techniques for sample assembly and data evaluation. Vapor Permeance (Tendency of material to allow water vapor to diffuse through it) or Water Vapor Transmission is dependent on thickness of material. For 1½ inch (38 mm). XPS can be considered an air and vapor barrier. The classical EIFS uses as insulation expanded polystyrene boards EPS, which is on Class 3, Semi Permeable (1.0-10 Perm) or extruded polystyrene boards (EMS Class PM) but not assembled to be an air-vapor barrier for exterior environment.
Air and moisture barriers are systems of materials designed and constructed to control air and vapor flow between the conditioned space and unconditioned space. Air barrier systems are assembled from materials, incorporated in assemblies that are interconnected to create enclosures. Each of the three elements has measurable resistance to air flow. The minimum resistance or air permeances for the three components are specified in the art: Material 0.02 l/sm2; Assembly 0.20 l/sm2; Enclosure 2.00 l/sm2; at 75 Pa.
It is therefore an object of the invention to provide a method and technology of application of materials, to create an assembly with similar vapor permeance and airflow resistance as the materials components. Moisture retardant properties of XPS will be extended to the entire wall assembly, creating a Non-Permissive to water, air and vapor thermal building envelope of the enclosure.
Another object of the invention is to provide waterproof and air/vapor-proof details, using patented closed cell, expanding polyurethane foam to fill all spaces between insulation and intersections. Also, invention presents a new concept of flashing and sealant application around windows/doors and other constructive elements to avoid thermal bridges and air leakage inside thermal envelope and inside wall assembly. The Non-Permissive thermal envelope assembly will be combined with the intersections of construction elements and terminations, to create Non-Permissive enclosures.
A still further object of the invention is to provide a waterproofing, vapor barrier and air leakage rates similar to Class 1 Impermeable, inside EIFS cladding, with chipping the standard of the industry by fulfilling requirements for design freedom, and increasing energy efficiency, weather ability, durability and beauty, with similar cost effectiveness.
NP-EIFS is a Class PM (polymer modified) system, which offers high impact protection, excellent energy savings and a durable, aesthetically pleasing finish.
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