Curtain wall is a term used to describe a building façade which does not carry any dead load from the building other than its own dead load. A facade or façade (fəˈsɑːd is generally one side of the exterior of a Building, especially the front but also sometimes the sides and rear Dead and Live loads are terms used in mechanical and Structural engineering, especially where analysis of real world objects is required These loads are transferred to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, wind forces acting on the building, seismic forces (usually only those imposed by the inertia of the curtain wall), and its own dead load forces. A wall is a usually solid structure that defines and sometimes protects an area Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes
Curtain walls are typically designed with extruded aluminium members, although the first curtain walls were made of steel. The aluminium frame is typically infilled with glass, which provides an architecturally pleasing building, as well as benefits such as daylighting. Daylighting is the practice of placing Windows or other transparent media and reflective surfaces so that during the day natural light provides effective internal illumination However, parameters related to solar gain control, such as thermal comfort and visual comfort are more difficult to control when using highly-glazed curtain walls. Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment (ASHRAE Standard 55 Other common infills include: stone veneer, metal panels, louvers, and operable windows or vents. Infill in its broadest meaning is material that fills in an otherwise unoccupied space
Curtain walls differ from storefront systems in that they are designed to span multiple floors, and take into consideration design requirements such as: thermal expansion and contraction; building sway and movement; water diversion; and thermal efficiency for cost-effective heating, cooling, and lighting in the building. A tuned mass damper, also known as an active mass damper ( AMD) or harmonic absorber, is a device mounted in structures to prevent discomfort damage or
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History
Medieval curtain wall
A Curtain wall is used to describe the set of walls that surround and protect the interior (bailey) of a medieval castle. A castle is a defensive structure seen as one of the main symbols of the Middle Ages. These walls are often connected by a series of towers or mural towers to add strength and provide for better defense of the ground outside the castle, and are connected like a curtain draped between these posts. A curtain (in the US also known as a drape or drapery) is a piece of Cloth intended to block or obscure Light, or Drafts, or Additional provisions and buildings were often enclosed by such a construction, designed to help a garrison last longer during a siege by enemy forces. Garrison (various spellings (from the French garnison, itself from the verb garnir, "to equip" is the collective term for a body of Troops Examples of curtain walls as part of castles are at Muchalls Castle, Scotland and Dunstanburgh Castle, England, the latter of which is in a ruined state. Muchalls Castle stands overlooking the North Sea in the countryside of Kincardine and Mearns, Aberdeenshire, Scotland. Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. Dunstanburgh Castle lies on a spectacular headland on the coast of Northumberland in northern England, between the villages of Craster and Embleton England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland
Modern curtain wall
Prior to the middle of the nineteenth century, buildings were constructed with the exterior walls of the building (bearing walls, typically masonry) supporting the load of the entire structure. The development and widespread use of structural steel and later reinforced concrete allowed relatively small columns to support large loads and the exterior walls of buildings were no longer required for structural support. The exterior walls could be non-bearing, and thus much lighter and more open than the masonry bearing walls of the past. This gave way to increased use of glass as an exterior façade, and the modern day curtain wall was born.
The first curtain walls were made with steel mullions, and the plate glass was attached to the mullions with asbestos or fiberglass modified glazing compound. A mullion is a structural element which divides adjacent Window units Eventually silicone sealants or glazing tape were substituted. Silicones are largely inert compounds with a wide variety of forms and uses A sealant is a viscous material that changes state to become solid once applied and is used to prevent the penetration of Air, Gas, Noise, Dust Some designs included an outer cap to hold the glass in place and to protect the integrity of the seals. The first curtain wall installed in New York City was this type of construction. Lever House, designed by Gordon Bunshaft of Skidmore Owings and Merrill and located at 390 Park Avenue in New York City, is the quintessential The City of New York Earlier modernist examples are the Bauhaus in Dessau and the Hallidie Building in San Francisco. Modernism describes an array of Cultural movements rooted in the changes in Western society in the late nineteenth and early twentieth century ("House of Building" or "Building School" is the common term for the, a school in Germany that combined crafts and the fine arts and was famous Dessau is a town in Germany on the junction of the rivers Mulde and Elbe, in the Bundesland (Federal State of Saxony-Anhalt The Hallidie Building, is an office building in the Financial District of San Francisco California, at 130 Sutter Street, between Montgomery Street The City and County of San Francisco is the fourth most populous city The 1970’s began the widespread use of aluminum extrusions for mullions. Extrusion is a process used to create objects of a fixed cross-sectional profile Aluminum offers the unique advantage of being able to be easily extruded into nearly any shape required for design and aesthetic purposes. Today, the design complexity and shapes available are nearly limitless. Custom shapes can be designed and manufactured with relative ease.
Similarly, sealing methods and types have evolved over the years, and as a result, today’s curtain walls are high performance systems which require little maintenance.
- Stick systems
The vast majority of curtain walls are installed long pieces (referred to as sticks) between floors vertically and between vertical members horizontally. Framing members may be fabricated in a shop environment, but all installation and glazing is typically performed at the jobsite. Glazing is a transparent part of a Wall, usually made of Glass or Plastic ( acrylic and Polycarbonate)
- Unitized systems
Unitized curtain walls entail factory fabrication and assembly of panels and may include factory glazing. These completed units are hung on the building structure to form the building enclosure. Unitized curtain wall has the advantages of: speed; lower field installation costs; and quality control within an interior climate controlled environment. The economic benefits are typically realized on large projects or in areas of high field labor rates.
- Rainscreen principle
A common feature in curtain wall technology, the rainscreen principle theorizes that equilibrium of air pressure between the outside and inside of the "rainscreen" prevents water penetration into the building itself. For example the glass is captured between an inner and an outer gasket in a space called the glazing rebate. The glazing rebate is ventilated to the exterior so that the pressure on the inner and outer sides of the exterior gasket is the same. When the pressure is equal across this gasket water cannot be drawn through joints or defects in the gasket.
Design
Curtain wall systems must be designed to handle all loads imposed on it as well as keep air and water from penetrating the building envelope.
Loads
The loads imposed on the curtain wall are transferred to the building structure through the anchors which attach the mullions to the building. The building structure needs to be designed and account for these loads.
- Dead load
Dead load is defined as the weight of structural elements and the permanent features on the structure. In the case of curtain walls, this load is made up of the weight of the mullions, anchors, and other structural components of the curtain wall, as well as the weight of the infill material. Additional dead loads imposed on the curtain wall, such as sunshades, must be accounted for in the design of the curtain wall components and anchors.
- Wind load
Wind load acting on the building is the result of wind blowing on the building. This wind pressure must be resisted by the curtain wall system since it envelops and protects the building. Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Wind loads vary greatly throughout the world, with the largest wind loads being near the coast in hurricane-prone regions. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Building codes are used to determine the required design wind loads for a specific project location. A building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as Buildings and Nonbuilding Often, a wind tunnel study is performed on large or unusually shaped buildings. A wind tunnel is a research tool developed to assist with studying the effects of air moving over or around solid objects A scale model of the building and the surrounding vicinity is built and placed in a wind tunnel to determine the wind pressures acting on the structure in question. These studies take into account vortex shedding around corners and the effects of surrounding buildings. Vortex shedding is an unsteady flow that takes place in special flow velocities (according to the size and shape of the cylindrical body
- Seismic load
Seismic loads need to be addressed in the design of curtain wall components and anchors. In most situations, the curtain wall is able to naturally withstand seismic and wind induced building sway because of the space provided between the glazing infill and the mullion. Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes In tests, standard curtain wall systems are able to withstand three inches (75 mm) of relative floor movement without glass breakage or water leakage. Anchor design needs to be reviewed, however, since a large floor-to-floor displacement can place high forces on anchors. (Additional structure must be provided within the primary structure of the building to resist seismic forces from the building itself. )
- Snow load
Snow loads and live loads are not typically an issue in curtain walls, since curtain walls are designed to be vertical or slightly inclined. Dead and Live loads are terms used in mechanical and Structural engineering, especially where analysis of real world objects is required If the slope of a wall exceeds 20 degrees or so, these loads may need to be considered.
- Thermal load
Thermal loads are induced in a curtain wall system because aluminum has a relatively high coefficient of thermal expansion. WikipediaNaming When the Temperature of a substance changes the energy that is stored in the Intermolecular bonds between atoms changes This means that over the span of a couple of floors, the curtain wall will expand and contract some distance, relative to its length and the temperature differential. This expansion and contraction is accounted for by cutting horizontal mullions slightly short and allowing a space between the horizontal and vertical mullions. In unitized curtain wall, a gap is left between units, which is sealed from air and water penetration by wiper gaskets. A gasket is a mechanical seal that fills the space between two objects generally to prevent leakage between the two objects while under compression. Vertically, anchors carrying wind load only (not dead load) are slotted to account for movement. Incidentally, this slot also accounts for live load deflection and creep in the floor slabs of the building structure. Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses It occurs as a result of long term exposure to levels of
- Blast load
Accidental explosions and terrorist threats have brought on increased concern for the fragility of a curtain wall system in relation to blast loads. The bombing of the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma, has spawned much of the current research and mandates in regards to building response to blast loads. The Alfred P Murrah Federal Building was a United States Federal Government complex located at 200 N Oklahoma City is the capital and largest city of the US state of Oklahoma. Oklahoma ( is a state located in the South Central region of the United States of America. Currently, all new federal buildings in the U. S. , and all U. S. embassies built on foreign soil, must have some provision for resistance to bomb blasts.
Since the curtain wall is at the exterior of the building, it becomes the first line of defense in a bomb attack. As such, blast resistant curtain walls must be designed to withstand such forces without compromising the interior of the building to protect its occupants. Since blast loads are very high loads with short durations, the curtain wall response should be analyzed in a dynamic load analysis, with full-scale mock-up testing performed prior to design completion and installation. In physics the term dynamics customarily refers to the time evolution of physical processes
Blast resistant glazing consists of laminated glass, which is meant to break but not separate from the mullions. Laminated glass is a type of Safety glass that holds together when shattered. Similar technology is used in hurricane-prone areas for the protection from wind-borne debris. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding
Infiltration
Air infiltration is the air which passes through the curtain wall from the exterior to the interior of the building. The air is infiltrated through the gaskets, through imperfect joinery between the horizontal and vertical mullions, through weep holes, and through imperfect sealing. A mullion is a structural element which divides adjacent Window units The American Architectural Manufacturers Association (AAMA) is the governing body in the U. S. which sets the acceptable levels of air infiltration through a curtain wall. This limit is expressed (in America) in cubic feet per minute per square foot of wall area at a given test pressure. (Currently, most standards cite less than 0. 6 CFM/sq ft as acceptable).
Water penetration is defined as any water passing from the exterior of the building through to the interior of the curtain wall system. Sometimes, depending on the building specifications, a small amount of controlled water on the interior is deemed acceptable. To test the ability of a curtain wall to withstand water penetration, a water rack is placed in front a mock-up of the wall with a positive air pressure applied to the wall. This represents a wind driven heavy rain on the wall. Field tests are also performed on installed curtain walls, in which a water hose is sprayed on the wall for a specified time.
Deflection
One of the disadvantages of using aluminum for mullions is that its modulus of elasticity is about one-third that of steel. An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically (i This translates to three times more deflection in an aluminum mullion compared to the same steel section under a given a load. Building specifications set deflection limits for perpendicular (wind-induced) and in-plane (dead load-induced) deflections. It is important to note that these deflection limits are not imposed due to strength capacities of the mullions. Rather, they are designed to limit deflection of the glass (which may break under excessive deflection), and to ensure that the glass does not come out of its pocket in the mullion. Deflection limits are also necessary to control movement at the interior of the curtain wall. Building construction may be such that there is a wall located near the mullion, and excessive deflection can cause the mullion to contact the wall and cause damage. Also, if deflection of a wall is quite noticeable, public perception may raise undue concern that the wall is not strong enough.
Deflection limits are typically expressed as the distance between anchor points divided by a constant number. A deflection limit of L/175 is common in curtain wall specifications, based on experience with deflection limits that are unlikely to cause damage to the glass held by the mullion. Say a given curtain wall is anchored at 12 foot (144 in) floor heights. The allowable deflection would then be 144/175 = 0. 823 inches, which means the wall is allowed to deflect inward or outward a maximum of 0. 823 inches at the maximum wind pressure.
Deflection in mullions is controlled by different shapes and depths of curtain wall members. The depth of a given curtain wall system is usually controlled by the area moment of inertia required to keep deflection limits under the specification. The second moment of area, also known as the area moment of inertia or second moment of inertia, is a property of a shape that is used to predict its resistance to Another way to limit deflections in a given section is to add steel reinforcement to the inside tube of the mullion. Since steel deflects at 1/3 the rate of aluminum, the steel will resist much of the load at a lower cost or smaller depth.
Strength
Strength (or maximum useable stress) available to a particular material is not related to its material stiffness (the material property governing deflection); it is a separate criterion in curtain wall design and analysis. Stress is a measure of the average amount of Force exerted per unit Area. In Structural engineering, structural design is an Iterative process of applying Engineering mechanics and past experience to create a functional economic Structural analysis comprises the set of physical laws and mathematics required to study and predict the behavior of structures This often affects the selection of materials and sizes for design of the system. For instance, a particular shape in aluminum will deflect almost three times as much as the same steel shape for an equivalent load (see above), though its strength (i. e. the maximum load it can sustain) may be equivalent or even slightly higher, depending on the grade of aluminum. WikipediaNaming Because aluminum is often the material of choice, given its lower unit weight and better weathering capability as compared with steel, deflection is usually the governing criteria in curtain wall design. The specific weight (also known as the unit weight) is the Weight per unit Volume of a material or \gamma = \rho \ g Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere.
Thermal criteria
Relative to other building components, aluminum has a high heat transfer coefficient, meaning that aluminum is a very good conductor of heat. Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter from a region of higher Temperature to a region of lower This translates into high heat loss through aluminum curtain wall mullions. There are several ways to compensate for this heat loss, the most common way being the addition of thermal breaks. Thermal breaks are barriers between exterior metal and interior metal, usually made of polyvinyl chloride (PVC). An element of low thermal conductivity placed in an assembly to reduce or prevent the flow of thermal energy between conductive materials These breaks provide a significant decrease in the thermal conductivity of the curtain wall. However, since the thermal break interrupts the aluminum mullion, the overall moment of inertia of the mullion is reduced and must be accounted for in the structural analysis of the system.
Thermal conductivity of the curtain wall system is important because of heat loss through the wall, which affects the heating and cooling costs of the building. On a poorly performing curtain wall, condensation may form on the interior of the mullions. Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase This could cause damage to adjacent interior trim and walls.
Rigid insulation is provided in spandrel areas to provide a higher R-value at these locations. The term thermal insulation can refer to materials used to reduce the rate of Heat transfer, or the methods and processes used to reduce heat transfer A spandrel (less often spandril or splaundrel) is the space between two Arches or between an arch and a rectangular enclosure
Infills
Infill refers to the large panels that are inserted into the curtain wall between mullions. Infills are typically glass but may be made up of nearly any exterior building element.
Regardless of the material, infills are typically referred to as glazing, and the installer of the infill is referred to as a glazier. A Glazier is a Construction professional that selects cuts installs replaces and removes Residential, commercial, and Artistic Glass
Glass
By far the most common glazing type, glass can be of an almost infinite combination of color, thickness, and opacity. Float glass is a sheet of Glass made by floating molten glass on a bed of molten Tin. Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation especially visible Light. For commercial construction, the two most common thicknesses are 1/4 inch (6 mm) monolithic and 1 inch (25 mm) insulating glass. Insulated Glazing Unit or Insulating Glass Unit (commonly referred to as IGU) is a set of two or more sheets of glass spaced apart and Hermetically sealed Presently, 1/4 inch glass is typically used only in spandrel areas, while insulating glass is used for the rest of the building (sometimes spandrel glass is specified as insulating glass as well). A spandrel (less often spandril or splaundrel) is the space between two Arches or between an arch and a rectangular enclosure The 1 inch insulation glass is typically made up of two 1/4-inch lites of glass with a 1/2 inch (12 mm) airspace. The air inside is usually atmospheric air, but some inert gases, such as argon, may be used to offer better thermal transmittance values. "Inert gases" is also used in a narrower sense for Noble gases An inert gas is any Gas that is not reactive with elements Thermal transmittance, also known as U-value, is the rate of transfer of heat (in Watts through one square Metre of a structure divided by the difference In residential construction, thicknesses commonly used are 1/8 inch (3 mm) monolithic and 5/8 inch (16 mm) insulating glass. Larger thicknesses are typically employed for buildings or areas with higher thermal, relative humidity, or sound transmission requirements, such as laboratory areas or recording studios. Relative humidity is a measurement of the amount of Water vapor that exists in a gaseous mixture of air and water Acoustic transmission in building design refers to a number of processes by which sound can be transferred from one part of a building to another A recording studio is a facility for sound recording. Ideally the space is specially designed by an acoustician to achieve the desired acoustic properties (sound
Glass may be used which is transparent, translucent, or opaque, or in varying degrees thereof. In Optics, transparency (also called pellucidity) is the Material property of allowing In Optics, transparency (also called pellucidity) is the Material property of allowing Transparent glass usually refers to vision glass in a curtain wall. Spandrel or vision glass may also contain translucent glass, which could be for security or aesthetic purposes. Opaque glass is used in areas to hide a column or spandrel beam or shear wall behind the curtain wall. Another method of hiding spandrel areas is through shadow box construction (providing a dark enclosed space behind the transparent or translucent glass). Shadow box construction creates a perception of depth behind the glass that is sometimes desired.
Stone veneer
Thin blocks (3 to 4 inches (75-100 mm)) of stone can be inset within a curtain wall system to provide architectural flavor. The type of stone used is limited only by the strength of the stone and the ability to manufacture it in the proper shape and size. Common stone types used are: Arriscraft(calcium silicate);granite; marble; travertine; and limestone. Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Marble is a nonfoliated Metamorphic rock resulting from the Metamorphism of Limestone, composed mostly of Calcite (a crystalline form of Travertine is a Sedimentary rock. It is a natural chemical precipitate of Carbonate minerals; typically Aragonite, but often recrystallized to Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 The stone may come in several different finishes, which adds many more options for architects and building owners.
Panels
Metal panels can take various forms including aluminum plate; thin composite panels consisting of two thin aluminum sheets sandwiching a thin plastic interlayer; and panels consisting of metal sheets bonded to rigid insulation, with or without an inner metal sheet to create a sandwich panel. Other opaque panel materials include FRP (fiber-reinforced plastic) and stainless steel.
Louvers
A louver is provided in an area where mechanical equipment located inside the building requires ventilation or fresh air to operate. For the French museum see the Louvre A louver (American English or louvre (British English from the French l'ouvert They can also serve as a means of allowing outside air to filter into the building to take advantage of favorable climatic conditions and minimize the usage of energy-consuming HVAC systems. HVAC (pronounced either "H-V-A-C" or occasionally " H-vak " is an Initialism or Acronym that stands for " Heating Curtain wall systems can be adapted to accept most types of louver systems to maintain the same architectural sightlines and style while providing the necessary functionality.
Windows and vents
Most curtain wall glazing is fixed, meaning there is no access to the exterior of the building except through doors. However, windows or vents can be glazed into the curtain wall system as well, to provide required ventilation or operable windows. Nearly any window type can be made to fit into a curtain wall system.
Fire safety
Firestopping at the "perimeter slab edge", which is a gap between the floor and the backpan of the curtain wall is essential to slow the passage of fire and combustion gases between floors. A firestop is a Passive fire protection System of various components used to seal openings and joints in fire-resistance rated wall A building joint is a junction where Building elements meet without applying a static load from one element to another Spandrel areas must have non-combustible insulation at the interior face of the curtain wall. Some building codes require the mullion to be wrapped in heat-retarding insulation near the ceiling to prevent the mullions from melting and spreading the fire to the floor above. It is important to note that the firestop at the perimeter slab edge is considered a continuation of the fire-resistance rating of the floor slab. A fire-resistance rating typically means the duration for which a Passive fire protection System can withstand a standard fire resistance test. The curtain wall itself, however, is not ordinarily required to have a rating. This causes a quandary as Compartmentalization (fire protection) is typically based upon closed compartments to avoid fire and smoke migrations beyond each engaged compartment. In structures such as land-based Buildings traffic Tunnels Ships aerospace vehicles, or Submarines compartmentalization is the fundamental A curtain wall by its very nature prevents the completion of the compartment (or envelope). The use of fire sprinklers has been shown to mitigate this matter. As such, unless the building is sprinklered, fire may still travel up the curtain wall, if the glass on the exposed floor is shattered due to fire influence, causing flames to lick up the outside of the building. Falling glass can endanger pedestrians, firefighters and firehoses below. An example of this is the First Interstate Bank Fire in Los Angeles, California. Los Angeles (lɑˈsændʒələs los ˈaŋxeles in Spanish) is the largest City in the state of California and the American West California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The fire here leapfrogged up the tower by shattering the glass and then consuming the aluminium skeleton holding the glass. WikipediaNaming Aluminium's melting temperature is 660°C, whereas building fires can reach 1,100°C. The melting point of aluminium is typically reached within minutes of the start of a fire. Fire is the heat and light energy released during a Chemical reaction, in particular a combustion reaction. Firestops for such building joints can be qualified to UL 2079 -- Tests for Fire Resistance of Building Joint Systems. Sprinklering of each floor has a profoundly positive effect on the fire safety of buildings with curtain walls. A fire sprinkler system is an Active fire protection measure consisting of a water supply providing adequate pressure and flowrate to a water distribution piping system In the case of the aforementioned fire, it was specifically the activation of the newly installed sprinkler system, which halted the advance of the fire and allowed effective suppression. Had this not occurred, the tower would have collapsed onto fire crews and into an adjacent building, while on fire. Exceptionally sound cementitious spray fireproofing also helped to delay and ultimately to avoid the possible collapse of the building, due to having the structural steel skeleton of the building reach the critical temperature, as the post-mortem fire investigation report indicated. "Fireproof" redirects here For the album see Fireproof (album. Structural steel is Steel construction Material, a profile, formed with a specific Shape or cross section and certain standards of This fire proved the positive collective effect of both active fire protection (sprinklers) and passive fire protection (fireproofing). Active fire protection (AFP is an integral part of Fire protection. Passive fire protection (PFP is an integral component of the three components of structural Fire protection and fire safety in a Building.
Fireman knock-out glazing panels are often required for venting and emergency access from the exterior. Knock-out panels are generally fully tempered glass to allow full fracturing of the panel into small pieces and relatively safe removal from the opening. Architectural glass is glass that is used as a Building material.
Maintenance and repair
Curtain walls and perimeter sealants require maintenance to maximize service life. Perimeter sealants, properly designed and installed, have a typical service life of 10 to 15 years. Removal and replacement of perimeter sealants require meticulous surface preparation and proper detailing.
Aluminum frames are generally painted or anodized. Anodizing, or anodising, is an electrolytic Passivation process used to increase the thickness of the natural Oxide layer on the surface of metal Factory applied fluoropolymer thermoset coatings have good resistance to environmental degradation and require only periodic cleaning. Recoating with an air-dry fluoropolymer coating is possible but requires special surface preparation and is not as durable as the baked-on original coating.
Anodized aluminum frames cannot be "re-anodized" in place, but can be cleaned and protected by proprietary clear coatings to improve appearance and durability.
Exposed glazing seals and gaskets require inspection and maintenance to minimize water penetration, and to limit exposure of frame seals and insulating glass seals to wetting.
See also
References
External links
A mullion wall is a structural system in which the load of the floor slab is taken by prefabricated panels around theperimeterDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic