Q: What is a Curtain Wall?
A: Curtain wall is a term used to describe a building façade element,
generally assembled with aluminum and glass, which spans multiple floors, and
take into consideration design requirements such as: thermal expansion and
contraction; seismic motion; building sway and movement; water diversion; and
thermal efficiency for cost-effective heating, cooling, and lighting in a
building.
Q: What is a Window Wall?
A: Horizontal strips or ribbons consisting of an array of stacking windows
that create a horizontal band around or partially surrounding the building.
Q: What are Punched Windows?
A: Square or rectangular windows consisting of one or more pieces of glass
surrounded by window framing. Punched windows usually “dot” the building façade
unlike the ribbons of window wall. Punched windows can be quite large, and can
constitute a significant façade feature.
Q: What is Storefront?
A: Storefront is a general term applied to the framing material and doors
generally associated with the display windows of retail stores. Storefront
generally contains some form of glass and the framing can be manufactured from
several materials including: Aluminum, Steel, Wood, or can be all glass as
typified by the majority of Mall retail storefronts.
Q: What is Unitized construction vs. Stick construction?
A: The expressions Unitized and Stick refer to the method of construction
of a framing system for any glazed components within a building façade. Stick
construction generally refers to components that have been factory prepared,
shipped to the jobsite, and then erected piece by piece on-site. Unitized
construction conveys that the components have been factory prepared and
assembled then shipped to the jobsite as a completed unit. Each unit is then
connected together to form the façade. Stick construction takes less time in the
factory but takes longer to assemble on-site and presents some quality control
issues. Conversely, Unitized construction takes longer to manufacture in the
factory, however quality control can be strictly monitored, and it does
accelerate the erection of the façade on-site.
Q: How much will aluminum expand when heated?
A: A rough rule of thumb for the expansion of aluminum is ¼” for every
20’-0” of length. For an exact calculation, the formula is 0.0000128 x Length
(In) x Degrees of Temperature Rise (°F). Using this formula, a 20’-0” long piece
of aluminum will expand ¼” when the temperature rises 80°F from the temperature
that that piece of aluminum was first cut.
Q: What are the normal limits of deflection for glazed aluminum framing
systems?
A: Typically, the most common deflection limits specified for glazed
aluminum framing systems is L/175, where “L” is the length of the framing member
supporting the load. The American Architectural Manufacturers Association (AAMA)
provides an alternative, and more realistic deflection limit in their Technical
Interpretation Report (TIR) A11-04 - “Maximum Allowable Deflection of Framing
Systems for Building Cladding Components at Design Wind Loads”. This document
offers the following deflection limit criteria: Frames <= 13/-6” limit
deflection to L/175, Frames > 13’-6” limit deflection to L/240 + ¼”.
Q: What is Live Load deflection?
A: Live Loads are loads produced by use and occupancy of the building or
other structure and do not include construction or environmental loads such as
wind load, snow load, ice load, rain load, seismic load, or dead load. An
example of a Live Load is when a parade is passing a building and all the
occupants move to the window to watch. The floor slab will move down (deflect)
under the weight of all the people. After the parade has passed, and the
occupants return to their normal locations, the floor slab will return (move up)
to its normal position after the Live Load (the concentrated weight of the
people) has been removed.
Q: What is Design Pressure?
A: The Design Pressure (DP) is the pressure (measured in Pounds per Square
Foot [PSF]) that a building or building component should be designed to
accommodate without failure. Specifications for glazing systems will generally
indicate the DP in one of three manners: 1) Offer a specific DP (flat walls,
parapets and building corners will each generally have a different DP), 2) Refer
to a governing Building Code for standard methods of determining the DP, or 3)
Refer to a Wind Load Study performed on a scale model of the structure, that
yields the DP for various locations on the structure.
Q: How to convert Design Pressure to Miles Per Hour (MPH) ?
A: MPH = v PSF/0.00256
Q: How to convert Design Pressure to Inches of Water (In H2O) ?
A: H2O = PSF/5.2
Q: What is Dry Glazing?
A: Also called compression glazing, a term used to describe various means
of sealing monolithic and insulating glass in the supporting framing system with
synthetic rubber and other elastomeric gasket materials.
Q: What is a Kilowatt-hour?
A: The kilowatt-hour (symbolized kWh) is a unit of energy equivalent to
one kilowatt (1 kW) of power expended for one hour (1 h) of time. A typical home
will use 30 kWh of electrical energy in a day.
Q: What is Condensation?
A: The appearance of moisture (water vapor) on the surface of an object
caused by warm moist air coming into contact with a colder object.
Q: What is Dew Point?
A: The critical temperature at which vapor condenses from the atmosphere
and forms water.
Q: What is Double Glazing?
A: In general, any use of two lites of glass, separated by an air space,
within an opening, to improve insulation against heat transfer and/or sound
transmission. In insulating glass units the air between the glass sheets is
thoroughly dried and the space is sealed, eliminating possible condensation and
providing superior insulating properties.
Q: What is Edge Clearance?
A: Nominal spacing between the edge of the glass product and the bottom or
side of the glazing pocket (channel) of the framing system.
Q: What are Elastomeric products?
A: Products of or pertaining to any of the numerous flexible membranes,
sealants or gaskets that contain rubber or plastic.
Q: What is Emissivity?
A: The measure of a surface’s ability to emit long-wave infrared
radiation. The Low E (Low Emissivity) coatings of many modern insulated glass
units (IGU) are designed to control the amount of long-wave infrared radiation
(heat) passing through the IGU.
Q: What does EPDM stand for?
A: EPDM rubber (ethylene propylene diene monomer rubber) is an elastomer
which is characterized by wide range of applications. EPDM rubber is used in
automotive weather-stripping and seals, glass-run channel, radiator, garden and
appliance hose, tubing, washers, belts, electrical insulation, roofing membrane,
geomembranes, rubber mechanical goods, plastic impact modification,
thermoplastic, vulcanizates, motor oil additive, pond liner, electrical
cable-jointing and chainmaille applications.