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BNP Media is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or product._____________________________________
Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
• List the primary components of an insulating
glass unit construction or assembly
• Describe the purpose of a spacer in an
insulating glass unit assembly
• Discuss how insulating glass units provide
enhanced levels of security and safety
performance
• State two ways the acoustical performance of an
insulating glass unit can be improved
Learning Objectives
The demand for energy savings, building
occupancy safety and comfort have enabled the
glass and glazing industry to bring many
innovations to market. This course will cover the
basic components of insulating glass and review
some of the key performance attributes they
provide.
Course Description
• Improve Thermal Performance
o Keep heat out in summer
o Keep heat in in winter
o Increased glazing area for daylighting opportunities
• Improve Security
o Some resistance to blast, ballistics, burglars and
hurricanes
• Improve Acoustical Performance
o Reduce noise inside buildings from exterior sources
• Specialty Features and Aesthetics
o Varying colors, internal blinds, dynamic glazing
* Performance varies based on glazing configuration.
Consult the fabricator to achieve desired performance.
Why Specify Insulating Glass?
Definition: (ASTM E2190)
Insulating Glass: “n—a preassembled unit, comprising lites of glass, which are sealed at the edges and separated by dehydrated space(s), intended for vision areas of buildings. The unit is normally used for windows, window walls, picture windows, sliding doors, patio doors, or other types of fenestration.”
Definition: (web)
Insulating Glass: “n—Two or more lights of glass spaced apart and hermetically sealed to form a single-glazed unit with an air space between each light.”
Insulating Glass: Defined
Glazing Types
Insulating Glazing Components
• Double Glazing:
two glazing lites, one desiccated (dehydrated) space
• Triple Glazing:
three glazing lites, two desiccated spaces
Common IG Unit Configurations
Source: http://www.sinoruntai.com/insulated.html
• Can have 4+ glazing layers and multiple desiccated spaces but not common
• Any multiple spacer gap construction can utilize suspended films in place of internal glass lites
Photo Credit: Northerm, Eastman Chemical Company
Other IG Unit Configurations
• Glazing lites are held apart by spacer “system” that
includes spacer, desiccant and sealants
• Spacer system serves five principle functions:
o Maintain space between glazing lites (spacer)
o Dry gas in space to prevent moisture
condensation (desiccant)
o Prevent moisture from penetrating space (spacer
& sealants)
o Retain gas fills within space (spacer & sealants)
o Maintain hermetic seal about IG perimeter
(spacer & sealants)
IGU Construction
• Annealed
• Tempered
• Heat-Strengthened
• Laminated
• Tinted/Colored
• Coated
o Reflective
o Low-e
o Dynamic
Common Glass Types Used
Glass surfaces always start with #1 on exterior surface
progressing higher toward interior surface
11 22 33 44
¼ in. (6 mm) Green Heat-Strengthened
Outboard Lite
¼ in. (6 mm) Green Heat-Strengthened
Outboard Lite
¼ in. (6 mm) Clear Annealed
Inboard Lite
¼ in. (6 mm) Clear Annealed
Inboard Lite
½ in. (12 mm) Spacer & Sealant System
Surfaces
Glass Surface Description
• Purpose of a Spacer
o Acts as structural member to maintain airspace between glazing lites
o Acts as carrier for desiccant system
o Acts as support system for sealants
Spacer System Components
• Spacer types include:
o Rigid: metal, plastic or combination that are extruded, roll formed or assembled to create rigid spacer. Are typically filled with desiccant.
o Flexible: thermoset or thermoplastic rubbers and plastics with rigid internal components to maintain glazing space. Typically have desiccant integral to spacer.
Spacer System Components
• Two principle spacer/sealant systems:o Single Seal – primary sealant acts as moisture vapor
barrier, gas retention barrier and provides structural
integrity
o Dual Seal – primary sealant acts as moisture vapor
barrier and gas retention barrier while secondary
sealant provides structural integrity (may also
supplement primary sealant)
o Note: Both rely on ability of spacer component to resist
moisture and/or gas transfer
Type of Spacer/Sealant Systems
• Primary: acts principally to prevent
moisture and gas transfer across edge
seal. Not typically a structural sealant but
have very low moisture vapor and gas
transmission rates.
o Examples: Polyisobutylene (PIB),
reactive hot melt (RHM)/dual-seal
equivalent (DSE), hot melt butyl
• Secondary: acts principally to maintain integrity of IGU. Not typically a good moisture vapor or gas transmission sealant.
o Examples: Polyurethane (PU), Polysulfide (PS), Silicone (Si).
Insulating Glass Components Sealants
• Desiccant
o Beads, powder or matrix that is retained by spacer and adsorbs moisture from inside the IG unit to prevent internal condensation
o Some desiccants may also adsorb volatiles from inside the IG unit
Spacer System Components
• Three modes of heat flow through IG:o Conduction: heat transfer through a
material from one surface to another
o Convection: heat transfer due to the movement of fluid between surfaces
o Natural – hot air rises, cold air sinks
o Forced – wind, fans, etc.
o Radiation: heat energy travels through space and is reflected, absorbed or transmitted by materials
o Short wave – higher energy heat primarily from source (sun)
o Long wave – heat energy that is re-radiated from surfaces
• Heat always flows from high concentration (where it’s hot) to low concentration (where it’s not).
Purpose #1: Improve Thermal
Performance
• Single lite of glass (monolithic) with no coating (clear) has minimal resistance to conductive and radiant heat flow
• Adding second lite and airspace reduces conductive heat flow by more than ½!
• Low Emissivity (Low E) coatings on one or more glazing surfaces can reduce heat flow due to radiation an additional 50%
• Further benefits available by adding insulating gases (argon, krypton) in spacer gap and warm edge spacer systems
Purpose #1: Improve Thermal
Performance
Thermal Transmittance (U-Factor)
Measure of air-to-air heat transmission (loss or gain) due to difference in indoor and outdoor temperatures and incident radiation.
o Combination of conduction, convection and radiation
o Calculation of total heat flow as a function of heat energy per time, per exposed area per degree of temperature difference
•Example: BTU/hr-ft²-°F
o As the U-factor decreases, so does the amount of heat that is transmitted through the glazing system.
o A lower U-factor reduces the amount of heat transferred through the fenestration product.
Performance Characteristics
Solar Heat Gain Coefficient (SHGC)
Ratio of the solar heat gain entering the space area through the fenestration product to the incident solar radiation. Solar heat gain includes directly transmitted solar heat and absorbed solar radiation, which is then reradiated, conducted or convected into the interior.
Performance Characteristics
Solar Heat Gain Coefficient (SHGC)
Dimensionless value representing the percentage of incident solar radiation transmitted to the interior
• Ranges from 0 (no infrared transmission) to 1 (no infrared resistance)
• Examples:
o Clear single glazing
SHGC = 0.86
o Double glazed, low solar
gain low-e SHGC = 0.39
Performance Characteristics
Visible Light Transmittance (VLT)
The percentage of visible light within the solar spectrum (390 to 780 nanometers) that is transmitted through the center of glass of an IG unit. Does not include effects due to edge of glass or framing
• Not a measure of heat energy transfer but is directly affected by means to control heat flow such as tints, reflective coatings and low emissivity (low-e) coatings
• Measured as a percentage of transmitted available light
• Examples:
o Clear single glazing VLT = 0.90
o Double glazed bronze tint VLT = 0.62
Performance Characteristics
Source: twinqu.com
Visible Light Transmittance
Dynamic Light and Solar Heat Gain Control
A dynamic glazing product has the fully reversible ability to change its optical performance properties, such as visible light and near infrared transmission and solar heat gain coefficient.
• Electrochromic
• Photochromic
• Thermochromic
Performance Characteristics
courtesy of Sage Glass
Dynamic Glazing
Condensation Resistance
Measure of the ability of a material/system to resist moisture condensation on interior surfaces
• Typically a localized event taking place on the coldest areas of the systems
• Function of convection, conduction, air leakage and indoor relative humidity. “Cold spots” occur typically along the lower horizontal surfaces where moisture or frost form
• Calculated value as either “Condensation Resistance Factor (CRF)” under AAMA or “Condensation Resistance” rating under the NFRC
Performance Characteristics
Interior Condensation on IGU
• Multi-layer, laminated IG systems used for protection
against hurricane, blast and ballistic impact.
• Can also improve protection against forced entry.
11 22 3 4 5 6
½ in. (12 mm) Spacer & Sealant System½ in. (12 mm) Spacer & Sealant System
5/16 in. (8 mm) Clear Laminated Inboard Lite
1/8 in. (3 mm) Clear Annealed Outer Lite –
0.060 in. (1.52 mm) Interlayer – 1/8 in. (3
mm) Clear Annealed Inner Lite
5/16 in. (8 mm) Clear Laminated Inboard Lite
1/8 in. (3 mm) Clear Annealed Outer Lite –
0.060 in. (1.52 mm) Interlayer – 1/8 in. (3
mm) Clear Annealed Inner Lite
¼ in. (6 mm) Green Heat-Strengthened
Outboard Lite with Low-emissivity Coating #2
Surface
¼ in. (6 mm) Green Heat-Strengthened
Outboard Lite with Low-emissivity Coating #2
Surface
Surfaces
Purpose #2: Improved Safety
and Security
Impacted Window
Impacted Window
• Sound is transmitted through glazing systems at various frequencies due to vibration of components.
• Dampening of acoustical energy reduces sound transmission through glazing.
• Primary factors are:
o Glazing mass
o Space between glazing lites
o Type of glazing and spacer system
Purpose #3: Improved Acoustical
Performance
Sound Transmission Class (STC)
A single number rating derived from individual transmission losses at specified test frequencies. It is used for interior walls, ceilings and floors and in the past was also used for preliminary comparison of the performance of various glazing materials.
Outside-Inside Transmission Class (OITC)
A rating used to classify the performance of glazing in exterior applications.
Rating Systems
Glazing Mass
“Mass Law” states a 6 dB reduction in sound transmission for every doubling of unit mass per area. Therefore, thicker glass reduces sound transmission but…also makes for very heavy units!
Glazing Space Size
Rule of thumb – double space
between glazing lites = 3 dB
reduction in sound transmission.
Works when comparing STC but
not so well with OITC.
Purpose #3: Improved Acoustical
Performance
Glazing Type
The same glazing type (construction, thickness,
temper, etc.) will respond similarly to the same
frequencies; if one vibrates the other will too.
“Decoupling” of interior and exterior lites is
accomplished by utilizing different types and/or
thickness of glazing that don’t respond the same at the
same frequencies.
Purpose #3: Improved Acoustical
Performance
Glazing Type (continued)
Laminated glass dampens sound energy through most
of the frequency spectrum thereby reducing sound
transmission.
Also acts to decouple acoustic response from opposite
lite within IGU.
Purpose #3: Improved Acoustical
Performance
• Diffused Light Panels
• Grids/Blinds
• Colors
• Spandrel Panels
Purpose #4: Specialty Features and
Aesthetics
National Glass Association, with GANA
www.glass.org
• Glass Informational Bulletins
• Glazing Manual
• Laminated Glazing Reference Manual
• Specifiers Guide to Architectural Glass
Industry Resources
Glass Magazine
www.glassmagazine.com
American Architectural Manufacturers Association
www.aamanet.org
ASTM International
www.astm.org
Insulating Glass Manufacturers Alliance
www.igmaonline.org
USGlass Magazine
www.usglassmag.com
Industry Resources
COMFEN
International Glazing Database (IGDB)
Optics
RESFEN
THERM
WINDOW
www.windows.lbl.gov/software/software.html
Blast Resistant Glazing Design for Architectural Applications
Window Glass Design (According to ASTM E1300)
Wind Loads on Structures (According to ASCE 7)
www.standardsdesign.com
Software Resources
• IGMA “Preventing IG Failures”
• “Residential Windows: A Guide to New Technologies
and Energy Performance” 2nd Edition – W.W. Norton
2000
• AAMA TIR-A1-04, “Sound Control for Fenestration
Products”
Sources
• List the primary components of an insulating
glass unit construction or assembly
• Describe the purpose of a spacer in an
insulating glass unit assembly
• Discuss how insulating glass units provide
enhanced levels of security and safety
performance
• State two ways the acoustical performance of an
insulating glass unit can be improved
Learning Objectives
This concludes The American Institute of Architects
Continuing Education Systems Course
Critical Reasons to Specify Insulating Glass
1945 Old Gallows Rd Ste 750
Vienna, VA 22182
703.442.4890
www.glass.org
Conclusion
