BNP Mediais a Registered · oCalculation of total heat flow as a function of heat energy per time,...
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Transcript of BNP Mediais a Registered · oCalculation of total heat flow as a function of heat energy per time,...
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 of
handling, 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 Performanceo Keep heat out in summero Keep heat in in wintero Increased glazing area for daylighting opportunities
• Improve Securityo 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 Reflectiveo Low-eo Dynamic
Common Glass Types Used
Glass surfaces always start with #1 on exterior surface progressing higher toward interior surface
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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 Lite¼ in. (6 mm) Clear Annealed Inboard Lite
½ in. (12 mm) Spacer & Sealant System
Surfaces
Glass Surface Description
• Purpose of a Spacero Acts as structural member to maintain airspace
between glazing liteso Acts as carrier for desiccant systemo 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
• Desiccanto 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 anothero Convection: heat transfer due to the
movement of fluid between surfaceso Natural – hot air rises, cold air
sinkso Forced – wind, fans, etc.
o Radiation: heat energy travels through space and is reflected, absorbed or transmitted by materialso 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 radiationo 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 = 0.86o 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 = 0.90o 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.
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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 masso Space between glazing liteso 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 SizeRule of thumb – double spacebetween glazing lites = 3 dBreduction in sound transmission. Works when comparing STC butnot 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 Magazinewww.glassmagazine.com
American Architectural Manufacturers Association www.aamanet.org
ASTM Internationalwww.astm.org
Insulating Glass Manufacturers Alliancewww.igmaonline.org
USGlass Magazinewww.usglassmag.com
Industry Resources
COMFENInternational Glazing Database (IGDB)OpticsRESFENTHERMWINDOWwww.windows.lbl.gov/software/software.html
Blast Resistant Glazing Design for Architectural ApplicationsWindow 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 ArchitectsContinuing Education Systems Course
Critical Reasons to Specify Insulating Glass
1945 Old Gallows Rd Ste 750Vienna, VA 22182
703.442.4890
www.glass.org
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