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Chapter 17 Glass and Glazing. Glass Benefits of Using Glass  Allows entry of natural light  Provide “views” of exterior environment  Entry of sunlight.

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Presentation on theme: "Chapter 17 Glass and Glazing. Glass Benefits of Using Glass  Allows entry of natural light  Provide “views” of exterior environment  Entry of sunlight."— Presentation transcript:

1 Chapter 17 Glass and Glazing

2 Glass Benefits of Using Glass  Allows entry of natural light  Provide “views” of exterior environment  Entry of sunlight provides warmth Disadvantages and/or Design Considerations  Limits occupant’s privacy  Lower resistance to thermal transmission  heat in the summer &  Cold in the winter  Initial & operating costs

3 Glass History Material used for Centuries  Early Processes (10th Century)  Crown Glass Heated glass blown into sphere Reheated & spun on “punty”(rod) Sphere becomes a “disk” Cooled & cut into pieces  Cylinder glass Heated glass blown into sphere Swung like a pendulum Elongated into a cylinder Ends cut off, split lengthwise Reheated, opened, flattened into rectangular sheet Cut into pieces  Neither had high “optical” quality

4 Glass History (cont.) Plate Glass  Introduced in the 17th Century  Process  Molten glass cast into frames  Spread into sheets by rollers  Cooled  Each side ground / polished  Larger sheets of High optical quality  Costly (until process was mechanized)

5 Glass History (cont.) Drawn Glass  Replaced cylinder glass, early 20th century  Flat sheets of glass drawn directly from a molten glass container  Production Process  Continuous production line - highly mechanized Drawn glass Ground & Polished (plate) To finished sheets of glass

6 Glass History (cont.) Float Glass  Process invented in 1959 in England (produced in US, 1963)  Has become a worldwide standard  Largely replaced drawn & plate glass  Production Process (Glass “floated” across a bath of molten tin)

7 Ribbon of Float Glass Process Benefits Surfaces parallel High Optical Quality (Comparable to Plate) Brilliant Surface Finish Economical Virtually all flat glass produced

8 Terminology Glazing - “...installation of a transparent material (usually glass) into an opening”  I.E. “Glass & Glazing” Glazier  A glass installer Lites (lights)  Individual pieces of glass

9 Glass as a Material Major ingredient - Sand (silicon dioxide) Strength  Individual fibers stronger than steel, but less stiff  In larger sheets - microscopic imperfections inherent with manufacturing process significantly reduce its strength  Cracks propagate from these imperfections near the point of maximum tension  Types of Breakage  Thermal Stress Breaks  Mechanical Stress Breaks

10 Glass Thicknesses Range of Thicknesses  3/32” Single strength  1/8” Double strength  Up to 1”+ Thickness Required is Determined by:  Size of Glass Lites (span)  Maximum Design (Wind) Loading  Acceptable Breakage Rate (most always some breakage)

11 Wind Testing Common on tall Buildings - Purpose: Establish expected loads Mockup for a 24 Story Condo

12 Tempered Glass Ordinary Glass - Annealed  glass cooled slowly under controlled conditions to avoid internal stresses Tempered Glass  Annealed glass that is:  Reheated  Surfaces cooled rapidly, core cooled more slowly  Induces permanent compressive stresses in edges & faces and tensile stresses in the core  Result: 4 times as strong in bending More resistant to thermal stress & impact

13 Tempered Glass When Tempered Glass Breaks:  The sudden release of the internal stresses:  Produces small square edged particles (as opposed to sharp, jagged pieces) Strength & breakage characteristics make it well suited for:  Exterior Doors  Floor to Ceiling Sheets of Glass  All-Glass Doors, Glass walls (ex; handball courts), basketball backboards Disadvantages  More Costly  Process may cause noticeable distortions  Cutting & Drilling must be prior to tempering

14 Uses of Tempered Glass

15 Heat-Strengthened Glass Substitute for Tempered Glass  Lower Cost, but  Less of the desirable qualities of tempered  Lower strength  Less desirable breakage characteristics Process Similar, however  Lower induced stresses  Less strength (only twice annealed)  Breakage characteristics more similar to annealed

16 Laminated Glass Sandwiching  Transparent interlayer (PVB)  Between layers of glass (can be multiple layers)  Bonded under heat & pressure PVB - Polyvinyl Butyral  Soft interlayer  Can be clear, colored, and/or patterned  Improves resistance to sound transmission  Upon breakage - PVB holds pieces of glass together Uses?  Skylights (overhead glazing)  Reduce noise (hospitals, classrooms, etc.)  Security glass (typically has multiple layers) Glass PVB Layer

17 the Bellagio Hotel

18 Hurricane Resistant Glass Large Missile Impact Test Laminated and Tempered

19 Fire Rated Glass Required for:  Fire rated doors  Rated Window and wall assemblies Glass Types  Specially Tempered Glass (rated for 20 minutes)  Wired Glass (mesh of wire in glass, rated for 45min.)  most common, but  changes the appearance of the opening  Optical Quality Ceramics (20min. to 3hr)

20 Wire Glass

21 Spandrel Glass Interior face  Ceramic based paints w/ pigmented glass particles (frits) applied  Heated / Tempered to form a ceramic coating  Opaque Lite  Match or contrast other glass  Often tempered - resist thermal stresses behind light Purpose  Conceal structure behind glass / curtainwall

22 Spandrel Glass (view from the inside)

23 Spandrel Glass (view from the outside)

24 Spandrel Glass

25 Tinted & Reflective Glass Why tint or apply a reflective coating to glass?  Reduce glare from sunlight  Reduce solar heat gain  Architectural look - Aesthetics

26 Clear Float Glass Sunlight OutsideInside Reflected Sunlight Absorbed & Reradiated as Heat 85% +/- sunlight enters

27 Tinted Glass Sunlight Reflected 14% to 75% Reradiated Outside Inside Result: Lower Cooling Costs Less “sunlight” Glare for people Fading FF&E

28 Tinted Glass Process  Chemical elements added to the molten glass  Colors available  Grays, bronzes, blues, greens, golds, etc.

29 Clear (untinted) Glass

30 Lightly tinted glass

31

32 Tinted glass

33 Reflective Glass Thin films of metal or metal oxide placed on the surface of the glass Film purpose:  Reflect sunlight  Reduce solar heat gain  Changes Appearance  Colored Mirror effect Can be placed on either face,  However, often on the inside face Glass Reflective Film

34 Reflective Glass

35

36

37 Shading Coefficient “Ration of total solar heat gain through a particular glass compared to heat gain through double-strength clear glass.” Shading Coefficient = Heat gain of a Glass type Heat gain thru Clear (double-strength) Tinted glass range:.5 to.8 Reflective glass range.3 to.7

38 Visible Transmittance “Measures the transparency of glass to visible light (rather than solar heat gain) Ranges:  Clear Glass.9  Tinted & Reflective <.9

39 Glazing Luminous Efficacy (K e ) K e = Visible Transmittance Shading Coefficient High K e  High amount of solar heat blocked while  Considerable amount of sunlight allowed to enter  Green & blue glass Low K e  Similar amounts of solar heat & sunlight blocked  Darker interior (less light)  Bronze, gold, & grays

40 Glass & Thermal Transmission Single Pane Glass 1” Polystyrene “Well” Insulated Wall 1/5 of Glass Thermal Transmission 1/20 of Glass Disadvantage of Glass: Higher Initial & Operating Costs, Reduced Comfort

41 Insulating Glass Two or more sheets of glass separated by an air space  Double Glazing: Two (2) sheets  Triple Glazing:Three (3) sheets (somewhat uncommon) Primary purpose of additional sheets of glass  Improve insulating value - reduce thermal transmission  Two (2) sheets - cuts heat loss in half (1/3 for 3 sheets) Increases initial cost but:  Reduces operating costs  Increases comfort  Provides additional architectural options

42 Insulating Glass Glass Air Space Spacer Sealant Spacer (Spline) Separates the glass Often Metallic Air Space Dry Air or Inert Gas (such as Argon) Sealant “Seals” Unit Prevent air escape & moisture penetration Glass Clear, reflective and/or tinted

43 Insulated Glass (tinted)

44

45 Metal Spline

46 Low-Emissivity Glass Low-E Glass Improves thermal performance  Ultra-thin, transparent, metallic coating  Generally placed on:  T he #2 or #3 position in insulating glass or  The #4 position in laminated glass  Reflects selected wavelengths of light & heat radiation  Allows entry of most short-wave (sunlight)  Reflects most longer-wave infrared radiation from objects and humans inside the building  Result:  Reduced heating & cooling load, increased comfort inside 4321 Insulated Glass

47 Thermal Performance Data Obtained from PPG Glass Clear, insulated, alum. spacer, air filled Add Low-E Glass Add “special” spacer Add Argon 33% Improvement 6% Improvement 13% Improvement

48 Glass with Changing Properties Thermochromic glass (darker when warmed by the sun) Photochromic (darker when exposed to bright light) Electrochromic (changes transparency with electricity) Photovoltaic (generates electricity from sunlight)

49 Self-Cleaning Glass  Proprietary product w/ coating of titanium oxide  Catalyst allowing sunlight to turn organic dirty into carbon dioxide and water Plastic Glazing Sheet  Materials – acrylic & polycarbonate  More expensive, higher coefficients of thermal expansion

50 Glazing - Small Lights Design Considerations  Low stresses from wind loading  Low stresses from thermal expansion / contraction Glazier’s points & Putty Wood Stop Snap-in Glazing Beads & Synthetic Rubber Gaskets

51 Glazing - Large Lites Design Considerations  Greater spans, Larger wind loads  Greater stresses from thermal expansion / contraction  Minor Frame irregularities can induce stresses Design Objectives  Effectively support glass weight (w/o inducing abnormal stresses)  Support glass against wind pressure (both positive & negative)  Isolate glass from from the supporting frame & building structure  Allow for independent expansion/contraction (glass & supports)  Separate glass from support materials that could induce stress or cause abrasion

52 Glass Support & Isolation from Frame Setting Blocks Synthetic Rubber the bottom edge Often quarter pts. Centering Shims Synthetic Rubber Center Lite Isolate Lit from the Frame

53 Bite Support against Wind Pressure Bite Too little - pop out Too much - stress w/ glass deflection Supporting Mullion Support Glass Transmit loads to structure Mullion

54 Gaskets “Seals” the Glass (1st line of defense) “Isolates” glass (from abrasion) Allows for Thermal Expansion/Contraction Accommodates Structure/Support deflection

55 Anchorage of Glass to Mullion(s) ‘Dry’ Glazed Lite (using compression)

56 Mullions being anchored to the structure

57 Glass being installed Insulated Glass Gaskets

58 Retainer (compression) strips installed

59 Finished Installation (Snap on Covers applied over the retainer strips)

60 Lock-Strip Gasket

61 Structural Silicone Flush Glazing Mullions on the “inside” of the Glass Glass adhered by Silicone Sealant or Retainer

62 Structural Silicone Flush Glazing

63

64 Butt-Joint Glazing Head & Sill with conventional frames Vertical Mullions eliminated Vertical joints - caulked

65 Butt-Joint Glazing

66 Truss-like Mullions with ‘architectural qualities’ to support wind loading on a tall entrance

67 Weeps / “Drainage” System

68 Sampling of Mullion Colors Aluminum & Glass L.C.

69 Suspended Glazing System Tempered & Laminated Glass Glass support & anchorage

70 Structural Glazing System (exterior)

71 Structural Glazing System (interior)

72 Glass Mullion System tempered glass

73 Glass & Design Methods to compensate for its poor thermal properties  Double & triple glazing  Low E coatings  Low conductivity gas fills  Tinting, reflective coatings  Curtains, shutters  Window sizing & orientation on the building  Shading or overhangs

74 Glass & the Building Codes Codes concerned with:  Structural Adequacy  wind & impact loads  Providing natural light in habitable rooms  may require a certain glass area as a % of floor area  Safety concerns with breakage  skylights, overhead glazing, in or near doors, “clear” sheets of glass that could be mistaken for an opening  Use of laminated, tempered, etc.  Prevention of fire  maximum glazed area, wire glass  Energy consumption  may require double glazing, storm windows, limit the maximum % of glazed area


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