Thermal Bridging and Whole Building Energy Performance

Transcription

1 Thermal Bridging and Whole Building Energy Performance Steve Murray, P.Eng. PMP Morrison Hershfield May 8 & 9,

2 Acknowledgments The real work for ASHRAE 1365 RP was done by others in MH s Vancouver Office including: Patrick Roppel Neil Norris Bennie Low 2

3 Presentation Outline How do we deal with thermal bridging? ASHRAE Research Project1365-RP The Conceptual Leap How can we use this now? 5 How might we use this in the future? 3

4 1 1How do we deal with thermal bridging? 4

5 Thermal Bridging What is a Thermal Bridge? Highly conductive material that by-passes insulation layer Areas of high heat transfer Can greatly affect the thermal performance of assemblies 5

6 Perspective How does heat flow through an enclosure assembly? vs. How to comply with energy standards like ASHRAE

7 ASHRAE Standard 90.1 ASHRAE Standard

8 ASHRAE Standard 90.1 ASHRAE 90.1 & thermal bridging TABLE A3.3 Assembly U-Factors for Steel-Frame Walls Overall U-Factor for Assembly of Base Wall Plus Continuous Insulation (Uninterrupted by Framing) Rated R-Value of Continuous Insulation = R-8 = R-8 + R-8 8

9 Thermal Bridging How is Thermal Bridging Typically Evaluated? Computer Modeling Hand Calculations Lab Measurement 9

10 We Live in a 3D World! 10

11 2 The ASHRAE 1365 Research Project 11

12 ASHRAE Research Project Goals and Objectives of the Project Calculate thermal performance data for common building envelope details for mid- and high-rise construction Develop procedures and a catalogue that will allow designers quick and straightforward access to information Provide information to answer the fundamental questions of how overall geometry and materials affect the overall thermal performance 12

13 ASHRAE Research Project Calibrated 3D Modeling Software Heat transfer software by Siemens PLM Software, FEMAP & Nx Model and techniques calibrated and validated against measured and analytical solutions ISO Standards for glazing Guarded hot box test measurements, 29 in total 13

14 ASHRAE Research Project Details Catalogue 40 building assemblies and details common to North American construction Focus on opaque assemblies, but also includes some glazing transitions Details not already addressed in ASHRAE publications Highest priority on details with thermal bridges in 3D 14

15 What is ASHRAE Research Project 1365-RP? 15

16 3 2 The Conceptual Leap 16

17 Overall Heat Loss Thermal Bridging and the Area Weighted Average L2,par apet Lro of 17

18 Overall Heat Loss Q Q o Q slab Additional heat loss due to the slab 18

19 Overall Heat Loss Ψ =Qslab/ L The linear transmittance represents the additional heat flow because of the slab, but with area set to zero 19

20 Overall Heat Loss Clear Field or o U o Q Types of Transmittances Linear Ψ Point χ 20

21 Overall Heat Loss Total Heat loss Q = heat loss due to clear field ( Ψ L) + Σ( n) = ( U A ) + Σ χ o Total + Heat loss due to anomalies 21

22 Overall Heat Loss U = A Total or Q ( Ψ L) + Σ ( χ n) Σ U = + A Total U The assembly U-factor is the clear field U-factor, plus all the linear and point transmittances o 22

23 Providing Results ASHRAE Data Sheets 23

24 Providing Results ASHRAE Data Sheets 24

25 Providing Results ASHRAE Data Sheets 25

26 Living Building Challenge 26

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28 Providing Results T i = T T surface inside T T outside outside ASHRAE Data Sheets T = T( T T ) + T surface i inside outside outside 28

29 4 3 How can we use this? 29

30 Evaluating Cladding Attachments Comparing to ASHRAE Requirements Vertical Z-Girts Horizontal Z-Girts Mixed Z-Girts Intermittent Z-Girts 30

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33 Ext. Insulated Steel Stud, Punch Window w/ Full Metal Window Flashing Ψ BTU/ft hr o F (0.454 W/m K) Flashing extents past thermal break to frame 33

34 Heat Flow through 4 x 8 Window Q = 32 x 0.35 = 11.2 BTU/ft hr o F Heat Flow through Window Transition Q = 24 x = 6.3 BTU/ft hr o F 34

35 Concrete Wall Punch Window w/ Interior Insulation Ψ = BTU/ft hr o F (0.048 W/m K) Flashing stops at thermal break 35

36 Heat Flow through 4 x 8 Window Q = 32 x 0.35 = 11.2 BTU/ft hr o F Heat Flow through Window Transition Q = 24 x = 0.67 BTU/ft hr o F 36

37 Continuous Insulation Systems IMP EIFS Continuous insulation systems can t escape the poor details problem 37

38 Insulated Metal Panels IMP Panel Example effectively continuous insulation but Potentially 40% (plus) heat flow attributed to window transition Panel assembly of U is only U (effective R-21 to R-8) when considering thermally inefficient details Improved to U (R-15) without much difficulty (no continuous metal flashing) 38

39 Insulated Metal Panels 39

40 Insulated Metal Panels 40

41 Direct heat flow path from interior to exterior through flashing and studs Potentially 40% (plus) heat flow attributed to window transition Improved to U (R-15) without much difficulty (no continuous metal flashing) 41

42 Glazing Spandrel Areas Curtain Wall Comparison No Spray Foam 42

43 Glazing Spandrel Areas Curtain Wall Comparison Spray Foam 43

44 Glazing Spandrel Areas Spandrel Section R Value Back Pan Insulation Detail 22 (Air in Stud Cavity) Detail 23 (Spray Foam in Stud Cavity) 44

45 Glazing Spandrel Areas No Spray Foam Spray Foam 45

46 Accounting for Details 46

47 Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ

48 Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ

49 Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ

50 Slab Edges - Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ

51 Accounting for Details 51

52 How to Use Data Sheets - Sample Project 52

53 How to Use Data Sheet Example 1 Steel stud with R-20 exterior insulation and horizontal girts and R-12 in the stud cavity; U Btu/hrft 2o F How to evaluate relative contribution of details? Wall Parameter Wall Width Wall Height Wall Parameter Values 30 ft (9.1m) 100 ft (30.5m) # of floors 10 Glazing % 40% Window Perimeter Length 28 ft (8.5m) # of Windows 25 Opaque Wall 1800 sqft (167.2m 2 ) 53

54 Linear Transmittance Corner Shelf angle Window Transition Parapet Slab 54

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57 Detail Summary Information Example 1 57

58 Calculations Sample Example 1 Total Heat loss Q ( Ψ L) + Σ( n) = ( U A ) + Σ χ o = heat loss due to clear field Total + Heat loss due to anomalies Q = Btu/hrft o 2o F * 30 ft (width) * 100ft (height) * %60 (area) = 88 Btu/hr o F ( Ψ L)slab = Btu/hrft 2o F * 30 ft (width) * 10 (# floors) = 134 Btu/hr o F 58

59 Heat Flow Summary Example 1 59

60 Opaque Wall Thermal Performance Summary Example 1 60

61 Contribution of Thermal Performance of Wall Assembly to Energy Use(GJ/m 2 of Floor Area) R-3.9 R-5.2 Clear Wall Only Including Poor Details Including Efficient Details R-4.5 R-10.2 R-5.0 R-14.3 R-5.3 R-16.7 Additional building energy use based on thermal performance of the building wall assembly for varying amounts of nominal exterior insulation for a mid-rise MURB in Edmonton (overall assembly thermal resistance in ft 2 ºF h/btu also given) 61

62 Case Study Cladding Retrofit & Whole Building Energy Case Study Cladding Retrofit & Whole Building Energy 62

63 Case Study Cladding Retrofit Cold Storage Existing Conditions 63

64 Case Study Cold Storage Existing Conditions 64

65 Case Study Cold Storage Existing Conditions Existing Conditions 65

66 Case Study Cold Storage Existing Conditions Attempted Joint Sealant Retrofits 66

67 Case Study Cold Storage Existing Conditions Existing Conditions - Concrete framed interior structure 67

68 Case Study Cold Storage Existing Conditions 68

69 Case Study Cold Storage Existing Conditions 69

70 Case Study Cold Storage Existing Conditions Interior view of walls -concrete at bottom - Exposed IMP above 70

71 Case Study Cold Storage Existing Conditions Interior view of walls -concrete at bottom - Exposed IMP above 71

72 Case Study Cold Storage Manufacturer Based Proposal Section at concrete frame to steel frame transition 72

73 Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 73

74 Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 74

75 Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 75

76 Case Study Cold Storage Manufacturer Based Proposal Isometric Section at typical steel frame wall at upper 6 storeys 76

77 Case Study Cold Storage MH Team Proposal First Off Salvage Existing wall panels in place Overcladwith new system Support Existing Panels with New Structure 77

78 Case Study Cold Storage MH Team Proposal Initial Concept Revised Thermally Broken Clips Not Adequate Structurally Replaced with Direct Bolted Angles and Stainless Bolts Delete C-channel 78

79 Case Study Cold Storage MH Team Proposal Here is close up of concept Exterior view 79

80 Case Study Cold Storage MH Team Proposal Challenge could be thermal bridging Here is close up of concept Interior view 80

81 Case Study Cold Storage MH Team Proposal Concrete wall areas not salvageable Fasteners failed Panels shifted Ice lensing suspected 81

82 Case Study Cold Storage MH Refined Design Concrete wall close up of concept Exterior view 82

83 Modeling Results Manufacturer Steel Stud No surprise Really bad 83

84 Modeling Results Manufacturer Steel Stud 84

85 Modeling Results Manufacturer Steel Stud 85

86 Modeling Results MH Team First iteration MH used a thermally broken clip system Second iteration Design was revised to use plain steel angle elements and stainless bolts Results were still very good 86

87 Modeling Results MH Team 87

88 Modeling Results MH Team 88

89 Modeling Results Comparison Comparing Results for Effective R- Values Manf r 89

90 Modeling Results Comparing Results for Estimated Energy Load Manf r 90

91 Modeling Results Comparing Results for Estimated Energy Load Includes roof areas whole building envelope energy Manf r 91

92 Key Point Whole Building Energy One can achieve same level of thermal performance using different approaches Efficient details, thin insulation Thick insulation, poor details At low effective R-values, increases = big energy savings To get increased effective R-values you need thermally efficient details and some insulation. 92

93 4 5 How might we use this in the future? 93

94 The Future It will likely become increasingly more difficult to ignore thermal bridging at intersections of assemblies Move beyond simply adding more insulation Better able to evaluate condensation resistance to improve building durability and occupant comfort 94

95 The Future of Energy Standards Different approaches can be employed in standards to fully account for thermal bridging using the same data Performance based Prescriptive based Solutions based The procedures and data provided by 1365-RP promises to enable more development and enforcement 95

96 Building Envelope Design Shift from nominal R-value thinking to effective R-value Move beyond simply adding more insulation. Examine cost effectiveness of insulating the building envelope through better details Look to building envelope to provide opportunity to achieve energy gains Be prepared to modify details and evaluate new products 96

97 Cladding Exterior Insulated Thermally broken clip system Fiberglass spacers 97

98 Thermal Breaks Concrete-concrete Steel-Steel 98

99 Glazing Vacuum insulated glass Translucent Daylighting Wall Systems Aluminum clad vacuum insulated panels Improved thermal breaks at frames 99

100 Strategies to Reduce Energy Use Large Office Building Ottawa Total Energy per area (GJ/m2) Relative Percent (%) Average window to wall area ratio Overall window USI value Window shading coefficient Overall wall RSI value Overall roof RSI value Heating efficiency Efficiency of exhaust air heat recovery Average lighting density Cooling efficiency 100

101 Closing Remarks 1. There is an easy way to evaluate thermal bridging by harnessing the power of 3D modeling to analyze common detail and provide generalizable results 2. We can separate the clear field from major thermal bridges and categorize the thermal quality of details 3. A results become available for typical details we only need to model unique, high concern details 101

102 Closing Remarks 4. Some details have more impact than others 5. It may not matter how much insulation you add if most of the heat loss is through the details 6. We can provide more accuracy for sizing systems and whole building energy simulations 7. 3D modeling can assess condensation resistance for high RH occupancies, cold climates, and unique architectural features 102

103 Accessing Information ashrae1365research/pages/insights-publications.aspx 103

104 Thank You 104