Thermal Bridging and Whole Building Energy Performance Steve Murray, P.Eng. PMP Morrison Hershfield May 8 & 9, 2013 1
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
Presentation Outline 1 2 3 4 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
1 1How do we deal with thermal bridging? 4
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
Perspective How does heat flow through an enclosure assembly? vs. How to comply with energy standards like ASHRAE 90.1 6
ASHRAE Standard 90.1 ASHRAE Standard 90.1 7
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
Thermal Bridging How is Thermal Bridging Typically Evaluated? Computer Modeling Hand Calculations Lab Measurement 9
We Live in a 3D World! 10
2 The ASHRAE 1365 Research Project 11
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
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
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
What is ASHRAE Research Project 1365-RP? 15
3 2 The Conceptual Leap 16
Overall Heat Loss Thermal Bridging and the Area Weighted Average L2,par apet Lro of 17
Overall Heat Loss Q Q o Q slab Additional heat loss due to the slab 18
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
Overall Heat Loss Clear Field or o U o Q Types of Transmittances Linear Ψ Point χ 20
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
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
Providing Results ASHRAE Data Sheets 23
Providing Results ASHRAE Data Sheets 24
Providing Results ASHRAE Data Sheets 25
Living Building Challenge 26
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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
4 3 How can we use this? 29
Evaluating Cladding Attachments Comparing to ASHRAE 90.1-2007 Requirements Vertical Z-Girts Horizontal Z-Girts Mixed Z-Girts Intermittent Z-Girts 30
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Ext. Insulated Steel Stud, Punch Window w/ Full Metal Window Flashing Ψ 0.263 BTU/ft hr o F (0.454 W/m K) Flashing extents past thermal break to frame 33
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 0.263 = 6.3 BTU/ft hr o F 34
Concrete Wall Punch Window w/ Interior Insulation Ψ = 0.028 BTU/ft hr o F (0.048 W/m K) Flashing stops at thermal break 35
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 0.028 = 0.67 BTU/ft hr o F 36
Continuous Insulation Systems IMP EIFS Continuous insulation systems can t escape the poor details problem 37
Insulated Metal Panels IMP Panel Example effectively continuous insulation but Potentially 40% (plus) heat flow attributed to window transition Panel assembly of U-0.048 is only U-0.127 (effective R-21 to R-8) when considering thermally inefficient details Improved to U-0.065 (R-15) without much difficulty (no continuous metal flashing) 38
Insulated Metal Panels 39
Insulated Metal Panels 40
Direct heat flow path from interior to exterior through flashing and studs Potentially 40% (plus) heat flow attributed to window transition Improved to U-0.065 (R-15) without much difficulty (no continuous metal flashing) 41
Glazing Spandrel Areas Curtain Wall Comparison No Spray Foam 42
Glazing Spandrel Areas Curtain Wall Comparison Spray Foam 43
Glazing Spandrel Areas Spandrel Section R Value 10 9 8 7 6 5 4 3 2 1 0 7.4 8.2 4.2 8.8 9.1 4.8 5.0 3.4 0 5 10 15 20 25 30 Back Pan Insulation Detail 22 (Air in Stud Cavity) Detail 23 (Spray Foam in Stud Cavity) 44
Glazing Spandrel Areas No Spray Foam Spray Foam 45
Accounting for Details 46
Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ 0.59 0.34 47
Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ 0.21 0.12 48
Slab Edges Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ 0.47 0.27 49
Slab Edges - Brick Veneer SI (W/m K) IP (BTU/hr ft o F) Ψ 0.31 0.18 50
Accounting for Details 51
How to Use Data Sheets - Sample Project 52
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-0.049 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
Linear Transmittance Corner Shelf angle Window Transition Parapet Slab 54
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Detail Summary Information Example 1 57
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 = 0.049 Btu/hrft o 2o F * 30 ft (width) * 100ft (height) * %60 (area) = 88 Btu/hr o F ( Ψ L)slab = 0.445 Btu/hrft 2o F * 30 ft (width) * 10 (# floors) = 134 Btu/hr o F 58
Heat Flow Summary Example 1 59
Opaque Wall Thermal Performance Summary Example 1 60
Contribution of Thermal Performance of Wall Assembly to Energy Use(GJ/m 2 of Floor Area) 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 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
Case Study Cladding Retrofit & Whole Building Energy Case Study Cladding Retrofit & Whole Building Energy 62
Case Study Cladding Retrofit Cold Storage Existing Conditions 63
Case Study Cold Storage Existing Conditions 64
Case Study Cold Storage Existing Conditions Existing Conditions 65
Case Study Cold Storage Existing Conditions Attempted Joint Sealant Retrofits 66
Case Study Cold Storage Existing Conditions Existing Conditions - Concrete framed interior structure 67
Case Study Cold Storage Existing Conditions 68
Case Study Cold Storage Existing Conditions 69
Case Study Cold Storage Existing Conditions Interior view of walls -concrete at bottom - Exposed IMP above 70
Case Study Cold Storage Existing Conditions Interior view of walls -concrete at bottom - Exposed IMP above 71
Case Study Cold Storage Manufacturer Based Proposal Section at concrete frame to steel frame transition 72
Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 73
Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 74
Case Study Cold Storage Manufacturer Based Proposal Section at typical steel frame wall at upper 6 storeys 75
Case Study Cold Storage Manufacturer Based Proposal Isometric Section at typical steel frame wall at upper 6 storeys 76
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
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
Case Study Cold Storage MH Team Proposal Here is close up of concept Exterior view 79
Case Study Cold Storage MH Team Proposal Challenge could be thermal bridging Here is close up of concept Interior view 80
Case Study Cold Storage MH Team Proposal Concrete wall areas not salvageable Fasteners failed Panels shifted Ice lensing suspected 81
Case Study Cold Storage MH Refined Design Concrete wall close up of concept Exterior view 82
Modeling Results Manufacturer Steel Stud No surprise Really bad 83
Modeling Results Manufacturer Steel Stud 84
Modeling Results Manufacturer Steel Stud 85
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
Modeling Results MH Team 87
Modeling Results MH Team 88
Modeling Results Comparison Comparing Results for Effective R- Values Manf r 89
Modeling Results Comparing Results for Estimated Energy Load Manf r 90
Modeling Results Comparing Results for Estimated Energy Load Includes roof areas whole building envelope energy Manf r 91
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
4 5 How might we use this in the future? 93
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
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
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
Cladding Exterior Insulated Thermally broken clip system Fiberglass spacers 97
Thermal Breaks Concrete-concrete Steel-Steel 98
Glazing Vacuum insulated glass Translucent Daylighting Wall Systems Aluminum clad vacuum insulated panels Improved thermal breaks at frames 99
Strategies to Reduce Energy Use Large Office Building Ottawa Total Energy per area (GJ/m2) 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5-100 -90-80 -70-60 -50-40 -30-20 -10 0 10 20 30 40 50 60 70 80 90 100 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
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
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
Accessing Information 103 http://www.morrisonhershfield.com/ ashrae1365research/pages/insights-publications.aspx 103
Thank You smurray@morrisonhershfield.com 104