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Achieving Net Zero Energy at Conventional Cost

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The goal: a Net Zero Energy house at conventional cost. Here are 5 early-design studies we did to set the project on track, and 3 strategies we employed to get the design on-budget.

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Achieving Net Zero Energy at Conventional Cost

  1. 1. Copyright © 2017 Sterner Design, LLC IOWA NEST RESIDENCE Achieving Net Zero Energy At Conventional Cost Carl S. Sterner, Assoc. AIA, LEED AP Owner, Sterner Design LLC Director, Sol Design + Consulting 20 April 2017 Copyright © 2017 Sterner Design, LLC
  2. 2. Copyright © 2017 Sterner Design, LLC Topics 1.  How early analysis informed design ! 5 studies that set the design on track 2.  Monitoring ! how are we doing? 3.  Designing for a conventional budget ! 3 strategies / lessons learned 4.  Building science ! thermal + air + vapor barriers
  3. 3. Copyright © 2017 Sterner Design, LLC Project requirements •  ~2400 s.f. residence •  Net Zero Energy •  Underground / of the land •  Avoid conventional AC if possible •  Do all of this on a conventional budget
  4. 4. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC The site
  5. 5. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC
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  9. 9. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC
  10. 10. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC The design
  11. 11. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC
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  17. 17. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC ! FOLLOW OUR PROGRESS @ WWW.IOWANEST.COM
  18. 18. Copyright © 2017 Sterner Design, LLC Pre-design & Schematic Analysis 5 questions that informed design
  19. 19. Copyright © 2017 Sterner Design, LLC Can performance
 inspire design? The question behind them all:
  20. 20. Copyright © 2017 Sterner Design, LLC 1.
 What passive design strategies are most important?
  21. 21. Copyright © 2017 Sterner Design, LLC Sensitivity analysis
  22. 22. Copyright © 2017 Sterner Design, LLC + ! STEP-BY-STEP PROCESS @ WWW.IOWANEST.COM How was this done?
  23. 23. Copyright © 2017 Sterner Design, LLC Overlaying cost = “most bang for the buck”
  24. 24. Copyright © 2017 Sterner Design, LLC Building form?? Earth berming?? Space layout / thermal zoning?? Peak Loads! What I would do differently:
  25. 25. Copyright © 2017 Sterner Design, LLC A study I should’ve done: (Glazing ratio + bldg form with optimal shading)
  26. 26. Copyright © 2017 Sterner Design, LLC 2.
 Can we avoid mechanical cooling?
  27. 27. Copyright © 2017 Sterner Design, LLC 6 factors that effect human comfort
  28. 28. Copyright © 2017 Sterner Design, LLC Strategy: Earth Berming ! air temp + radiant temp
  29. 29. Copyright © 2017 Sterner Design, LLC Strategy: Thermal Mass ! air temp + radiant temp
  30. 30. Copyright © 2017 Sterner Design, LLC Strategy: Shading ! air temp + radiant temp
  31. 31. Copyright © 2017 Sterner Design, LLC Strategy: Natural Ventilation + Ceiling Fans ! air movement
  32. 32. Copyright © 2017 Sterner Design, LLC Comfort analysis (PMV) Design case without natural ventilation = uncomfortable
  33. 33. Copyright © 2017 Sterner Design, LLC Not possible to get into range without dehumidification … ! STEP-BY-STEP PROCESS @ WWW.IOWANEST.COM
  34. 34. Copyright © 2017 Sterner Design, LLC … but comfort is personal. Clients are willing to try for no A/C. ! STEP-BY-STEP PROCESS @ WWW.IOWANEST.COM
  35. 35. Copyright © 2017 Sterner Design, LLC Strategy: Plan for the Future ! add dehumidification / cooling
  36. 36. Copyright © 2017 Sterner Design, LLC How the analysis thus far
 informed the design …
  37. 37. Copyright © 2017 Sterner Design, LLC Construction: ICFs + exposed mass
  38. 38. Copyright © 2017 Sterner Design, LLC Performance Concept: Insulated mass + operable envelope
  39. 39. Copyright © 2017 Sterner Design, LLC Language: Planar vs Volumetric vs
  40. 40. Copyright © 2017 Sterner Design, LLC
  41. 41. Copyright © 2017 Sterner Design, LLC 3.
 Which design option is best?
 (And why?)
  42. 42. Copyright © 2017 Sterner Design, LLC OPTION 1: REVEAL OPTION 2: BEACON EUI EUI Concepts
  43. 43. Copyright © 2017 Sterner Design, LLC OPTION 3: GLASS PAVILIONS OPTION 4: TERRACE EUI EUI Concepts
  44. 44. Copyright © 2017 Sterner Design, LLC OPTION 5: ROLLING HILLS Daylight Legend Energy Legend EUI Concepts
  45. 45. Copyright © 2017 Sterner Design, LLC Concept Comparison
  46. 46. Copyright © 2017 Sterner Design, LLC Concept Comparison
  47. 47. Copyright © 2017 Sterner Design, LLC ! STEP-BY-STEP PROCESS @ WWW.IOWANEST.COM Concept Comparison
  48. 48. Copyright © 2017 Sterner Design, LLC Envelope area vs EUI Glazed area vs cooling Glazed area vs EUI Envelope area vs heating What’s driving energy performance? Copyright © 2017 Sterner Design, LLC
  49. 49. Copyright © 2017 Sterner Design, LLC Design response
  50. 50. Copyright © 2017 Sterner Design, LLC 4.
 What’s the best combination of strategies?
  51. 51. Copyright © 2017 Sterner Design, LLC
  52. 52. Copyright © 2017 Sterner Design, LLC ! STEP-BY-STEP PROCESS @ WWW.IOWANEST.COM
  53. 53. Copyright © 2017 Sterner Design, LLC Sefaira analysis was used to test m and discover the best path toward Response Curves were used to fur parameters, based on the latest ve the Sustainable Design Narrative fo The complete Sefaira analysis can apps.sefaira.com/concept/project/ single?id=30986&cid=94270&did=Copyright © 2017 Sterner Design, LLC
  54. 54. Copyright © 2017 Sterner Design, LLC NET ZERDRAFT SET - NOT FOR CONSTRUCTION NEST RESIDENCE // Fremont, IA TERNER DESIGN // 1555 Pullan Ave., Cincinnati, OH 45223 Copyright © 2015 Sterner Design. All rights reserved. What are the optimal envelope properties?
  55. 55. Copyright © 2017 Sterner Design, LLC We’ve come a long way … Energy Footprint (kBTU) Peak Space Heating Demand (ton) Energy Footprint (kBTU) Peak Space Heating Demand (ton) Code Baseline As Designed
  56. 56. Copyright © 2017 Sterner Design, LLC 5.
 Is the glass productive?
  57. 57. Copyright © 2017 Sterner Design, LLC Productive glass + productive mass Typical configuration = Portions of the glass are unproductive This design = 100% of the glass is “productive” as a passive solar collector
  58. 58. Copyright © 2017 Sterner Design, LLC (Recognize that angle??)
  59. 59. Copyright © 2017 Sterner Design, LLC Direct sunlight analysis for shading optimization
  60. 60. Copyright © 2017 Sterner Design, LLC Is there enough daylight? Copyright © 2017 Sterner Design, LLC
  61. 61. Copyright © 2017 Sterner Design, LLC PRE-DESIGN: Passive strategies • Net Zero Energy feasibility CONCEPT: Comparison • Correlation SCHEMATIC / DEVELOPMENT: Envelope optimization • Shading design (direct sunlight) • Daylighting refinements Summary of studies
  62. 62. Copyright © 2017 Sterner Design, LLC Monitoring The proof is in the data …
  63. 63. Copyright © 2017 Sterner Design, LLC Data to date (January – April 2017) ! LIVE DATA @ WWW.IOWANEST.COM/MONITOR
  64. 64. Copyright © 2017 Sterner Design, LLC ! LIVE DATA @ WWW.IOWANEST.COM/MONITOR Remarkable stability, even though some insulation + air sealing still remains (as of April)
  65. 65. Copyright © 2017 Sterner Design, LLC Designing for Budget 3 strategies (AKA hard lessons)
  66. 66. Copyright © 2017 Sterner Design, LLC Cost comparison vs conventional house in Iowa
  67. 67. Copyright © 2017 Sterner Design, LLC But if you remove the green roof & custom corner lift-slide …
  68. 68. Copyright © 2017 Sterner Design, LLC FINISHES ! DESIGN MECHANICAL SYSTEMS ! INTEGRATIVE DESIGN ENCLOSURE ! DESIGN + MATERIALS FOUNDATION ! DESIGN PLUMBING ! DESIGN Where did the savings come from?
  69. 69. Copyright © 2017 Sterner Design, LLC 1.
 Keep the form simple.
 
 (DESIGN)
  70. 70. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC The original schematic design
  71. 71. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC The original schematic design = 2X over budget
  72. 72. Copyright © 2017 Sterner Design, LLC What drove the cost?
  73. 73. Copyright © 2017 Sterner Design, LLC 1.  # of corners 2.  # of baths + plumbing length 3. shades as “carved” elements
  74. 74. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC A lot of complexity here = a lot of cost
  75. 75. Copyright © 2017 Sterner Design, LLC Back to the drawing board …
  76. 76. Copyright © 2017 Sterner Design, LLC The revised schematic design
  77. 77. Copyright © 2017 Sterner Design, LLC Fewer corners + simpler plumbing + shading as additive
  78. 78. Copyright © 2017 Sterner Design, LLC % cost Original Alternative A Alternative B A Small Square footage (gross) 3,520 3,173 3,192 2,833 Sq. ft. concrete wall 19% 4,586 3,750 3,660 3,500 Sq. ft. glazing 10% 550 600 590 550 Sq. ft. green roof 10% 1,640 880 1,672 840 Sq. ft. hollow core precast 7% 2,432 2,293 2,432 2,033 Lin. ft. tunnel 5% 64 56 48 48 Sq. ft. exterior cladding 2% 3,022 3,683 2,496 2,200 Estimated cost (JH) $729,400 Estimated cost (CS) $547,592 $501,896 $524,041 $458,245 Less envelope area = less cost
  79. 79. Copyright © 2017 Sterner Design, LLC Less envelope area = better performance
  80. 80. Copyright © 2017 Sterner Design, LLC ENCLOSURE ! DESIGN + MATERIALS FOUNDATION ! DESIGN So: we have 2x the insulation and 3x the airtightness of a standard house, but spent only marginally more on the enclosure
  81. 81. Copyright © 2017 Sterner Design, LLC 2.
 Think about labor.
 
 (MATERIALS)
  82. 82. Copyright © 2017 Sterner Design, LLC Structure Insulation Air barrier ICFs = 3-in-1 solution: structure + insulation + air barrier
  83. 83. Copyright © 2017 Sterner Design, LLC The concrete forms a continuous air barrier Copyright © 2017 Sterner Design, LLC
  84. 84. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC
  85. 85. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC
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  91. 91. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC A crew of 2 just installed •  The formwork for the concrete structure •  R-45 continuous wall insulation •  A high-quality air barrier = significant labor cost savings
  92. 92. Copyright © 2017 Sterner Design, LLC 3.
 Use efficiency to reduce
 HVAC costs.
 
 (INTEGRATIVE DESIGN)
  93. 93. Copyright © 2017 Sterner Design, LLC Integrative Design in theory: Better performance at LESS cost
  94. 94. Copyright © 2017 Sterner Design, LLC How it worked here: Tiny heating load ! smaller, cheaper heating system Good passive design ! no A/C
  95. 95. Copyright © 2017 Sterner Design, LLC Designing the Enclosure Thermal, air, and vapor control
  96. 96. Copyright © 2017 Sterner Design, LLC 1.
 Thermal control
  97. 97. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC Continuous insulation R-45 walls R-60 roof
  98. 98. Copyright © 2017 Sterner Design, LLC Window detail: Excellent windows (Zola) + Overinsulation Copyright © 2017 Sterner Design, LLC ! SEE THE DETAILS @ WWW.IOWANEST.COM
  99. 99. Copyright © 2017 Sterner Design, LLC 2.
 Infiltration control
 (air barrier)
  100. 100. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC Air barrier = ICF concrete core + AB membrane over roof sheathing +
 good details
  101. 101. Copyright © 2017 Sterner Design, LLC Window detail: Siga tapes on interior
 from window to plywood buck, and from buck to ICF ! SEE THE DETAILS @ WWW.IOWANEST.COM
  102. 102. Copyright © 2017 Sterner Design, LLC 4.
 Vapor / moisture control.
  103. 103. Copyright © 2017 Sterner Design, LLC Why is this hard?
 1. High insulation = cold surfaces
 2. Cold surfaces + moisture = condensation = rot + mold = " AND, in the Midwest …
  104. 104. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC Summer = Cold inside, Humid outside ! Vapor drive inward
  105. 105. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC Winter = Cold outside, Humid inside ! Vapor drive outward
  106. 106. Copyright © 2017 Sterner Design, LLC The solution: •  Insulate potential condensation surfaces •  Use air barriers to keep moisture from getting into assemblies (most moisture travels via air movement, not diffusion) •  Don’t trap moisture in / let assemblies dry
  107. 107. Copyright © 2017 Sterner Design, LLC Strategies: •  Breathable assemblies •  Insulate sheathing" (keep above dewpoint) •  Ceiling air barrier Copyright © 2017 Sterner Design, LLC
  108. 108. Copyright © 2017 Sterner Design, LLC Copyright © 2017 Sterner Design, LLC To be continued … ! STAY UP-TO-DATE @ WWW.IOWANEST.COM
  109. 109. Copyright © 2017 Sterner Design, LLC Thank you! carl@sternerdesign.com www.sternerdesign.com www.iowanest.com

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