Steel Framing For The California Residential New Construction Market: Title 24 Energy Standards...
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Transcript of Steel Framing For The California Residential New Construction Market: Title 24 Energy Standards...
Steel Framing For The California Residential New Construction Market:
Title 24 Energy Standards
Robert Hammon, Ph.D.
Principal
ConSol
• 25 years providing energy solutions to production builders
• Title 24 Updates: CBIA Technical Support
• T24 Calcs for About 15% of Permits in CA
• Mechanical Design
• ComfortWise®
• Consulting
ConSol’s Consulting Dept
• US Department of Energy– Building America– Zero Energy Homes
• California Energy Commission – Zero Energy New Homes– Energy Code Training
• Utilities – Residential New Construction Program Support– Zero Energy New Homes– Energy Code Training– Community Energy Efficiency Program
• Manufacturers and Associations
Steel Framing and Energy Efficiency:Background
• What makes framing important to energy? – Heat transfer
• CA Energy Efficiency Standards (T24)– How deals with walls and ceilings
• What is typical wall construction?• How is a typical steel wall different?
Thermal Efficiency of Framing
• Heat Transfer:– R-value (resistance to heat transfer)– U-factor’s (heat transfer rate)– Thermal break/ thermal bridging (% knockout)– Percent of framing in wall cavity– Emissivity of exterior surface– Reflectance of exterior surface– Infiltration (uncontrolled airflow)
Title 24 (2005 Standards)
• Mandatory Minimum Measures– “R-13” wall– “R-19” ceiling
• Prescriptive Packages– Insulation, windows, equipment efficiencies– 16 Climate Zones
• Performance Approach– Less or equal energy as Prescriptive– Mandatory minimums apply
• Updated triennially
Typical Wall Construction
• Equivalent to 2005 Standards mandatory min– Material: Wood– Dimensions: 2 x 4 studs– Spacing: 16” o.c.– Percent framing: 24%– Cavity Insulation: R-13 Batt– Sheathing Insulation: None– Overall Performance: u-factor = 0.102
Typical Steel Framing
• C-studs w/ foam sheathing– Min R-5 sheathing to satisfy code mandate– Foam installed internal or external or both
• Similar construction technique as wood– 16” oc is 24 percent framing factor
• Overall performance: u-factor = 0.102
Common Questions
• Q1: What is the affect of increasing the spacing from 16 to 24 o.c.?
• Q2: How effective is foam sheathing?• Q3: What if I am using a blown-in insulation
rather than fiberglass batts?• Q4: How energy efficient is a steel wall in
comparison to a wood wall?• Q5: What is the impact of different types of foam
sheathing?
Steel Wall Efficiencies
Table IV.11 – U-factors of Metal Framed WallsCavity Rated R-value of Continuous InsulationInsulation Nominal R-0 R-2 R-4 R-6 R-7 R-8
Spacing R-Value: Framing A B C D E F 16 in. OC None Any 1 0.458 0.239 0.162 0.122 0.109 0.098
R-11 2x4 2 0.224 0.155 0.118 0.096 0.087 0.080 R-13 2x4 3 0.217 0.151 0.116 0.094 0.086 0.079 R-15 2x4 4 0.211 0.148 0.114 0.093 0.085 0.078 R-191 2x6 5 0.183 0.134 0.106 0.087 0.080 0.074 R-21 2x6 6 0.178 0.131 0.104 0.086 0.079 0.073 Foamed Plastic 2 x 4 14 0.218 0.152 0.116 0.094 0.086 0.079 or Cellulose 2 x 6 15 0.179 0.132 0.104 0.086 0.079 0.074 Insulation 2 x 8 16 0.157 0.119 0.096 0.081 0.075 0.070
24 in. OC None Any 24 0.455 0.238 0.161 0.122 0.109 0.098 R-11 2x4 25 0.210 0.148 0.114 0.093 0.085 0.078 R-13 2x4 26 0.203 0.144 0.112 0.092 0.084 0.077 R-15 2x4 27 0.197 0.141 0.110 0.090 0.083 0.076 R-191 2x6 28 0.164 0.123 0.099 0.083 0.076 0.071 R-21 2x6 29 0.161 0.122 0.098 0.082 0.076 0.070
Steel Attic Efficiencies
Table IV.4 – U-factors of Metal Framed Attic Roofs
Nominal Cavity Rated R-value of Continuous Insulation Framing Insulation R-0 R-2 R-4 R-6
Spacing Size R- Value: A B C D 16 in. OC 2x4 R-19 4 0.073 0.064 0.056 0.051
R-22 5 0.060 0.054 0.049 0.044 R-25 6 0.052 0.047 0.043 0.039 R-30 7 0.042 0.038 0.036 0.033 R-38 8 0.032 0.030 0.028 0.027 R-49 9 0.024 0.023 0.022 0.021
24 in. 2x4 R-19 14 0.065 0.057 0.051 0.047 R-22 15 0.055 0.049 0.045 0.041 R-25 16 0.047 0.043 0.040 0.037 R-30 17 0.039 0.036 0.034 0.031 R-38 18 0.030 0.028 0.027 0.025 R-49 19 0.023 0.022 0.021 0.020
* Continuous insulation shall be located at the ceiling or at the roof and be uninterrupted by framing.
CA 2005 Standards
• 15 percent more efficient than 2001 Standards (Statewide)
• Significant, fundamental changes in code– Energy vs. TOU (TDV) Energy
• Peak energy is valued higher than off-peak• Measures that reduce peak are more valuable• Wall efficiencies are more important under TDV
CA 2005 Standards - continued
• Cavity insulation installation quality assumed poor– Penalized unless HERS inspector can verify
quality– Credit for quality installation not available to
steel
• Framing factors change from 16% to 24%– Based on study of wood framed homes– Foam sheathing becomes more important
CA 2005 Standards - continued
• Efficiency of framing derived from Joint Appendix Section IV
Wall Efficiencies
Cavity EFS Wood U-factor Steel U-factor
13 0 0.102 0.217
13 4 0.068 0.116
13 8 0.052 0.079
21 0 0.069 0.178
21 4 0.051 0.104
21 8 0.041 0.073
Market Demands
• Meet code– CA 2005 Standards (Title 24)
• Low cost
• Low liability
• Contractor availability– Contractor driven market
Market Demand: CA Code
• Mandatory measures– Min efficiency of 2x4 wall with R-13 cavity
• Prescriptive packages– Wood framed walls with up to R-21 cavity
• Performance method– Evaluate overall building performance– Certain efficiency measures can be offset
against each other
Market Demand: Low Cost
• Labor and materials (L&M)• Energy design cost (EDC)
– External foam sheathing– Additional energy design measures
necessary to comply with performance
• L&M + EDC = Total installed cost (TC)• TC of traditional steel framing > TC of
traditional wood framing
Market Barriers
• Builders resistant to change• Building industry has a minimal understanding
of steel• CA minimum wall efficiency requires foam for
steel framed walls• Builder apprehension to foam sheathing (one-
coat stucco systems)
Market Barrier: Current Practice
• CA only 8% steel framing (AISI ‘02)• Designs are typically a stick for stick
replacement of wood• Exterior foam sheathing is necessary to meet
mandatory measures
Market Barrier: Education
• Steel has benefits
• Not parlayed to market
• Homebuyers– If it’s not visible…
• Builders – Don’t understand all the benefits– Assume stick for stick replacement to wood– Concerned about first costs
Market Barrier: Code
• 2005 Standards– Removed method for using alternative assemblies
(FORM 3R)– Efficiency of framing derived from Joint Appendix
• Thermal resistance of steel much less than wood– R-19 wood framed attic ~ R-30 steel framed attic
• Steel typically requires external foam sheathing
Solutions
• Advanced framing techniques• Additional exterior foam sheathing• Propose changes in the 2008 Standards• Convey message about benefits• Align with energy efficiency programs
Solution: Advanced Framing
• 19.2” or 24” o.c.
• Reduce Cost– Lower labor and material cost
• Increase Efficiency– Maximize the cavity insulation– Reduce the thermal bridging
• Knockout• 2x6• Lower conductance wall and exterior treatments
Solution: Foam Sheathing
• Sheathing is better than cavity insulation– Reduces the thermal bridging affect
• Typically R-3.8 per inch• Increase the thickness
– Probably the most effective of the solutions
• Improve the sheathing R-value– R-5 per inch is available
Solution: Messaging
• 2006 California Energy Star• Utility rebate programs• Federal tax credits
California Energy Star
• 2006 Energy Star Requirements• 15 percent better than CA standards• Thermal-bypass checklist (TBC)
– Indoor Air Quality– Insulation installation quality
• Benefit: Brand recognition• Drawback: Expensive to meet the TBC
Utility Rebate Programs
• Rebates for meeting Energy Star
• Benefits: Brand recognition + rebate
• Drawbacks: Rebate doesn’t offset cost of Steel– Also cost of Thermal Bypass Checklist
Federal Tax Credits
• 50% better than 2004 International Energy Efficiency Standards (IECC)
• Significantly built on or after Oct 1, 2005• Transferred to owner on or after Jan 1, 2006
through Dec 31, 2007• Required, third party inspector• Benefits: $2000 credit per qualified home
– Assist with additional costs
Solution: 2008 Standards
• AISI and SFA actively monitoring 2008• Monitor proposals for fairness and accuracy
– Attic model– Ventilation for IAQ
• Potential proposals– Adjust framing factor for 16 oc, 19.2 oc and 24 oc
• May require research and documentation
– Credit for quality installation of insulation in steel framing
• May require research and documentation
Summary
• 2005 Standards have significantly affected the entire industry
• Sheathing is a cornerstone in all cost efficient solutions
• Improve messaging• AISI and SFA are working for you...
Thank You!
Questions?
Rob Hammon, Ph.D.Principal, ConSol(209) 473-5000
7407 Tam O’ShanterStockton, CA 95210