2012 09 - eeba nahbrcip-prod_bldr struct design
TRANSCRIPT
A Production Builder’s Guide to Energy Efficient Structural Design
Energy Efficient Framing Systems
EEBA Excellence in Building Conference
Tuesday, September 25, 2012
Salon C
Amber Wood, NAHBRC
NAHB Research Center Industry Partnership
Mission:
Promote innovation to improve the quality, durability, affordability, and environmental performance housing.
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Outline
High Performance Frame Wall System
Framing Details
Air Sealing Details
Whole House Examples
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4.
Infrastructur
e
Developmen
t
4.
Infrastructure
Development
3.
Effective
Guidance
and Tools
3.
Effective
Guidance and
Tools
2.
House-as-a-
System
Business Case
2.
House-as-a-
System
Business Case
1.
Advanced
Technologie
s &
Practices
1.
Advanced
Technologies &
Practices
Building America Innovations
This research is paving the way for key innovations:
Energy Efficient Components
New Home Whole-House Packages
High Performance Home Solutions
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Builder Resources
Climate-specific considerations Code-related considerations Detailed drawings “Wrong ” and “right” way-to-do-it examples Training materials Technical references
Link to DOE resources:
www.buildingamerica.gov
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What is the Question?
Can we advance framing further??
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Why Do We Care?
Goal . . . Build “high performing homes” that are Energy efficient
Durable
Comfortable
Healthy to live in
Safe
Affordable
Achievable
In other words . . . Green.
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Specific Technical Approach
Insulated 3-stud corners
Rim headers
Continuous drywall approach
Modular Fireplaces
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The Solutions . . .
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Advanced Wall Framing Design
Cost effectively go from 2x4 to 2x6 wall design
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Framing: Advanced Design
Typical Wall Stud Count: 52
Framing: 20%
Energy Efficient Wall Stud Count: 37
Framing: 13%
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Insulated 3-Stud Corner
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Interior Wall Intersection
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Integrated Rim Header & Load Path
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Integrated Rim Header
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Integrated Rim Header
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Modular Fireplace Construction
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Fireplace Construction Typical
Modular
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Framing & Air Sealing: Offset Interior Wall Intersection
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Continuous Drywall
Courtesy of K-Hovnanian
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Continuous Drywall
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Whole-House Solutions
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30% New Construction Test House
Single-story slab-on-grade single family design
Mixed-Humid CZ 4
Production builder
Same model with same floor plan and orientation two lots away
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Design Considerations Solution
Improved Air Sealing Detailed air sealing improvement measures balanced with cost and
consistency of installation
Increased Insulation Optimized framing plus exterior structural insulation to increase
thermal performance
Improved HVAC system efficiency, air delivery, & occupant comfort for single-story slab-on-grade designs
Redesigned HVAC system: Equipment located in conditioned space Return duct simplified & located in conditioned space Supply duct deeply buried, well sealed, trunk located within truss
chase
Quality Assurance & Control
Choose construction details with consideration for builder & trade approaches
Construction specifications, preparatory meetings, and site monitoring
Repeatable Design Enhanced features to optimize performance and cost as well as
ensure consistent installation
Cost Effective Energy Solutions
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Thermal Envelope Feature Standard Practice NCTH Enclosure Enhancements
Foundation Slab on grade 2’ perimeter insulation, R-10
Standard plus: R-10 edge insulation
Walls 2x4 frame, 16” o.c. R-13 batt insulation, Class 1
Standard plus: Panelized walls 1” Structural Insulated Sheathing (SIS), R-6.5 Continuous drywall method 3-stud corners
Windows U = 0.37 U = 0.34, SHGC = 0.26
Air Sealing
Wall bottom plates caulked Penetrations sealed Window rough openings
foamed
Standard plus: SIS panels
– Gasketed at top & bottom plates – Taped seams – Provides WRB & air barrier
Foam over top plates from attic Foam over HVAC trunk & register boots Framed cavities & knee wall air barriers Garage-side drywall & electrical boxes
Roof/attic (vented) Truss, top chord overhang R-38, loose fill fiberglass
Raised heel truss, cantilevered overhang R-49, loose fill fiberglass
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Factory installed sheathing gaskets
Factory installed sheathing tape
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Sealed air barrier adjacent to garage knee wall
Sealed air barriers at fireplace framed cavity and coffered ceiling beyond
Sealed Air Barriers
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Partition wall held 1” at exterior for continuous drywall method
Top plates foamed from attic
Air Sealing Methods
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Sealed top plates and air barrier
Sealed top plates of partition wall and exterior wall
Sealed Top Plates
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Estimated Annual Source Energy (Mbtu/yr)
Estimated Annual Utility Bills ($/yr)
End Use BAB NCTH Savings BAB NCTH Savings
Fixed Charges 192 192 0
Space Heating 121.3 74.2 39% 1,458 891 567
Space Cooling 7.5 3.7 50% 94 47 47
HVAC fan 5.7 3.4 40% 72 43 29
Hot Water 21.7 11.0 50% 261 132 130
Lighting 24.2 19.0 21% 306 240 65
Appliances & MELs 61.6 55.0 11% 776 694 83
OA Ventilation 3.2 1.9 40% 40 24 16
Total 245.2 168.2 31% $3,200 $2,263 $937
Total (size adjusted) 243.3 168.2 31%
Site Generation (49.4) ($880)
Net 243.3 118.8 51% $3,200 $1,383 $1,817
Simulated Energy Savings – BEopt v1.1
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Incremental Cost Analysis
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Group Category
Builder's Net Additional Cost
(labor & materials)
Adjusted (no framing
credit)
Framing
1" SIS sheathing $ 1,591
Panelized walls credit $ (3,320)
Truss (raised heel & HVAC chase, simplified without coffers, adjusted for site built coffers & air barriers) $ 0
Roof/attic R-49 insulation $ 525
Air sealing Spray foam top plates & duct $ 1,300
Windows Improved efficiency rating $ 150
Jamb extensions $ 350
HVAC Entire System $ 238
Plumbing Tankless direct vent water heater $ 350
Lighting 100% CFL $ 280
Total Additional cost of options $ 1,464 $ 4,784
Net total Adjusted for 10% builder margin $ 1,627 $ 5,316
Net Monthly Cost
Mortgage net monthly cost $ 11 $ 35
Utilities net monthly cost $ (78) $ (78)
Net monthly cost $ (67) $ (43)
Performance Testing
Performance Metric Standard Model NCTH Change Units
House Size 2,587 2,498 - 3%
sq.ft.
House Volume 23,542 22,732 cu.ft.
Infiltration
2,717 1,021
- 61%
CFM50
6.9 2.7 ACH50
0.37 0.15 ACHnat
Normalized Infiltration 1.05 0.41 CFM50/sq.ft.
Total Duct Leakage 165 85 - 48% CFM25
Duct Leakage to Outside 74 0 - 100% CFM25
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Performance Monitoring Performance Metric
Dec ‘09 – Jan ’10 Standard Model 30% Test House Change
Gas Heating Energy (therms) 286 137 - 52%
Furnace Electricity (kWh) 335 145 - 57%
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30% New Construction Test House
Three-story Queen Anne style single family design
Finished basement & loft
Mixed-Humid Climate Zone 4
Production builder
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Design Considerations Solution
Improved Air Sealing Detailed air sealing improvement measures balanced with
implementation cost and consistency of installation
Increased Insulation Optimized 2x6 framing with densely blown fiberglass insulation
increased thermal performance and reduced framing factor
Improved HVAC system efficiency, air delivery, & occupant comfort
Reduced the number of HVAC systems from the traditional two systems to one
Redesigned floor plan, framing, and ducts to locate entire HVAC and distribution system in conditioned space for significant savings
Improved equipment operation efficiencies Improved ventilation, filtration, and occupant comfort
Quality Assurance & Control
Planning stage design reviews included practical input from WHI, vendors, and trade partners
Developed construction details and specifications for plan set Established construction monitoring points (review, inspection, test)
Repeatable Design Specified features which optimized performance, cost, & practical
implementation
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Cost Effective Energy Solutions
Thermal Envelope
Feature Standard Practice NCTH Enclosure Enhancements – Standard Plus
Foundation Inground basement R-10
Inground basement R-13
Walls 2x4 frame, 16” o.c. R-13 batt insulation, grade 1
Panelized walls 2x6 frame, 24” o.c., optimized framing Structural rim joist headers R-24 blown fiberglass WRB installed as air barrier
Windows U = 0.35, SHGC = 0.35 U = 0.31, SHGC = 0.28
Air Sealing
Wall bottom plates caulked Penetrations sealed Window rough openings foamed
Sprayed sealant as primary air seal at all OSB seams and framing intersections
Sprayed sealant as gaskets at framing behind continuous drywall
Redundant air barriers – sealant, continuous drywall and house wrap, taped
Roof/attic (partially vented)
Truss, top chord overhang R-38, loose fill fiberglass
Raised heel truss with 2’ overhang R-49 blown fiberglass with full depth at eaves and
sloped ceilings
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Interior wall held back so that exterior wall receives continuous drywall
Limit of 2-ply rim joist header
Rim Joist Header & Continuous Drywall
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Rim headers and HVAC supply trunk cutout 40 2x6 panelized walls at 24” o.c,
Floor joists at 24” o.c. with factory installed mechanical chase cutouts
2nd floor
1st floor
3rd floor
Duct layout in 3-D plan to assure accurate and consistent installation
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House wrap as air seal, taped at top and bottom
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Air Sealing
Continuous Drywall Approach
Seal drywall at:
Top plate
Bottom plate
Around receptacles
Can use:
Foam
Gasket
Caulking
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44 Tested insulation density
Walk-thru revealed missing insulation Thermal
and air barrier
Elastomeric air seal at: • Top/ bottom plates • Wall junctions
Airtight Drywall Approach
Quality Assurance Plan – Inspect, Test, Retest
Performance Metric NCTH Units
House Size 4,441 SF finished area
4,568 SF conditioned area
House Volume 41,847 CF
Infiltration
Test 1A Test 2B Final
2,400 1,380 1,335 CFM50
3.4 2.0 1.9 ACH50
0.17 0.10 0.10 ACHnat
0.53 0.30 0.29 CFM50/SFcfa A Prior to trim and sealing of all penetrations but after sheetrock installation B After access panels and other knee walls from the 3rd floor room to the attic were sealed C Final after all finishes complete
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Simulated Energy Savings – BEopt v1.1
Estimated Annual Source Energy (Mbtu/yr)
Estimated Annual Utility Bills ($/yr)
End Use BAB NCTH Savings BAB NCTH Savings
Space Heating 96.8 58.9 39.2% 1,425 867 39.2%
Space Cooling 26.5 17.0 35.8% 344 221 35.8%
Hot Water 23.7 14.5 38.8% 348 214 38.5%
Lighting 41.1 25.6 37.7% 533 333 37.5%
Appliances & MELs 75.9 71.0 6.5% 1001 936 6.5%
OA Ventilation 4.9 2.9 40.8% 63 38 39.7%
Total 268.7 190.0 29.6% $3,715 $2,608 29.8%
Total (size adjustment) 26.3 190.0
Site Generation (0.0) Savings (0.0) Savings
Net 242.4 190.0 21.6% $3,715 $2,608 29.8%
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Activity Category Builder's
Estimated Incremental Cost
Walls
2” x 6” wall studs R-24 blown in mesh fiberglass insulation
$ 3,088
Rim joist headers in lieu of wall headers Not estimated
Raised heel trusses Not estimated
Attic R-49 blown cellulose in attic $ 100
Air sealing Spray latex air seal $ 1,910
Windows Improved efficiency rating $ 0
Jamb extensions Not estimated
HVAC
Single HVAC system w/higher efficiencies Multi-zone duct system in conditioned space
$ 2,155
Supply side ventilation $ 600
Water Heating 74% efficient 50 gallon tank gas water heater $ 350
Lighting 80% CFL $ 126
Miscellaneous Appliances, etc. $ 1,434
Total Estimated cost of upgrades $ 9,763
Net Monthly Cost
Mortgage net monthly cost (7%, 30 years) $ 65
Utilities net monthly savings $ (92)
Net monthly cost/(savings) $ (27)
Incremental Cost Analysis
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Performance Testing
48 courtesy of www.winchesterhomes.com
Location Temperature (°F)
Jun 21, 8 am Jun 21, 4 pm Aug 17, 1 pm
1st floor at thermostat 70.6 71.6 72.2
2nd floor master bedroom 70.4 71.6 72.1
3rd floor bedroom 70.7 72.6 73.5
Basement recreation room 69.7 70.9 72.3
What was learned?
Success!
More work . . .
Builder’s Guide
Moisture performance
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Related Research . . .
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Wind Resistance of Walls with Exterior Foam
Stud failure at predrilled hole
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Moisture Research: Test Huts
Moisture Research: Field Monitoring
Moisture Sensors
Moisture Content Screws
Internal Sensor
Antenna
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Looking Ahead . . .
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Future Efforts Develop prescriptive methodology for use with
advanced framing details
Prescriptive tables for integrated rim header application
Concise list of advanced framing features
Training materials to educate code officials on aspects of advanced framing
Develop Builder’s Guide for High Performing Walls
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Amber Wood
NAHB Research Center
Manager, Energy Programs
400 Prince George’s Blvd
Upper Marlboro, MD 20774
301.430.6309
www.nahbrc.com • www.toolbase.org
Thank You!