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

awood@nahbrc.com

www.nahbrc.com • www.toolbase.org

Thank You!