1. 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

2. NAHB Research Center Industry
Partnership
Mission:
Promote innovation to
improve the quality,
durability, affordability,
and environmental
performance housing.
2

3. Outline
 High Performance Frame Wall System
 Framing Details
 Air Sealing Details
 Whole House Examples
3

4. 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
4

5. 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
5

6. What is the Question?
 Can we advance framing further??
6

7. 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. 7

8. Specific Technical Approach
 Insulated 3-stud corners
 Rim headers
 Continuous drywall approach
 Modular Fireplaces
8

9. The Solutions . . .
9

10. Advanced Wall Framing Design
 Cost effectively go from 2x4 to 2x6 wall
design
10

11. Framing: Advanced Design
 Typical Wall
 Stud Count: 52
 Framing: 20%
 Energy Efficient Wall
 Stud Count: 37
 Framing: 13%
11

12. Insulated 3-Stud Corner
12

13. Interior Wall Intersection
13

14. Integrated Rim Header & Load Path
14

15. 15

16. Integrated Rim Header
16

17. Integrated Rim Header
17

18. Modular Fireplace Construction
18

19. Fireplace Construction
Typical
Modular
19

20. Framing & Air Sealing:
Offset Interior Wall Intersection
20

21. Continuous Drywall
Courtesy of K-Hovnanian
21

22. Continuous Drywall
22

23. Whole-House Solutions
23

24. 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
24

25. 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
25

26. 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
26

27. Factory installed sheathing
gaskets
Factory installed sheathing tape
27

28. Sealed air barrier
adjacent to garage
knee wall
Sealed air barriers at fireplace framed cavity and
coffered ceiling beyond
Sealed Air Barriers
28

29. Partition wall held 1” at exterior for
continuous drywall method
Top plates foamed from attic
Air Sealing Methods
29

30. Sealed top plates and air
barrier
Sealed top plates of partition
wall and exterior wall
Sealed Top Plates
30

31. 31

32. 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
32

33. Incremental Cost Analysis
33
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)

34. 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
34

35. 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%
35

36. 30% New Construction Test House
 Three-story Queen Anne
style single family design
 Finished basement & loft
 Mixed-Humid Climate
Zone 4
 Production builder
36

37. 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
37
Cost Effective Energy Solutions

38. 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
38

39. Interior wall held back so
that exterior wall receives
continuous drywall
Limit of 2-ply
rim joist
header
Rim Joist Header & Continuous Drywall
39

40. Rim headers and HVAC supply trunk cutout 402x6 panelized walls at 24” o.c,
Floor joists at 24” o.c. with
factory installed mechanical
chase cutouts

41. 2nd floor
1st floor
3rd floor
Duct layout in 3-D plan to assure
accurate and consistent installation
41

42. House wrap as air seal,
taped at top and bottom
42
Air Sealing

43. Continuous Drywall Approach
 Seal drywall at:
 Top plate
 Bottom plate
 Around receptacles
 Can use:
 Foam
 Gasket
 Caulking
43

44. 44Tested insulation density
Walk-thru
revealed
missing
insulation Thermal
and air
barrier
Elastomeric air seal at:
• Top/ bottom plates
• Wall junctions
Airtight Drywall Approach

45. 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
45

46. 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%
46

47. 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
47

48. 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

49. What was learned?
 Success!
 More work . . .
 Builder’s Guide
 Moisture performance
49

50. Related Research . . .
50

51. Wind Resistance of Walls with
Exterior Foam
Stud failure at
predrilled hole
51

52. Moisture Research: Test Huts

53. Moisture Research: Field Monitoring
Moisture
Sensors
Moisture
Content
Screws
Internal
Sensor
Antenna
53

54. Looking Ahead . . .
54

55. 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
55

56. 56

57. 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!