Advanced Framing for Passive House Katy Hollbacher, P.E. | beyondefficiency.org June 28, 2009 Hosted by: Passive Buildings California Berkeley, California
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Advanced Framing for Passive House
Katy Hollbacher, P.E. | beyondefficiency.org June 28, 2009
Hosted by: Passive Buildings California Berkeley, California
Goals for Today
2
Typical structural approach & issues
Advanced Framing definition
Benefits & relevance to Passive House
How to do it!
Siegel & Strain
Typical Engineering Approach
3
Linear process: little or no collaboration
Lack of understanding of each others’ issues “Architect designs things that
are expensive to engineer” “Engineer doesn’t have any
sense of aesthetics” Ignoring of energy &
resource implications
Resource Waste
4
What is T24 ‘framing factor’? 25% (!) Wasted resources Added cost: materials, labor &
waste management
Energy Loss
5
More wood= less insulation More stuff=
Harder to insulate Harder to air seal (Harder to get PH cert!)
U.S. Department of Energy: improve a wall’s effective R-value up to 30% save 3-5% on heating and cooling costs
Framing Comparison
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USDE study:
What Is Advanced Framing?
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Systems approach to design, engineering, and construction of wood-framed structures that: Reduces lumber use Minimizes wood waste Maximizes a structure’s thermal efficiency…
While maintaining structural integrity and meeting building codes!
Advanced Framing Principles
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① Consider energy efficiency when designing the structural system
② Optimize layout for efficient material use ③ Use structural-rated wood materials to their
full approved capacities ④ Eliminate structural materials where non-
structural materials are adequate ⑤ Reduce the structural redundancies inherent
with conventional stick framing
Advanced Framing Measures
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Modular Layout
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Lay out building on two foot module: Maximize efficiency of 24 inch
framing and 4x8 sheet goods Reduce materials, labor & waste Increase energy performance
Keep plans simple Place openings on module Provide detailed framing elevs.
U.S Department of Energy
Framing Greater than 16” o.c.
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19.2” or 24”
CBC Table 2308.9.1"
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Energy Heels on Roof Trusses
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General rule-of-thumb: 75% of attic insulation
height at outer edge of ext. wall
More for Passive House?
Structural considerations
Headers Sized for Load
14
Rather than one option for worst-case scenario None where there’s no load!
Yes
No
Insulated Headers
15
Header Hangers
Jack/trimmer studs typically used to carry header loads
Replace with framing anchors when adequate (often OK when replacing single jack stud)
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Open Wall Corners
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3 or 4 studs typically used! Use 2-stud detail with
non-structural backing to support drywall per CBC 2308.9.2. Backing can be wood,
specified sheathing or panel materials, and “other approved devices”
How do I start?
18
Read Building Science Corp’s Using Wood Efficiently: From Optimizing Design to Minimizing the Dumpster research report: www.buildingscience.com/documents/reports
Read NRDC’s Efficient Wood Use in Residential Construction handbook: www.nrdc.org/cities/building/rwoodus.asp
Develop and discuss Advanced Framing goals in initial meetings
Barriers to Advanced Framing
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Architect: it will limit my creativity and design options
Engineer: I don’t want to do things a new way. I like to overdesign because I know what can happen in the field.
Builder: I don’t want to introduce new techniques that might concern the inspector and slow down the project.
Clients: more wood is better. I don’t want to pay more for added design & planning.
How to collaborate?
20
Identify project goals. Assemble quality team—and educate
them. How will accountability by measured or
verified?
Questions…
21 beyondefficiency.org
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