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Website Notice Requesting Public Input on Further Analysis Related to 2004/2006 IECC/IRC Residential Code Change Proposals
The U.S. Department of Energy proposed an extensive simplification of the 2003 International Energy Conservation Code (IECC) and the energy chapter of the International Residential Code (IRC) at the ICC Code Development hearings in 2003. The Department's proposal was accepted at the 2003 Code Development hearings, but was modified in the IECC by amendments raised from the floor. These "floor amendments" increased wall R-value requirements in several climate zones and extended trade-off limits for U-factors and solar heat gain coefficients (SHGC) on fenestration products in several climate zones. Similar floor amendments were not proposed for the energy chapter of the IRC.
In the absence of any technical documentation for the floor amendments, the Department conducted an initial analysis and posted the results on the website February 23, 2005. The Department withdrew this initial analysis on September 26, 2005, and stated that "more data is needed to fully address the potential cost impacts of various wall insulation options and the potential opportunity for the use of insulating sheathing in all locations, including high seismic and hurricane zones. DOE will use a review and comment approach before finalizing any analysis on the current IECC and IRC fomulations."
The increased wall requirements were rescinded in the 2006 IECC, and the Department is not aware that proposals of this kind are under consideration at the present time. If such proposals were generated the Department still believes more data would be required before finalizing an analysis of wall insulation options such as those considered in 2004. The Department is requesting additional data and requesting review and comment on the data available. This data, along with stakeholder comments, will be beneficial if and when a more comprehensive analysis is needed.
Therefore, the Department specifically requests information from interested and affected parties related to the following exterior wall insulation topics:
- The price and availability of medium- and high-density fiberglass batt insulation-what are the raw material costs of fiberglass products that can fit within 2x4 and 2x6 wall cavities to achieve R-values of 15 and 21, respectively?
DOE's current best information: An old estimate from Oregon, which has required R21 in its state code for many years, is $0.10/ft2. The 2001 California Database for Energy Efficient Resources (DEER) reports an incremental cost of $0.44/ft2 for R-21 compared to R-19 and $0.42/ft2 for R-15 compared to R-13. Cost data can also be obtained from retailers such as Home Depot and Lowe's. These sources in September 2005 quoted incremental costs of $0.17 to $0.30/ft2 for R-15 and R-21 compared to R-13 and R-19 (Pacific Northwest stores).
- The material and labor costs associated with various insulating sheathing configurations, including costs associated with increased wall thickness when insulating sheathing thicker than standard wood panels are used.
DOE's current best information: DOE has sampled regional material costs at the Lowe's Home Improvement website (www.lowes.com, July 2005):
Table 1
Retail Sheathing Prices (Four-by-Eight Ft. Panel)
| City | 1/2" Extruded Polystyrene | 7/16" OSB |
|---|---|---|
| Atlanta (30301 | $10.38 | $10.99 |
| Dallas (75202) | $10.38 | $10.88 |
| Raleigh (27601) | $10.38 | $10.99 |
| Kansas City MO (64101) | $10.38 | $10.88 |
| Chicago (60601) | $6.77 | $9.86 |
| Boston (02101) | $10.38 | $11.59 |
| Minnesota (55401) | $6.77 | $9.86 |
| Los Angeles (90101) | -- | $10.99 |
| Seattle (98101) | -- | $10.99 |
| Notes: EPS not listed on the website in Western locations. | ||
R.S. Means 2005 cost data reports a $0.28 labor cost for the installation of 1/2" plywood (06160) and a slightly lower $0.24 labor cost for 1" XPS. R.S. Means does not include 1/2" XPS.
Based on these sources, the total installed cost of XPS insulating sheathing appears to be comparable to the cost of the OSB that it typically replaces, assuming no construction changes other than OSB panels at the corners are necessary to comply with bracing requirements.
- The number of new homes that incorporate insulating sheathing and the most common configurations in various geographical regions.
DOE's current best information: DOE is aware of the following data. The Engineered Wood Journal 2005, http://www.apawood.org/level_b.cfm?content=pub_ewj_arch_s02_up) reports that "Foam sheathing commands 20 and 15 percent shares, respectively, of the single-family and multifamily markets." Ten percent of building designs entered into DOE's REScheck-Web software http://energycode.pnl.gov/REScheckWeb/ have walls with at least R-2 insulating sheathing. Table 2 provides limited regional data on the use of insulating sheathing in new construction found from survey data. This indicates that insulating sheathing is more common in some regions than in others. During a period of high wood panel costs in early 2004, NAHB reported that "many builders have switched" to non-structural sheathing (NAHB Nation's Building News Online. March 15, 2004).
Table 2
Prevalence of Insulating Sheathing Walls
in New Residental Contruction
| State/Region | Number of Houses Surveyed | Year | Percent with Insulating Sheathing |
|---|---|---|---|
| Wisconsin | 105 | 1998/1999 | 46% |
| Massachusetts | 186 | 2000 | 3.5% |
| Pacific Northwest | 366 | 1998 | Rare (<5%) |
- The bracing options available to builders using insulating sheathing and their associated costs. Of particular concern is bracing in high seismic and hurricane regions and for wall configurations with limited space for panel bracing (e.g., walls around garage doors, walls with windows in/near corners).
- Any practical R-value limits for various types of insulation installed in wall stud cavities-what are the tested R-values per inch of commercially available materials/products?
- Documentation on any quantifiable differences in air-leakage performance between various cavity insulation types.
- Other information related to the energy and energy-cost performance of various wall options.
DOE's current best information: The following studies are known to the Department.
Cellulose Insulation Manufacturers Association. 1990 University of Colorado, Denver Study. http://www.cellulose.org/cellulose_benefits.html.
Energy Design Update. April 2005.
NAHB Research Center. Field Demonstration of Alternative Wall Insulation Products. November 1997.
Pennsylvania State University. A Field Study of the Effect of Insulation Types on the Air Tightness of Houses. G.K. Yuill, Ph.D., Department of Architectural Engineering, 1996.
Union Electric. Research and Development Project, "Maple Acres." St. Louis, MO. William Conroy, Division Marketing Supervisor, 1995.
DOE requests that technical data, published studies, and other substantiating information be provided with comments. Comments were due by February 22, 2006, to:
Stephen P. Walder
Architect, Office of Building Technologies
EE-2J/Forrestal Building
U.S. Department of Energy
1000 Independence Ave, S.W.
Washington, DC 20585
Phone: 202-586-9209
Fax: 202-586-4617
Email: Stephen.walder@hq.doe.gov