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r Table 3. R-Values and Framing Effect Coefficients for Three Wall Configurations from Figures 4-6 Clear-Wall R-Value, Type of Configuration hf�°FBtu(mr%/IIO Framing Effect Coefficient, Wood Steel Wood Steel All Studs in Center(Figure 4) 9.50(1.67) 5.51 (0.97) 26.9 57.6 Equally Distributed(Figure 5) 9.35(1.65) 4.91 (0.86) 28.1 62.2 Equally Distributed Plus Header and Sill(Figure 6) 9.32(1.64) 4.77(0.84) 28.3 63.3 tg-." • Wood-framed structures are less sensitive to differences in framing configuration intensity then steel-framed / structures. a • Wood-frame walls are more sensitive than steel struc- r4/ tures to imperfections in the wall-cavity insulation. If a g� 1s - small air cavities between wood structural members are g 5/ 315 4.17 •a left un-insulated, the overall wall thermal performance a/— can be compromised almost to the.level of steel-framed walls. rc a� • Thermal insulation installed in the internal areas 2 between steel-stud flanges doesn't bring significant �1 111 1111 improvements of the steel-stud wall thermal perfor- 0on - mance. Enpyair gaps Inaulaeon hi spacing All cavities Insulated 0 wood*hide te steel awds REFERENCES AISI 2003. Steel in Residential Construction, Publication Figure 10 Calculated clear-wall R-values for wood and R6-9405,American Iron and Steel Institute, 1101 7th steel framed walls. Street NW,Washington,DC 20036-4700. AISI. American Iron and Steel Institute, http:// www.steeLorg/facts/residential.htm cavities do not follow nominal framing spacing and require ASHRAE 1989.ASHRAE/IES 90.1-1989"Energy Efficient custom cutting and fitting of the batt insulation.Possible solu- Design of New Buildings Except New Low-Rise Resi- dons to this problem involve application of blown-in-place dential Buildings—ASHRAE,Atlanta GA,ISSN 2336, cellulose,blow-in fiberglass insulation,or spray-applied foam. 1989 ASHRAE 1993. ASHRAE/IES 90.2-1993 "Energy-Effi- CONCLUSIONS cient Design of New Low-Rise Residential Buildings"— This paper presents experimental and numerical analysis ASHRAE,Atlanta GA,ISSN 1041-2336, 1993 of thermal effects of framing intensity on overall wall thermal ASHRAE. 2001. "ASHRAE Handbook: Fundamentals". performance in wood and steel-framed walls. In addition, Atlanta:American Society of Heating, Refrigerating consequences of installation imperfections in cavity insula- and Air-Conditioning Engineers,Inc. tion were analyzed from a thermal perspective.A series of hot- ASTM 1997. ASTM C 1363-97, Standard test method for box tests and computer simulations were conducted on wall "Steady-State Thermal Performance of Building assemblies representing current residential construction prac- Assemblies by Means of Guarded Hot Box",Vol 04.06. ticewith24%and27%framing factors.The following conclu- Carpenter S.C. Schumacher C. 2003. - "Characterization of sions can be derived from this work: Framing Factors for Wood-Framed Low-Rise Residen- tial Buildings"ASHRAE Transactions v 109,Pt 1.Feb. • Center-of-cavity R-values are significantly higher from 2003. the measured clear-wall R-values. The authors suggest CEC 200IA. "Characterization of Framing Factors for Low- that they shouldn't be directly used for code approvals, Rise Residential Building Envelopes in California" - • load calculations,or whole-building energy simulations. Public Interest Energy Research Program:Final Report,kkorThe addition of a''/e-in.(1.9-cm)thick extruded polysty- Publication Number: 500-02-002,Dec 2001. rene foam board to steel-frame walls had a measured CEC 2001B. "2001 Energy Standards for Residential and clear-wall R-value less than that of a similar wood- Non-Residential Buildings",California Energy Corn- frame wall without foam-board sheathing. mission Title 24,Aug 2001. 8 Buildings X