Internal Roof and Attic Thermal Radiation Control Retrofit Strategies for Cooling-Dominated Climates A. Fallahi, H. Durschlag, D. Elliott, J. Hartsough, N. Shukla, and J. Kosny Fraunhofer Center for Sustainable Energy Systems December 2013 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, subcontractors, or affiliated partners makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. 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Box 62 Oak Ridge, TN 37831-0062 phone: 865.576.8401 fax: 865.576.5728 email: mailto:[email protected] Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: 800.553.6847 fax: 703.605.6900 email: [email protected] online ordering: http://www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste Internal Roof and Attic Thermal Radiation Control Retrofit Strategies for Cooling-Dominated Climates Prepared for: The National Renewable Energy Laboratory On behalf of the U.S. Department of Energy’s Building America Program Office of Energy Efficiency and Renewable Energy 15013 Denver West Parkway Golden, CO 80401 NREL Contract No. DE-AC36-08GO28308 Prepared by: A. Fallahi, H. Durschlag, D. Elliott, J. Hartsough, N. Shukla, and J. Kosny Fraunhofer Center for Sustainable Energy Systems (CSE) Building Energy Efficiency Group 5 Channel Center Street Boston, MA 02210 NREL Technical Monitor: Chuck Booten Prepared under Subcontract No. KNDJ-0-40345-02 December 2013 iii [This page left blank] iv Contents List of Figures ............................................................................................................................................ vi List of Tables ............................................................................................................................................ viii Abbreviations ............................................................................................................................................. ix Acknowledgment ........................................................................................................................................ 1 Executive Summary .................................................................................................................................... 2 1 Introduction ........................................................................................................................................... 4 2 Field Testing .......................................................................................................................................... 8 2.1 Instrumentation ..................................................................................................................13 2.2 Radiation Control Technology Installations ......................................................................17 2.2.1 Radiant barrier with enclosed airspace ..................................................................17 2.2.2 Interior Radiation Control Coating (IRCC) ...........................................................18 3 Experimental Data Analysis .............................................................................................................. 20 3.1 External and Internal Air Temperature Comparisons ........................................................20 3.2 Experimental Attic Air Temperature Comparisons ...........................................................29 3.3 Experimental Heat Flux Comparison.................................................................................44 4 Energy Modeling ................................................................................................................................. 47 4.1 Model Description .............................................................................................................47 4.2 Calibration of Whole Building Energy Model ...................................................................50 4.3 Prediction of the Cooling Energy Consumption ................................................................53 4.4 Modeling Results ...............................................................................................................53 5 Cost Effectiveness Analysis .............................................................................................................. 56 6 Conclusions ........................................................................................................................................ 58 References ................................................................................................................................................. 60 Appendix A- Historical Energy Consumption Data ............................................................................... 62 v List of Figures Figure 1. Location of site. ........................................................................................................................... 8 Figure 2. Location of thermistor arrays and heat flow transducers inside the tested attics (Right); Bird view image of the duplexes in Austin, TX (Left). ....................................................................... 9 Figure 3. Estimated brick wall construction: 2 in. brick, 1 in. air gap, ½ in. OSB, 2×4 stud wall with batt insulation, gypsum wall board (left); Estimated clapboard siding: clapboard, battens, ½ in. OSB, 2×4 stud wall with batt insulation, gypsum wall board (right). ............................................ 10 Figure 4. Existing insulation conditions in Duplex 1. Note the inconsistent levels of loose-fill insulation. ............................................................................................................................................ 10 Figure 5. Existing insulation conditions in Duplex 2. Note the inconsistent levels of loose-fill insulation. ............................................................................................................................................ 11 Figure 6. Existing insulation conditions in Duplex 2 (left) and Duplex 1 attic over living space (above right) and over garage (below right). ................................................................................... 12 Figure 7. Visible gaps around ducts entering attic. .............................................................................. 12 Figure 8. Location of the vents for attics over living spaces in Duplex 1. .......................................... 13 Figure 9. Location of the vents for attics over living spaces in Duplex 2. .......................................... 13 Figure 10. Diagrams of the attic sensor distributions for a RB combined with an enclosed reflective air space (upper diagram), and IRCC and baseline (lower diagram). .......................... 15 Figure 11. Thermistors installed on interior, exterior and attic to capture surface temperatures. .. 16 Figure 12. DAQ Components. .................................................................................................................. 17 Figure 13. Installation of RB with enclosed airspace from Fi-Foil Company (Silver Shield). ........... 18 Figure 14. Installation of IRCC from Solec-Solar Energy Corporation (LO/MIT-II MAX) (left) and from STS Coating, Inc. (HeatBloc-Ultra) (right). .............................................................................. 19 Figure 15. Measured exterior air temperature on one of the test houses. .......................................... 21 Figure 16. Average daily roof surface temperatures recorded during the April measure period. ... 22 Figure 17. Average daily roof surface temperatures recorded during the June/July measure period.23 Figure 18. Average daily roof surface temperatures recorded during the July/August measure period. .................................................................................................................................................. 24 Figure 19. Maximum roof surface temperatures recorded during the April measure period. .......... 25 Figure 20. Maximum roof surface temperatures recorded during the June/July measure period. .. 26 Figure 21. Maximum roof surface temperatures recorded during the July/August measure period.27 Figure 22. Average interior air temperatures recorded during the April measure period. ................ 28 Figure 23. Average interior air temperatures recorded during the June/July measure period. ....... 29 Figure 24. Example of attic air temperatures