This article focuses on understanding the temperature and heat flux fields in building roofs, and how they are modulated by the interacting influences of albedo and insulation at annual, seasonal and diurnal scales. High precision heat flux plates and thermocouples were installed over multiple rooftops of varying insulation thickness and albedo in the Northeastern United States to monitor the temperature and the heat flux into and out of the roof structures for a whole year. Our analysis shows that while membrane reflectivity (albedo) plays a dominant role in reducing the heat conducted inward through the roof structures during the warmer months, insulation thickness becomes the main roof attribute in preventing heat loss from the buildings during colder months. On a diurnal scale, the thermal state of the white roof structures fluctuated little compared to black roof structures; membrane temperature over white roofs ranged between 10°C and 45°C during summer months compared to black membranes that ranged between 10°C and 80°C. Insulation thickness, apart from reducing the heat conducted through the roof structure, also delayed the transfer of heat, owing to the thermal inertia of the insulation layer. This has important implications for determining the peak heating and cooling times.

a b s t r a c tThe advanced Princeton Roof Model (PROM) is evaluated and then applied to quantify the heat transferred through various modular roof structures over an entire year. The goal is to identify an optimal combination of roof reflectivity and insulation thickness that will reduce energy consumption and minimize cost. Meteorological data gathered over the Northeastern United States (Princeton, NJ) is used to force PROM. Our results reveal that for new constructions or for retrofits in the region, an R8.4 (around 46 cm thick roof insulation) white roof (assumed albedo = 0.6 or greater) would significantly reduce the combined heating and cooling load attributable to the roofs. The wintertime penalty of white roofs is also shown to be insignificant compared to their summertime benefits. The findings are pertinent to many other densely populated areas with comparable climates where, despite a much higher number of heating versus cooling degree-days, white roofs are overall advantageous. A cost optimization analysis found that doubling, tripling and quadrupling the insulation thickness from the baseline case of 5.08 cm (2 in.), at an albedo of 0.45, requires 13, 17 and 19 years, respectively, to recover the additional cost incurred.

I Prepared for DOE under contract No. W-7405-Eng-48 About the Cover This month's cover story (seep. I) reports on the background, design, and capabilities of the Portable Tritium Processing System (PYPS) currently being used to clean up and decontaminate the Laboratory's Tritium Facility under the Tritium Inventory Removal Project. The PTPS has four parts: a gas pumping and transport module, a gas analysis module, a scrubbing module, and a computerized operation and control module. Each is portable in the sense that it can be moved from place to place in the Tritium Facility and reconnected to the other modules for tritium gas recovery, analysis, decontamination, and cleanup. Mike Benapfl (left) and Vern Switzer arc pictured working at the computerized operation and control module, which permits semi-automatic remote activation of the other three system modules. In the foreground is the gas analysis module where the gas species (tritium as well as other gases) are identified at subatmospheric pressure and routed by the computer module operators to the correct location within the processing system for appropriate treatment and containment. The PTPS has been designed and built to the most stringent standards of worker and environmental protection. About the Journal States Department of Energy, was established in 1952 to do research on nuclear weapons and magnetic fusion energy. Since then, in response to new national needs, we have added other major programs, including laser science (fusion, isotope separation, materials processing), biology and biotechnology, environmental research and remediation, arms control and nonproliferation, advanced defense technology, applied energy technology, and industrial partnerships. These programs, in turn, require research in basic scientific disciplines, including chemistry and materials science, computing science and technology, engineering, and physics. The Laboratory also carries out a variety of projects for other federal agencies. Energy and Technology Review is published monthly to report on unclassified work in all our programs. Please address any correspondence concerning Energy and Technology Review (including name and address changes) to Mail Stop L-3, We have miniaturized current tritium processing technology for removing tritium from facilities and decontaminating them and have packaged the technology in modular units that are self-contained, easily transportable, and usable in confined spaces. X-Ray Lasers and High-Density Plasma We are developing the laboratory x-ray laser as a probe to obtain high-resolution images of high-density plasmas produced at the Nova laser facility. Three techniques and future applications are described. Research Highlights Silicon Carbide Microcomponents Modern Technology for Advanced Military Training Abstracts h b STE DlETRlBUTlON Of THIS DOCUMENT IS UNLIMITED U 1 9 20 22 25

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