William A Miller

Weathering of Roofing Materials-An Overview

Deliverable for CEC Task 2.6.4. Report LBNL-59724. Submitted to Construction and Building Materials, February, 2006 Weathering of Roofing Materials-An Overview Paul Berdahl, Hashem Akbari, and Ronnen Levinson Lawrence Berkeley National Laboratory Berkeley, CA 94720 and William A. Miller Oak Ridge National Laboratory Oak Ridge, TN 37831 Abstract An overview of several aspects of the weathering of roofing materials is presented. Degradation of materials initiated by ultraviolet radiation is discussed for plastics used in roofing, as well as wood and asphalt. Elevated temperatures accelerate many deleterious chemical reactions and hasten diffusion of material components. Effects of moisture include decay of wood, acceleration of corrosion of metals, staining of clay, and freeze- thaw damage. Soiling of roofing materials causes objectionable stains and reduces the solar reflectance of reflective materials. (Soiling of non-reflective materials can also increase solar reflectance.) Soiling can be attributed to biological growth (e.g., cyanobacteria, fungi, algae), deposits of organic and mineral particles, and to the accumulation of flyash, hydrocarbons and soot from combustion. 1. Introduction Roofing materials are exposed to the elements, namely wind, sunlight, rain, hail, snow, atmospheric pollution, and temperature variations and consequently degrade over time. Even the most durable materials are modified by deposition of ambient dust and debris, and may provide an opportunity for colonization by biological organisms such as cyanobacteria, fungi and algae. In this paper, we broadly review how weathering occurs and discuss several engineering strategies that are employed for improving the performance of roofing materials. We have been engaged in a multi-year project to develop and commercialize cooler, solar-reflective roofing in conjunction with a number of industrial partners. These materials can save energy used for air conditioning and improve occupant comfort. Since reflective white materials are sometimes not suitable from an architectural standpoint, the work has included materials with specified visual colors but with high near-infrared reflectance [1]. This paper is a summary of what we have learned concerning the weathering of roofing materials.

The Correlation of Simultaneous Heat and Mass Transfer Experimental Data for Aqueous Lithium Bromide Vertical Falling Film Absorption

A study of simultaneous heat and mass transfer was conducted on a vertical falling film absorber to better understand the mechanisms driving the heat and mass transfer processes. Thermographic phosphors were successfully used to measure the temperature profile along the length of the absorber test tube. These measures of the local variations in temperature enabled calculation of the bulk concentration along the length of the absorber. The bulk concentration varied linearly, which infers that the concentration gradient in the direction of flow is approximately constant. The implication is that the mass flux and therefore the absorber load can be solved for using a constant flux approximation. Design data and correlations are sparse in the open literature. Some experimental data are available; however, all literature data to date have been derived at mass fractions of lithium bromide ranging from 0.30 to 0.60. Experiments were therefore conducted with no heat and mass transfer additive on an internally cooled smooth tube of 0.01905-m outside diameter and of 1.53-m length. The data, for testing at 0.62 and 0.64 mass fraction, were scaled and correlated into both Nu and Sh formulations. The average absolute error in the Nu correlation is about ±3.5% of the Nu number reduced from the experimental data. The Sh correlation is about ±5% of the reduced Sh data. Data from the open literature were reduced to the authors Nu and Sh formulations, and were within 5% of the correlations developed in the present study. The study therefore provides test data with no heat and mass transfer additive and correlations for the coupled heat- and mass-transfer process that are validated against the extensive experimental data.

BUILDING-INTEGRATED PHOTOVOLTAICS FOR LOW-SLOPE COMMERCIAL ROOFS

A photovoltaic (PV) distributed energy resource (DER) was established to support the Tennessee Valley Authority’s Green Power Switch program, which allows utility customers to purchase blocks of electricity generated by solar resources. The PV DER was also used to study the potential shading benefits of roof-mounted PV systems for commercial buildings. Test data derived by monitoring an offset-mounted PV array shading a built-up low-slope roof system shows that the annual savings per square foot of low-slope roof can be as high as

A Comparison of Simulation Capabilities for Ducts

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In-Depth Analysis of Simulation Engine Codes for Comparison with DOE s Roof Savings Calculator and Measured Data

1.95 per square meter) in Phoenix, AZ.

Final review of the Campbell Creek demonstrations showcased by Tennessee Valley Authority

Reports produced before January 1, 1996, may be purchased by members of the public from the following source. Reports are available to DOE employees, DOE contractors, Energy Technology Data Exchange (ETDE) representatives, and International Nuclear Information System (INIS) representatives from the following source. Government nor any agency thereof, nor any of their employees, 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. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Figure 1. Comparison of energy impacts of 4% leaky ducts in an attic with a sealed floor versus 10%, and 20% leaky ducts in attic space without a sealed floor,. ABSTRACT Typically, the cheapest way to install a central air conditioning system in residential buildings is to place the ductwork in the attic. Energy losses due to duct-attic interactions can be great, but current whole-house models are unable to capture the dynamic multi-mode physics of the interactions. The building industry is notoriously fragmented and unable to devote adequate research resources to solve this problem. Builders are going to continue to put ducts in the attic because floor space is too expensive to closet them within living space, and there are both construction and aesthetic issues with other approaches such as dropped ceilings. Thus, there is a substantial need to publicly document duct losses and the cost of energy used by ducts in attics so that practitioners, builders, homeowners and state and federal code officials can make informed decisions leading to changes in new construction and additional retrofit actions. Thus, the goal of this study is to conduct a comparison of AtticSim and EnergyPlus simulation algorithms to identify specific features for potential inclusion in EnergyPlus that would allow higher-fidelity modeling of HVAC operation and duct transport of conditioned air. It is anticipated that the resulting analysis from these simulation tools will inform energy decisions relating to the role of ducts in future building energy codes and standards.

Building-Integrated Photovoltaics for Low-Slope Commercial Roofs

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Methods of creating solar-reflective nonwhite surfaces and their application to residential roofing materials

Reports produced before January 1, 1996, may be purchased by members of the public from the following source: Government nor any agency thereof, nor any of their employees, 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. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Fig. 7. Resistance heat use in the builders home (CC1) with the original single-speed heat pumps and also with the Carrier Greenspeed™ variable-speed air-source heat pumps. Data is from the same time periods shown in Fig. vii ACRONYMS ACH air exchange rate ccSPF closed cell spray polyurethane foam insulation DHW domestic hot water Dish W dish washer ECM electrically commutated motor EF energy factor EPRI Electric Power Research Institute HERS home energy rating score HP heat pump HPWH heat pump water heater HSPF heating seasonal performance factor LF load factor NFRC National Fenestration Rating Council ocSPF open cell spray polyurethane foam insulation OSB oriented strand board Plugs electrical plug loads RESNET® Residential Energy Services Network SEER seasonal energy efficiency ratio SHR sensible heat ratio SHW solar hot water TV television Wash washer WH water heater XPS extruded polystyrene insulation ix ACKNOWLEDGMENTS

Field thermal performance of naturally ventilated solar roof with PCM heat sink

A photovoltaic (PV) distributed energy resource (DER) was established to support the Tennessee Valley Authority’s Green Power Switch program, which allows utility customers to purchase blocks of electricity generated by solar resources. The PV DER was also used to study the potential shading benefits of roof-mounted PV systems for commercial buildings. Test data derived by monitoring an offset-mounted PV array shading a built-up low-slope roof system shows that the annual savings per square foot of low-slope roof can be as high as

Understanding the long-term effects of environmental exposure on roof reflectance in California

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