4 0 obj Since only 43% of light occurs in the visible light spectrum, reflectance can be improved without affecting color by increasing the reflectance of UV and IR light. Buildings may earn a rating of between one and four globes. F (50 deg. A value of 0 indicates that the surface absorbs all solar radiation, and a value of 1 (or 100%) represents total reflectivity. It is expressed either as a decimal fraction or a percentage. x��[_oܸ7� �"+�I�h`��؇�6�����ֶl��nr�/��P�$j�{)�^�pH�g~3C�]y���b�_�>6wɯg�ۧ�ή_���/ˇv�ܷ���y���"y}zrvER$���'$��?�Ty&(M*A��N�ק'y� )�Z%;����ɯ�$�-�����RrN�����&���Y`����v=�`��4c %Y���,�NOj���9��`D!�d��,��C�>��M�|�&�PC˘B��L(���%E���rF���sX���f�%s.�.2���^�=9������!��ξi�6�,���`r"��*���H��"ɏ����!g����d�l�����bR�g�L�5����?�|v�"�H�9�dv ��>].R:�N �4�4�s�wj%��,/�W�۾�W�AYKʤ�|k9���sszr��!cB:*��gUwJFlݝ�M��J���ӣ伕r\-�� Initial Solar Reflectance: If you selected “no”to box 1, input the CRRC listed Initial Solar Reflectance value as a decimal between 0 and 1. It is therefore best to estimate energy savings based on weathered solar reflectance values rather than clean roof values. H��U[O�0~ϯ�c���˄�F��6hB���[۰���_?�NᄴE�Η�ܾsl���w�U������� ��0�(��������V ��#�v)ʐ�UE�-�*��Tp)Q����6�!��Z��. The findings concluded that the temperatures above cool roofs were higher than those of a darker colored roof material. [32] To satisfy the consumer demands for darker colors which still reflect significant amounts of sunlight, different materials, coating processes, and pigments are used. [31], Cool roofs fall into one of three categories: roofs made from cool roofing materials, roofs made of materials that have been coated with a solar reflective coating, or green roofs. The program does not, however, specify minimum requirements for solar reflectance or thermal emittance. It reports the net annual energy savings (cooling energy savings minus heating penalties) and thus is only applicable to the buildings with a heating and/or cooling system. Major Fuel Consumption by End Use for All Buildings, 2003", "Measured energy savings and demand reduction from a reflective roof membrane on a large retail store in Austin", "DOE Takes Steps to Implement Cool Roofs across the Federal Government", http://energy.gov/eere/femp/articles/new-and-underutilized-technology-cool-roofs, "All Certified Products - ENERGY STAR Qualified Products", "USGBC - Southern California Edison - Wildomar", "Southern California Edison's New Service Center in Wildomar Awarded Platinum Certification by National Building Council", "White Trumps Black in Urban Cool Contest", "Cool Roofs Planned Across CUNY's Rooftops", https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120009506_2012009395.pdf, "Bright Is The New Black: New York Roofs Go Cool", "Op-Ed: White Roofs Are the White Knight We Need to Slay Climate Change", "So Cool! [30], This tool was the collaboration of both Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory in order to provide industry-consensus roof savings for both residential and commercial buildings. A perfect SRI is approximately 122, the value for a perfect mirror, which absorbs no sunlight and has very low emissivity. “This measure is likely more cost-effective in the hot and humid climate zone, which has a long cooling season, than in the very cold climate zone, for example. SRI (Solar Reflectance Index) SRI is a value that incorporates both solar reflectance and emittance in a single value to represent a material's temperature in the sun. It may be useful in construction materials to keep roofs and walls cool. The Green Globe system is used in Canada and the United States. �T�A$D���ak�b3�qzBJa@��P `��\ o�n�3�ebZ�`�¢��@jCJ{�1^�=Gt�V0���ҒAt/?� �b�ߝ��A��{� _;E� When sunlight falls on a white roof much of it is reflected and passes back through the atmosphere into space. h�bbd``b`�S�S�����X�@�c?��$8��I&F�� �H��3� � � Table 2 shows the visible transmittance, visible reflectance, solar transmittance, solar reflectance, and normal emittance of each calculated sample. TARGET VAlUES . Though a more reflective roof can lead to higher heating costs in the colder months, studies have shown that the increased winter heating costs are still lower than the summer cooling cost savings. 832 0 obj <> endobj <>/ExtGState<>/XObject<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.32 841.92] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>>

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