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Description:
A roof with high solar reflectance and high thermal emittance (e.g., a white roof) stays cool in the sun, reducing cooling power demand in a conditioned building and increasing summertime comfort in an unconditioned building. The high initial solar reflectance of a white membrane roof (circa 0.8) can be lowered by deposition of soot, dust, and/or biomass (e.g., fungi or algae) to about 0.6; degraded solar reflectances range from 0.3 to 0.8, depending on exposure. We investigate the effects of soiling and cleaning on the solar spectral reflectances and solar absorptances of 15 initially white or light-gray polyvinyl chloride membrane samples taken from roofs across the United States. Black carbon and organic carbon were the two identifiable strongly absorbing contaminants on the membranes. Wiping was effective at removing black carbon, and less so at removing organic carbon. Rinsing and/or washing removed nearly all of the remaining soil layer, with the exception of (a) thin layers of organic carbon and (b) isolated dark spots of biomass. Bleach was required to clear these last two features. At the most soiled location on each membrane, the ratio of solar reflectance to unsoiled solar reflectance (a measure of cleanliness) ranged from 0.41 to 0.89 for the soiled samples; 0.53 to 0.95 for the wiped samples; 0.74 to 0.98 for the rinsed samples; 0.79 to 1.00 for the washed samples; and 0.94 to 1.02 for the bleached samples. However, the influences of membrane soiling and cleaning on roof heat gain are better gauged by fractional variations in solar absorptance. Solar absorptance ratios (indicating solar heat gain relative to that of an unsoiled membrane) ranged from 1.4 to 3.5 for the soiled samples; 1.1 to 3.1 for the wiped samples; 1.0 to 2.0 for the rinsed samples; 1.0 to 1.9 for the washed samples; and 0.9 to 1.3 for the bleached samples.

This digital document is an article from Wood & Wood Products, published by Vance Publishing Corp. on January 1, 2005. The length of the article is 899 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

Citation Details
Title: Light-colored Koto has wide range of uses and names.(Wood of the month: Koto)
Author: Jo-Ann Kaiser
Publication: Wood & Wood Products (Magazine/Journal)
Date: January 1, 2005
Publisher: Vance Publishing Corp.
Volume: 110 Issue: 1 Page: 41(2)

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This digital document is an article from Wood & Wood Products, published by Vance Publishing Corp. on November 1, 1995. The length of the article is 1032 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.

From the supplier: Limba is a tree that is native to West Africa. The color of its wood ranges from pale yellow to straw-colored while its heartwood has streaks that range from grey to black. Limba is most often used for interior joinery, shop fittings, furniture, desks and coffins. It is also a popular choice for decorative veneers.

Citation Details
Title: Limba: the light-colored West African wood.
Publication: Wood & Wood Products (Magazine/Journal)
Date: November 1, 1995
Publisher: Vance Publishing Corp.
Volume: v100 Issue: n12 Page: p52(1)

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