book: Inclusion of cool roofs in nonresidential Title 24 prescriptive requirements [An article...

book: Inclusion of cool roofs in nonresidential Title 24 prescriptive requirements [An article from: Energy Policy] | R. Levinson, H. Akbari, ...

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Inclusion of cool ...

	Inclusion of cool roofs in nonresidential Title 24 prescriptive requirements [An article from: Energy Policy] R. Levinson, H. Akbari, ... Elsevier, 2005 view larger image
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This digital document is a journal article from Energy Policy, published by Elsevier in 2005. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Roofs that have high solar reflectance (high ability to reflect sunlight) and high thermal emittance (high ability to radiate heat) tend to stay cool in the sun. The same is true of low-emittance roofs with exceptionally high solar reflectance. Substituting a cool roof for a non-cool roof tends to decrease cooling electricity use, cooling power demand, and cooling-equipment capacity requirements, while slightly increasing heating energy consumption. Cool roofs can also lower citywide ambient air temperature in summer, slowing ozone formation and increasing human comfort. DOE-2.1E building energy simulations indicate that use of a cool roofing material on a prototypical California nonresidential (NR) building with a low-sloped roof yields average annual cooling energy savings of approximately 3.2kWh/m^2 (300kWh/1000ft^2), average annual natural gas deficits of 5.6MJ/m^2 (4.9therm/1000ft^2), average annual source energy savings of 30MJ/m^2 (2.6MBTU/1000ft^2), and average peak power demand savings of 2.1W/m^2 (0.19kW/1000ft^2). The 15-year net present value (NPV) of energy savings averages $4.90/m^2 ($450/1000ft^2) with time-dependent valuation (TDV), and $4.00/m^2 ($370/1000ft^2) without TDV. When cost savings from downsizing cooling equipment are included, the average total savings (15-year NPV+equipment savings) rises to $5.90/m^2 ($550/1000ft^2) with TDV, and to $5.00/m^2 ($470/1000ft^2) without TDV. Total savings range from 1.90 to 8.30$/m^2 (0.18-0.77$/ft^2) with TDV, and from 1.70 to 7.10$/m^2 (0.16-0.66$/ft^2) without TDV, across California's 16 climate zones. The typical cost premium for a cool roof is 0.00-2.20$/m^2 (0.00-0.20$/ft^2). Cool roofs with premiums up to $2.20/m^2 ($0.20/ft^2) are expected to be cost effective in climate zones 2-16; those with premiums not exceeding $1.90/m^2 ($0.18/ft^2) are expected to be also cost effective in climate zone 1. Hence, this study recommends that the year-2005 California building energy efficiency code (Title 24, Part 6 of the California Code of Regulations) for NR buildings with low-sloped roofs include a cool-roof prescriptive requirement in all California climate zones. Buildings with roofs that do not meet prescriptive requirements may comply with the code via an ''overall-envelope'' approach (non-metal roofs only), or via a performance approach (all roof types).

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nonresidential