Streamlined energy-savings calculations for heat-island reduction strategies

<p>We have developed summary tables (sorted by heating- and cooling-degree-days) to estimate the potential of Heat-Island Reduction (HIR) strategies (i.e., solar-reflective roofs, shade trees, reflective pavements, and urban vegetation) to reduce cooling-energy use in buildings. The tables provide estimates of savings for both direct effect (reducing heat gain through the building shell) and indirect effect (reducing the ambient air temperature).</p><p>In this analysis, we considered three building types that offer the most savings potential: residences, offices, and retail stores. Each building type was characterized in detail by Pre-1980 (old) or 1980+ (new) construction vintage and with natural gas or electricity as heating fuel. We defined prototypical-building characteristics for each building type and simulated the effects of HIR strategies on building cooling and heating energy use and peak power demand using the DOE-2.1E model and weather data for about 240 locations in the U.S. A statistical analysis of previously completed simulations for five cities was used to estimate the indirect savings. Our simulations included the effect of (1) solar-reflective roofing material on building [direct effect], (2) placement of deciduous shade trees near south and west walls of building [direct effect], and (3) ambient cooling achieved by urban reforestation and reflective building surfaces and pavements [indirect effect].</p><p>Upon completion of estimating the direct and indirect energy savings for all the selected locations, we integrated the results in tables arranged by heating- and cooling-degree-days. We considered 15 bins for heating-degreedays, and 11 bins for cooling-degree-days. Energy use and savings are presented per 1000 ft² of roof area. In residences heated with gas and in climates with greater than 1000 cooling-degreedays, the annual electricity savings in Pre-1980 stock ranged from 650 to 1300 kWh/1000ft²; for 1980+ stock savings ranged 300 to 600 kWh/1000 ft². For residences heated with electricity, the savings ranged from 350 to 1300 kWh/1000ft² for Pre-1980 stock and 190-600 kWh/1000ft² for 1980+ stocks. In climates with less than 1000 cooling-degree-days, the electricity savings were not significantly higher than winter heating penalties. For gas-heated office buildings, simulations indicated electricity savings in the range of 1100-1500 kWh/1000ft² and 360-700 kWh/1000ft², for Pre-1980 and 1980+ stocks, respectively. For electrically heated office buildings, simulations indicated electricity savings in the range of 700-1400 kWh/1000ft² and 100-700 kWh/1000ft², for Pre-1980 and 1980+ stocks, respectively. Similarly, for gas-heated retail store buildings, simulations indicated electricity savings in the range of 1300-1700 kWh/1000ft² and 370-750 kWh/1000ft², for Pre-1980 and 1980+ stocks, respectively. For electrically heated retail store buildings, simulations indicated electricity savings in the range of 1200-1700 kWh/1000ft² and 250-750 kWh/1000ft², for Pre-1980 and 1980 + stocks, respectively.</p>