SIMULATION OF TREE SHADE IMPACTS ON RESIDENTIAL ENERGY USE FOR SPACE CONDITIONING IN SACRAMENTO

Tree shade reduces summer air conditioning demand and increases winter heating load by intercepting solar energy that would otherwise heat t he shaded structure. We evaluate the magnitude of these effects here f or 254 residential properties participating in a utility sponsored tre e planting program in Sacramento, California. Tree and building charac teristics and typical weather data are used to model hourly shading an d energy used for space conditioning for each building for a period of one year. There were an average of 3.1 program trees per property whi ch reduced annual and peak (8 h average from 1 to 9 p.m. Pacific Dayli ght Time) cooling energy use 153 kWh (7.1%) and 0.08 kW (2.3%) per tre e, respectively. Annual heating load increased 0.85 GJ (0.80 MBtu, 1.9 %) per tree. Changes in cooling load were smaller, but percentage chan ges larger, for newer buildings. Averaged over all homes, annual cooli ng savings of $15.25 per tree were reduced by a heating penalty of $5. 25 per tree, for net savings of $10.00 per tree from shade. We estimat e an annual cooling penalty of $2.80 per tree and heating savings of $ 6.80 per tree from reduced wind speed, for a net savings of $4.00 per tree, and total annual savings of $14.00 per tree ($43.00 per property ). Results are found to be consistent with previous simulations and th e limited measurements available. Published by Elsevier Science Ltd.