Over the last five issues of New Life Journal's Green Roots, I, along with other cohorts at Equinox Environmental, have written about some of the fundamental concepts of sustainable landscapes. In the final installment of this series, I want to address how plants and other landscape features can be used to modify indoor temperatures in our homes and buildings.
Designing a landscape with energy efficiency in mind means thinking of the seasons--the cold winter months and the warm summer months in particular. Energy conscious landscape design can reduce heating and cooling costs and help create comfortable environments that are buffered against harsh weather. But before starting to design the landscape, determining the existing conditions is a prerequisite. Solar heat gain, wind speed and direction are affected by landform and topography and can vary from location to location. A site analysis will help determine how effective designing the landscape will be for solar orientation, screening or accessing the sun, and blocking or harnessing the wind.
Remember: the sun heats for free. A southern orientation allows low-angle winter sunlight to enter a building in the winter and maximizes southern exposure for clay lighting and solar access during the rest of the year. For maximizing the benefits of natural solar heat gain, the longest face of a building should face south and have plenty of windows to let in the sunlight.
Trees are terrific for blocking the sunlight or allowing it to pass on through. When building, you can take advantage of shade from existing trees, or you can plant large deciduous trees 15-25 feet away from the south and west facing sides of an existing building. During winter, the sun can reach far inside a building because of its low angle. Deciduous trees, which are leafless in winter, can allow as much as 50 percent of the sun's rays through to provide heat During the summer, up to 96 percent of the sun's direct rays can be blocked by deciduous trees planted around the south and westsides of a building. Shading the roof of a structure from the summer sun can reduce indoor temperatures by as much as lo degrees. Keep in mind, however, that if solar panels are being used it's important not to block solar access to the photovoltaic system. Even though newly planted trees take time to grow, and may take years before they can shade the roof of a house, they will shade the sides of a buliding, which is also beneficial. Also, by...