Trees Can Save You Energy 12 Months a Year

Robin Stanley

UCCE/El Dorado Master Gardener

Now that the days are getting shorter and we’ve had our first rain of the season, complete with quite an amazing lightning show, it may seem funny to think about the importance of trees in saving energy. Most of us think about trees for their cooling benefits more than for winter insulation and warming. But since experts are predicting that energy costs may skyrocket this fall and winter, it’s good to think about how the selection and siting of landscape trees can save you dollars in both hot and cold weather. And since fall is a great time to plant landscape trees, the choices you make in the next few months can help you reduce your year round energy costs.

According to the website for the California Energy Commission (CEC), http://www.consumerenergycenter.org/homeandwork/homes/outside/landscaping.html, there are a lot of ways trees and other landscape plants can save you energy. Whether you want deciduous or evergreen trees, experts can help you make informed decisions.

You are probably well aware that deciduous trees, those that lose their leaves in the winter, can provide a lot of cooling in the summer. But you may be surprised that the CEC advises that for our climate, you should plant deciduous trees “on the northeast-to-southeast and northwest-to-southwest sides of your house” where “…they can provide excellent protection from the summer sun by shading roof, walls and windows.” By not planting directly on the south side of your house, you allow the suns rays to warm your house in winter, since even the bare branches of these trees can filter the sun more than is desireable in cold weather.

Consider the ultimate size of various trees before deciding what trees to buy and where to plant them. Things like height and branch spread will affect the suitability of a tree for your site, both in winter and summer. The CEC suggests wide spreading trees for the west side of your house, since the sun can beat in west windows all summer, but is too low in the sky to provide much warming in winter months. Depending on the orientation of your house, and windows, and whether you have overhangs, you might want to orient your trees a little to the southwest of windows, so you can preserve the view.

The growth rate of various trees is also an important consideration in making your selection. What seems the most perfect tree might not be if it takes 30 years to reach maturity. So what about evergreens – is there a place for them in your energy-efficient landscape? In winter, they are most useful on the north side of your house, to shelter it from the chilly winter winds. Planted in the right location, as windbreaks, you’ll be glad they keep their insulating needles or leaves all winter.

If you live in a conifer forest, such as Camino and Pollock Pines, you probably have more evergreens than you know what to do with. You may be thinking more in terms of thinning and trimming trees (for fire safety and aesthetics) than you are of adding them. The good news is that this thinning, especially on the east and west sides of your property away from your house, can have the additional benefit in the summer of opening up your property to cooling breezes.