While living air greenwalls, which we have previously discussed here, can be highly effective at maintaining the interior climate of a building, so too can natural vegetation be employed to increase the energy efficiency of a home. According to Landscape For Life, fully 11% of the total energy usage in the United States is accounted for by heating and cooling. A properly designed and maintained landscape then, where applicable, is no small matter, as it can cut these bills by up to 40% during the most extreme seasons.
The effectiveness of you landscape's impact on energy consumption, as well as the methods employed to achieve the best results, vary greatly by climate region. The United States has four of these distinct regions, each with their own unique conditions. The four zones are classified as cool, temperate, hot and arid, and hot and humid. Here in the Northeast, we are solidly ensconced in the temperate region, yet each zone has its own particular methods for dealing with landscaping.
In cool climates, your aim is to increase energy efficiency in the winter, utilizing available heat to its maximum benefit. To that end, a homeowner in this climate should avoid planting trees on the southern side of a house, thereby preventing sunlight from reaching walls or windows. Tall vegetation should be employed as a windbreak to mitigate winter winds, one of the most effective culprits at driving heating costs. Southern and Western facing walls can be shaded in the summertime, if overheating is a problem. Deciduous plants are particularly good in this arena, allowing low-angle sunlight to pass in the winter.
Temperate climates require much of the same planning, although efforts should be made to determine the prevailing winds for each season. Once established, vegetation can be engineered in such a way that it blocks Winter winds, while simultaneously funneling Summer winds toward a building, fostering ambient cooling. The roof, as well as Eastern and Western facing walls, should be shaded as well, to help mitigate summer cooling costs.
As the average temperature of a climate increases, so it becomes more important to harnessl summer breezes properly. Wind should be deflected away from houses that are air-conditioned, however, and in humid climates, plants that require frequent watering should be kept at a distance from a home, lest they trap humid air nearby.
Shade is a key weapon when it comes to maximizing the energy efficiency of your home. Simply covering an air conditioner can improve the unit's performance by as much as 10%, according to the Department of Energy. Not only should windows be shaded as well, since a building gains much more heat through them than insulated walls, but known heat sinks, like an asphalt-shingled roof, should be carefully managed as well. Dark-colored parts of a structure act as heat sinks, and can radiate significant amounts of heat to surrounding areas, so it is crucial that they are properly shaded in the summer months.
Various types of vegetation are better employed for specific purposes than others. Vines, for instance, grow fast and are highly effective for shading purposes. Though they should be avoided in cooler climates, where heat gain from sunshine is desired in cooler months, shading devices in warmer areas can be made twice as effective through their use.
Tress and shrubs, meanwhile, are not only extremely useful for shading purposes, but also when arranged as a windbreak. Though trees take more time to grow and fill in, temperatures can be as much as 25 degrees cooler under a tree than near an asphalt-paved, open area. Interior temperatures can be mitigated by as much as 8 to 10 degrees by a single, strategically placed tree. By keeping them at least 15 feet away from the building, homeowners can also insure that root systems will do no damage to a foundation. In humid climates, this space will also allow for the free circulation of air around a building.
If planting tress as a windbreak, homeowners should be careful to set them a distance away from the building equal to 2 to 5 times the tree's mature height. The most effective windbreaks protect from multiple directions. A South Dakota study found that a home's fuel consumption can be cut by 40% by windbreaks oriented to the West, East and North sides of a building. Multiple rows can be used to engineer these breaks, and when combined with walls, Earth berms, or fences, trees provide a natural avenue for some air to flow through, allowing the windbreak to function properly.
Careful planning when preparing the landscape around your home can have dramatic, long term effects. While energy efficiency is a constantly moving target, using these examples of properly engineered vegetation will help to not only get you closer to that goal, but also provide all of the other natural aesthetic and climactic benefits that trees have to offer.