Trees offer many functional and aesthetic benefits, but one of the most common is shade. Because of this, one of the most important aspects of tree selection and planting is placement. Improper placement of trees can diminish the value of the tree on the site. The tree can actually become a liability if it conflicts with infrastructure or just does not providing any useful function at all. It’s important to consider and energy efficient design to obtain shade where it’s needed most such as south or west facing structures.
In this hemisphere, the sun is in the south and the source of cold weather is in the north. Whenever possible, place openings for sunlight and radiant heat primarily on the southern exposure, then on the west and east. For energy efficiency in winter, use the low arc of the sun to capture the maximum amount of warmth through east-, west-, and south-facing windows. Windows with a northern exposure are a source of cool air from prevailing winds during the hot months. So, give the north minimum exposure and maximum natural protection in the winter.
When selecting trees for energy efficiency, don’t plant evergreen trees near the house on southern exposures. Trees may provide some shade and screening but will also block out the warming effects of the sun during winter months. When choosing trees for shade and solar gain, choose larger, deciduous-canopy trees, which provide an advantage year-round. This means shade in the summer, blocking the sun’s energy. In the winter, after leaves have dropped, the sun’s energy can pass through the tree and into the window.
Select good quality trees from a reputable source that are suitable for your location. The old adage, “you get what you pay for” goes for nursery stock as well. Correct placement is critical for an energy-efficient design and reduced maintenance as the tree grows and matures. Be certain the mature height and spread fit the location before purchase and planting the tree. This allows the tree freedom to spread into the design space naturally without excessive pruning needed to prevent conflicts with the home. However, the tree still must be close enough to the house for the canopy to provide shade. A good rule of thumb to begin placing the tree at least 20 feet from the house. For larger shade trees, you may need to plant as far as 40 feet from the house to insure room for growth (Figure 1).
Trees provide many benefits besides shade which includes cleaner air and increased property values. These ecosystem services are the reason why we plant trees, besides beautifying our landscape.
The functional benefits of shading help make homes energy-efficient by creating a cooling effect during the hot summer months and by allowing passive solar gain during cold winter months. However, proper selection and placement is critical to make the tree work for your site. Choose wisely, plant properly.
For more information on tree selection see publication FNR-531-W as well as the video that goes along with the publication, FNR-538-WV. Tips on tree installation can be found in the publication FNR-433-W along with the video FNR-540-WV.