Can Large Canopy Trees Lower Summer Cooling Costs?
Benefits of a Large Tree Canopy
Staying Cool in the City
When we hear about building green infrastructure, it’s often related to new parks or rain gardens, but planting large canopy trees in your neighborhood can also make a significant contribution to the environment. The shade from strategically placed trees can lower summertime energy costs and provide a substantial return over many years from a modest one-time investment.
Shading just 17% of your home with a tree can result in a savings of $10 a month on cooling costs, according to an article co-authored by Beau Brodbeck of Auburn University and Sharon Jean-Philippe of the University of Tennessee. Shading 50% of your house can save an additional $20 per month.
A maple tree provides dense shade because of large leaves that effectively filter the sun.
How soon after planting can a tree affect your cooling costs? Brodbeck and Jean-Philippe cite one study that estimates homeowners can realize a 3% energy savings within 5 years of planting a tree, and after 15 years, when a tree is at mature height, the savings on cooling costs can increase to 12%. Another study they reference shows that the net cooling effect of a young, healthy tree could be equivalent to up to 10 room-size air conditioners running for 20 hours a day! Achieving these savings is as easy as planting the right tree in the right place.
How Do Trees Lower Temperatures?
Trees cast shade when their leaves block, absorb and reflect sunlight. The ground beneath trees tends to be cooler because the soil, stabilized by the trees’ root systems, holds more water and doesn’t dry out as quickly. Evaporation from the ground cools the air, as does transpiration from the trees as they pull water from the soil through their roots and trunks, releasing the moisture from their leaves. The temperature under a tree can be up to 25 degrees cooler than the ambient temperature in the surrounding area!
When radiant energy from the sun heats home surfaces like walls, roofs and windows, air conditioners have to work harder. “Planting trees to shade the air conditioner unit can also conserve energy,” according to Brodbeck and Jean-Philippe, by keeping units from overheating. Placing trees in specific places in the yard and in relation to the house is an important way to make sure shade is being cast in the most effective way.
Trees planted near your home can significantly reduce your summer cooling costs.
Strategic Shade-Scaping
When planning to plant trees for shade, the task must be approached strategically. Information about the long-term growth of the tree needs to go into placement decisions before anything is planted.
A large-canopy tree should be placed where it will cast shade onto the house when it reaches mature height, without being near enough to pose a threat to property or people in case of damage to the tree. The height and placement is also important so that trees won’t interfere with utility lines. Shorter understory trees and shrubs can be planted below them, but large-canopy trees should be kept at a distance and trimmed and maintained by a certified arborist.
Consider the shape and density of the tree when you choose one. How tall will it be at maturity? How wide will the canopy spread? Annual leaf cycles should also influence the choice. Deciduous trees lose their leaves in the winter, providing shade in the summer and allowing the sun’s warmth to pass through their bare branches in the cooler months. Evergreens, on the other hand, provide shade year-round. The type of tree species chosen becomes both an aesthetic and functional decision, since the height and seasonal leaf cover will determine how effective it will be at cooling the house.
Planting shade trees requires homeowners to take a look at the whole yard’s landscaping, since the safety and height requirements vary depending on the size and features of a property. Making use of vertical space is an important aspect of home energy management through landscaping. Hedges can shade windows that experience direct sunlight, both cooling and giving privacy benefits.
Trees and plants of all kinds across your yard will contribute to keeping the surrounding temperatures a little cooler than they would be otherwise. According to the EPA, a well-planned landscape can reduce an unshaded home’s air conditioning costs by 15 to 50 percent.
Urban Cooling
Urban heat islands are areas where temperatures are higher from solid, impermeable cover like concrete and asphalt, which absorb and radiate heat. This happens especially when there is a lack of trees and vegetation to shade the ground. It’s important for homeowners to maintain yards with abundant green cover since most urban green space is located on private property.
For businesses and communities, green roofs and planting along sidewalks, streets and parking lots can contribute to neighborhood shading. Keeping the surrounding environment cool helps keep the area more comfortable, and neighborhoods with sufficient canopy and green cover can be up to 6 degrees cooler than neighborhoods without. Trees are a structural investment to stabilize a place against rising temperatures and extreme weather events.
Taking the time to strategically plan plantings in your yard for energy savings gives returns over years while also providing a more ambient and robust local environment. The aesthetic, public health and recreational benefits of trees increase quality of life in the area, as well as increasing property values. Healthy mature trees can be worth several thousand dollars, and well-landscaped properties can increase in appraised value.
Contact us at the Nashville Tree Conservation Corps to get help with identifying and planting the right trees for your shade-related needs. Subscribe to our newsletter to stay up-to-date on tree news and tree care.