Energy-Efficient Landscaping

What is Energy-Efficient Landscaping?

Energy-efficient landscaping refers to the selection and placement of trees, shrubs, and vegetation that help reduce a building’s energy use. Heating, cooling, and ventilation comprise over half of the commercial buildings’ energy consumption.[1] Energy-efficient landscaping provides a low-cost solution to reducing energy use with both economic and environmental benefits.

Heat exchange occurs through air infiltration[2] conduction[3] and solar-radiation.[4] Energy-efficient landscaping uses four main strategies to moderate these processes.

1. Plant trees and shrubs to provide shade and reduce solar heat gain in the summer.
2. Plant trees and shrubs to prevent heat loss in the winter.
3. Plant trees and shrubs to deflect winter winds and maintain a warmer microclimate around the building.
4. Consider a vegetated roof to provide extra thermal mass and insulation.

How to Implement Energy-Efficient Landscaping

When designing an energy-efficient landscape consider New Jersey’s temperate climate and your property’s unique micro-climate. Before construction begins, consult with an International Society for Arboriculture (ISA) certified arborist who can work with the project team to formulate a plan to protect existing trees (see Tree Protection and Placement). When possible, protect or enhance the diversity of native species and age of trees on the site and maintain them as necessary (see Native and Adapted Plants). Resources such as Jersey-Friendly Yards offer plant information and an easily searchable plant database.

Tips and Maintenance

• Consider mapping the sun’s path to understand the site’s microclimate better.
• Create a landscape and maintenance plan.
• Do not plant trees too close to the building because roots may grow into the foundation. Place medium to large trees at least 20 feet from the building. Place trees that result in small, full-grown crowns closer to the building to maintain both energy and aesthetic value. See the Arbor Day Tree Guide for growth rate and crown size information for specific tree species.
• Review the Native and Adaptive Plants strategy for plant selection guidance. Consider genetic diversity to minimize potential disease and insect problems.
• Consider using temporary measures to provide shade until trees reach maturity. For instance, vines growing on a trellis can shade air conditioning units. If using mature trees for shading or a windbreak, plant a temporary row of faster-growing shrubs upwind of the permanent row and remove before the roots interfere with the permanent planting.

Figure 1- Strategic Tree Placement (Source: Minnesota Department of Commerce Energy Information Center)

Benefits

• According to a Lawrence Berkeley National Labs study, landscapes that provide shade resulting in temperatures 3-6°F cooler can decrease the energy load required for buildings by 9-20%.
• Shading an air conditioning unit can increase its efficiency by up to 10% and allow units to operate more efficiently.[5]
• Windbreaks can save up to 25% on heating costs by protecting the microclimate surrounding your building.[6]
• Proper landscaping decreases energy demand to heat and cool buildings, thus reducing carbon dioxide emissions.

Costs

Moderate upfront investments in energy-efficient landscaping can realize paybacks in as little as eight years as trees and shrubs reach full maturity, offering maximum energy-saving benefits. [7]  Large, deep-rooted deciduous trees provide optimal shading benefits but depending on growth rate of the species, may take up to 5 or 10 years to reach full maturity.

Resiliency

Energy efficient landscaping offers a strong line of natural defense for buildings and the surrounding community.  Instead of implementing costly, time-consuming engineering projects, natural systems such as trees for windbreaks or shade, and wetlands for storm barriers offer protection from the elements, along with substantial energy savings. In the event of a significant heat wave, shade-providing trees help to reduce the urban heat island effect, reduce indoor cooling loads, and reduce stress on the power grid. When emergency events disrupt regular supply and delivery networks, fruit producing trees can supplement local food supplies. Furthermore, properly sited and maintained trees can block buildings from severe winds and offer protection from extreme cold.

Note that debris from storm-related tree damage and downed electric lines caused by wind, snow, and ice, flooding and lightning result in one of the most substantial storm-related expenses. Maintaining tree health through proper pruning, watering, and disease control can help prevent tree damage and preserve the many benefits of trees.

[1] US EIA. 2003.  Commercial Building Energy Consumption Survey, Table E1A. https://www.eia.gov/consumption/commercial/data/2003/pdf/e1a-e11a.pdf  (accessed March 22, 2018).

[2] Air infiltration occurs when outside air enters a house uncontrollably through cracks and openings. https://www.energy.gov/energysaver/weatherize/air-sealing-your-home (accessed April 10, 2018).

[3] Conduction is heat traveling through a solid material https://www.energy.gov/energysaver/principles-heating-and-cooling  (accessed April 10, 2018)

[4] Solar radiation is heat created from sunlight https://www.energy.gov/eere/solar/articles/solar-radiation-basics  (accessed April 10, 2018).

[5] Connecticut State Department of Consumer Protection.  “How to Save on Air Conditioning.” http://www.portal.ct.gov/DCP/Common-Elements/Common-Elements/How-to-Save-on-Air-Conditioning  (accessed March 22, 2018).

[6] Walker, L. and Newman, S.  Landscaping for Energy Conservation.  Colorado State University Extension Publications. no.7.225. March 2009.  http://extension.colostate.edu/docs/pubs/garden/07225.pdf (accessed  March 22, 2018).

[7] US DOE. Landscaping for Shade. https://www.energy.gov/energysaver/landscaping-energy-efficient-homes/landscaping-shade (April 10, 2018).