Written by Colorado Green NOW

Benefits of trees in the landscape include the value of cooling our environments through shading contributions and evapotranspiration of water. Well-positioned trees in residential landscapes, while offering scale, beauty, and function, can also help save homeowners money on both cooling and heating bills. The U.S. Department of Energy states that “carefully positioned trees can save up to 25% of the energy that a typical household uses.” With energy bills of perpetual concern for homeowners (heating and cooling compromise 50% of a household’s annual energy consumption), consider the value of intention selection and placement of plant material to not only shade the home but maximize available solar access for warming in the winter. Screening and reducing winter wind velocity with windbreaks is an additional option.

When designing a landscape, consultations with the homeowner frequently include topics like the location of decks, patios, screening, and other functional allocations to consider in the design process. Shading those areas of congregation and gathering is important. These discussions are essential but how often does the conversation progress to consider crafting a landscape that helps maximize the energy efficiency of the residence and result in a significant return on investment? Designing for beauty will always be a goal but imagine design layouts that address how to specifically modify the climate around the home by reducing both heat gain in summer and heat loss in winter. Presenting and promoting landscape options that positively affect energy use year-round further results in saving “energy dollars” for the homeowner is a “hard sell”. Decreased energy demands will additionally reduce carbon dioxide emissions related to energy generation. The residential sector currently accounts for approximately 20% of energy-related greenhouse gas emissions directly related to heating and cooling.

On those hot summer days, homeowners naturally seek out shaded respites. The contributions of trees in shaded settings like parks can lower surrounding air temperatures between 9 to 12 degrees. By transpiring water, altering windspeeds, shading surfaces, and modifying the storage and exchange of heat among urban surfaces; trees affect local climate and thereby influence thermal comfort and air quality. When addressing how to positively affect energy use on the micro-scale for clients, these landscape design tips are focused on addressing solar exposure of the structure for heating and cooling as well as modifying winds for maximum energy efficiency.

In the United States, 75% of homes have air conditioners that provide cooling services at the annual expense of $29 billion. With variable weather patterns, concerns about global warming and fluctuating energy costs. With variable weather patterns, concerns about global warming, and fluctuating energy costs, the notion that landscape can help mitigate annual expenses on energy use is something to be shared with clients. It’s estimated that 50% of the unwanted summer heat warming of our homes comes from the sun shining through the windows. In the peak of summer, twice the solar energy comes through the east and west-facing windows as opposed to windows to the south due to high sun angles. Do consider, however, that in those winter months, the winter sun reaching the structure is equally important for helping warm the home and reduce those heating bills. Observe the orientation of the home to identify those windows that would most benefit by summer shading by deciduous trees that will later allow welcome solar energy access after losing foliage in autumn. More energy-efficient windows, overhangs, and other shading strategies will also help lessen some solar inputs in the hotter months.

Roofs, sidewalks, driveways, and other surfaces also absorb light and heat, affecting the microclimate. This is where tree shading benefits are additionally effective. Tree shading is the most cost-effective way to reduce solar heat gain on the structure and cut air conditioning bills. It’s of no surprise that the loss of a large shade tree in proximity to the home results in a significant increase in cooling bills.

The challenge with placing trees in the landscape is not simply about location but considering the site, soils, and other factors that might dictate specific selections. Many of the studies regarding the best sitting for medium to large trees for shading windows and portions of the roof indicate 20-25’ from the structure. Placement closer to a corner (15’) is acceptable and while trees to the south may have ornamental merit, consider low solar angles in winter and the importance of winter sun reaching those windows. As mentioned above, shade provided from even larger trees to the south may have some value on roof shading, but the shadows are cast straight down with peak summer solar angles. Tree benefits increase over time and in the case of shading to the east and west of the structure, having deciduous selections that will extend 10’ and more above the height of the windows will have the most immediate and substantial impact over time. The number one priority placement for energy-efficient contributions from shade is to the west of the structure. Placement to the east is the next priority. The U.S. Department of Energy indicated that the proper placement of three appropriate trees for shading can result in average household savings of $100-$250 annually.

Two considerations for energy savings related to landscaping closer to the home include foundation plants and the air conditioner. Air conditioners, when shaded, can have a 10-40% increase in efficiency which makes sense on the hottest days. Maintaining air circulation around the unit and keeping the area tidy is important but do provide some shade for those units. Foundation plantings are always part of our design process but consider the value of these plantings in providing some insulation along the foundation and buffering those winter winds. Evergreen selections are particularly

effective. Do provide space between plantings and the structure for air circulation and an avenue for maintenance.

Winter weather, while quite variable, can still be brutal on our landscapes, residences, and heating bills. Those deciduous trees placed for summer shading will now allow sunlight to reach the roof and windows of the home to provide some welcome heating. Winter winds buffeting the home and infiltrating the door and window frames become challenging to manage. Home modifications to address proper insulation are common.

A windbreak is a barrier of trees, typically arranged in multiple rows, that redirects and modifies the force of the wind. By absorbing the wind’s energy, a windbreak will deflect the wind to higher elevations and redirect horizontal airflow in random directions. You will see windbreaks extensively in agricultural areas where they serve the purpose of protecting the soil as well. In areas, like Wisconsin and the mid-west tall rows of white pines and Norway spruces in many areas were planted over 50 years ago with the intent of challenging those damaging winter winds. Mature windbreaks can cut winter fuel consumption for heating by an average of 25-40%. In smaller-scale residential landscapes, there is limited space for larger windbreak systems, but hedges and well-placed evergreens will deflect the wind. Cooling summer winds should always be accommodated in any situation so avoid overzealous blockages that create stagnant or limited air flow.

Windbreaks are common to the north and west of structures to address winter wind flow but still allow cooling summer breezes from the southwest. The extent of windbreak protection is proportional to the height of the windbreak which comes with time. The best buffer or protection occurs within the “envelope” of 4 to 5 times the height of the windbreak. Benefits have been measured within 30 times the height of the windbreak but also consider the importance of windbreak density and porosity and how that might fluctuate over time.

While a single row of spruces or pines would be functional, the danger is in the loss of any specimens or the collective decline of a monoculture in time. The loss of lower limbs on older specimens is a concern as well. Multiple rows of evergreens interspersed with deciduous shrubs of varying heights is the most effective combination. Spruces, pines, and firs are common candidates as are arborvitae in areas with minimal animals. Windbreaks typically include a row of shrubs to screen lower gaps but also catch snow. There are many references and manuals that give additional advice on proper windbreak formation. Wider windbreaks can also be managed to be beneficial to wildlife for food and shelter.

Colorado State University recommends these five trees to provide a windbreak:

· Black Hills Spruce

· Norway Spruce

· Vanderwolf’s Pyramid Pine

· Green Giant Arborvitae

· Colorado Blue Spruce

A clients efficient landscape design, while still offering all the contributions of beauty and functionality, provides a low-cost solution to reducing energy consumption and saving money. Energy-efficient landscaping can positively affect the energy performance of residences, and these landscapes will ultimately provide enough energy savings in return for the initial investment. Read more on designing Windbreaks from Colorado State University here.