If someone were to suggest that there was a simple and inexpensive way to reduce both your summer air conditioning and winter heating bills, while reducing noise pollution and increasing the value of the property, you would probably be skeptical of the claim. Throw in an improvement to air quality and a reduction in storm water pollution and the idea may really seem too good to be true.
Believe it or not, planting trees and shrubs on your property and along public ways provides all the benefits described above with very modest upfront costs.
While there have been many studies confirming that appropriately placed trees and shrubs lead to reduced energy costs, two recent natural disasters here in Massachusetts have provided a living laboratory to study the issue. The first was the Asian Longhorned Beetle infestation in Worcester and surrounding areas of central Massachusetts, where 23,234 trees were cut down in the battle against this invasive menace. Over 20,000 trees in Worcester alone were removed with whole neighborhoods laid bare of shade trees. Secondly, a June 2011 tornado with winds up to 165 mph roared through Springfield, MA leaving entire neighborhoods barren of shade trees.
A study conducted out of UMass Amherst Graduate School estimates that the lack of shade trees in Worcester increased the summer cooling costs by 37%. This finding is within the range of other studies from around the country that estimate anywhere from a 7% to a 47% reduction in energy costs depending on how and where the particular study was conducted because of appropriately place trees and shrubs.
The concept is simple: the shade tree blocks the hot sun from the roof, windows, and outside walls of a house or building. In the summer, a tree can block up to 90% of the suns energy and use it for photosynthesis. A study found that shade trees can reduce the maximum temperature of an outside wall and roof from 20 degrees to 45 degrees. In another study, tree shading was found to reduce the temperatures inside parked cars by 45 degrees compared to those cars parked in the full sun.
So, if you plant trees in the right location on your property, you can expect a noticeable reduction in your AC (cooling) costs during the hot summer months. The trees should be planted on the south, west, or east side of your house and should be deciduous, or trees that lose their leaves in the winter. Deciduous trees allow up to 80% of the sunlight through in winter when their leaves have fallen off, thus letting the warm rays of the sun through to warm your home in the winter. To point out the obvious, people who have solar panels to create energy do not want shade trees blocking the energy-producing sun.
Various studies have focused on tree and shrub impacts on wind speed and its resulting heat loss in the winter. They conclude that, in a well insulated home, up to half of the heat loss is the result of heat exchange with outside air and that high wind speed directly increased the heat loss. Again, the results of the studies vary, but they all conclude that well placed conifers (evergreen) trees and shrubs on the north side of the building serve as a wind break and buffer the impacts of the strong prevailing winds during the cold winter months.
Trees planted along the city’s thoroughfares help reduce the impacts of the urban heat bank, thus reducing the overall outside temperature, including making for cooler nights. Think about all the asphalt streets, sidewalks, and brick buildings baking in the hot sun all day long. Even though the temperature may cool at night, the heat remains in stone and doesn’t allow the temperature to cool down. That is why the meteorologists will show the temperatures remaining warm throughout the night in the urban areas, while the suburbs cool down for comfortable sleeping. My wife and I have seen this effect ourselves right here in Medford. We try to walk many nights rather than watch television. We have a regular route and on hot nights the heat can be stifling as we walk down through Medford Square. We then head up to the backside of the Lawrence Estates along the edge of the Middlesex Fells woods where there is a thick tree canopy and limited sidewalks. There, the temperature is noticeably cooler by a good 5 to 10 degrees from what we experienced in the Square.
Fortunately, the City of Medford has an aggressive shade tree planting program that helps the quality of life in our community. According to Medford’s tree warden, Aggie Tuden, the City planted 118 new trees last year. Equally as impressive is that the city planted 16 different species and a total of 27 different varieties. It is part of a strategic plan to plant the “right tree in the right spot.” As a side note, the diversity in the plantings is not only aesthetically pleasing but also protects the city from a widespread tree blight or insect infestation that could wipe out entire species of trees, like the Asian Longhorned Beetle.
Beyond the energy savings and comfort benefits that trees and shrubs bring, there are other advantages for homeowners. Tree and shrubs act as a very effective noise barrier. According to EPA, a well placed row of trees and shrubs can reduce noise levels by up to 5 decibels and the wider or thicker the plantings the greater the noise reduction. We live fairly close to Route 93 and I have noticed that the noise from the highway in my backyard is substantially lower when the trees are leafed out in the spring and summer compared to the leafless trees of winter. Trees and shrubs also help reduce storm water runoff by intercepting over 35% of rainfall, according to a study in Sacramento, California. So, trees planted in Medford will help reduce dirty street run off which is a major source of pollution for the Mystic River.
Finally, a survey of studies by EPA, found “general’ increases in residential property values ranging from 3% to 10% associated with the presence of trees and vegetation on the property.
While I have focused on the benefits to the individual homeowners, there is a greater good that can be achieved. It has been estimated that 40% of the energy used in the United States is consumed in the operation of buildings and just under half of that energy is for heating, cooling and ventilation. Even, for the sake of arguments, if the studies are overly optimistic on projections the potential reductions in energy consumption are very substantial and that is all good. It reduces our carbon footprint, reduces green house gases, reduces our dependency on foreign energy, and yes, saves us all some money.
As the blistering hot days of summer fade behind us, fall is a good time to plant. There is a wealth of information on the Internet on how, where, and what kind of trees and shrubs work best for your yard. It’s well worth a look.
–Fred Laskey