By Todd Shepherd | Colorado Watchdog
DENVER — The Denver Housing Authority is installing dozens upon dozens of solar panels on the Quigg Newton subsidized housing project near I-70 and Pecos. But as the solar panels go up, trees are coming down to accommodate them — a move that could ultimately raise the energy needs of at least some of the housing units.
It’s a battle between new green technologies and the oldest of green technologies.
“For optimal solar power production, it was determined that between 100-120 trees may be trimmed or removed for the total DHA solar project, which includes 668 solar electric systems on 387 DHA resident buildings,” DHA Community Affairs Officer Stella Madrid wrote in an email. “As DHA continues to assess the need for trimming and removal of trees at each of the solar installation, we will utilize the ‘Right Tree, Right Place, Right Way’ approach to minimize the removal of trees and maximize the solar panels.”
But this 1997 scientific study from the Lawrence Berkley National Laboratory found that trees providing direct shade to a home can save 30 percent seasonally on energy costs related to heating and cooling. A more recent study, as pointed out by a commenter on this story, estimates the summertime energy savings at about 5 percent. Either way, it seems safe to conclude that removal of trees and tree limbs at the sites of the solar panel installations may actually increase overall energy consumption.
The DHA’s Madrid acknowledges the tree removal and trimming comes with an impact.
“While there may be some impact to some units,” she wrote, “there are instances where there is zero impact (building facing north). Other building impact mitigation includes: (a) the units have insulated thermal-pane windows to reduce seasonal thermal transfer; (b) building insulation upgrade from R-19 to R-49; (c) Resident responsibility and resident education is ongoing to realize efficiency in heating and cooling. This includes promoting window shading to minimize or realize solar gain from direct sun light.”
One of the reasons deciduous trees are so efficient at providing year-round energy savings is because the shade in the summer obviously reduces the overall heat on the building, thereby reducing air conditioning needs. But as the seasons change and the leaves fall off, more sunlight is then allowed to filter in and warm the building during the colder fall and winter months.
There isn’t much middle ground between the choice of a shade tree that comes into contact with a solar installation. DHA notes that even a small amount of shade can greatly reduce the efficiency of a solar panel, and not just because the amount of available sunlight is reduced. Shade trees can cause parts of a solar panel to over-exert — a phenomenon called “hot spot damage” — which can then cause the panels to overheat or even burn out.
The Colorado Watchdog investigation began when residents said trees were being marked for removal. When asked if the markings indeed meant the trees would be removed, the agency gave an Orwellian response: Yes. And no. And maybe. “The designated markings indicate assessment for three action options,” Madrid wrote.”(1) tree trimming needed only; (2) no action needed; or (3) removal necessary to optimize solar panels.”
Not surprisingly, this isn’t the first time a tree-vs.-solar contest has emerged. As this Washington Post story details, the removal of shade trees to accommodate solar installations caused significant controversy in Takoma Park, Md., including disputes about city fines for tree removal. The Post called it a battle between “sun worshipers and tree huggers.”
DHA told Colorado Watchdog that the agency will plant “solar-friendly” trees this fall.
Hannah Glennon contributed to this report.