Monday, December 9, 2013

Green Roofs

A green roof is an addition of a new or existing roof that involves high-quality water proofing, a root repellent system, a drainage system, filter cloth, a lightweight growing medium and plants. Green roof systems may be modular with drainage layers, filter cloth, growing media and plants already prepared in movable, interlocking grids, or each component may be installed separately. Green roof development involves the creation of contained green space on top of a human-made structure. This green space could be below, at or above grade, but in all cases the plants are not planted in the ground.

There is no single type of green roof that works for all buildings, climates and client needs. Green roofs can be categorized as intensive or extensive, depending on the depth of growing medium. Six inches or less growing medium depth is an extensive roof, also characterized by its lower weight, lower plant diversity, cost and maintenance. Intensive green roofs have more than 12 inches of growing media and tend to have higher plant diversity, higher weight, cost and maintenance.

One benefit green roofs provide is increased savings on heating and cooling energy costs. Results vary according to size of the building, climate and type of green roof, but a Michigan State University study finds  that a typical one-story building with a grass roof and four inches of growing medium would result in a 25% reduction in summer cooling needs. Field experiments found that a 6-inch extensive green roof reduced heat gains by 95% and heat losses by 26% compared to a conventional reference roof.

Green roofs decrease the cost of meeting greenhouse gas reductions and adapting to climate change by reducing the urban heat island effect -- the phenomenon of metropolitan areas being significantly warmer than surrounding rural areas, due to the heat-reflecting nature of concrete and other man-made materials and the release of heat from AC systems. The reintroduction of vegetation into cities promotes natural cooling by absorbing, instead of reflecting, the sun's rays, and through evapotranspiration. Traditional black roofs can reach temperatures of 158°F. One study concluded that 25% green roof coverage can reduce the urban heat island effect by up to 3 degrees F. Green roofs can also mitigate air pollution levels by trapping particulates and capturing harmful gases.

Milwaukee is a city that has a combined sewer system (the deep tunnel), whose treatment capacity can be overwhelmed by heavy precipitation, resulting in overflows into Lake Michigan with untreated waste water. By capturing and temporarily storing storm water, green roofs can reduce run-off volumes, thereby reducing the occurrence of combined sewer overflow events. By reducing peak flows, green roofs can also reduce the incidence of flooding and damage by erosion.

Green roofs filter storm water, improving the quality of the run-off. Studies have shown that a conventional roof's run-off contains high concentrations of pollutants from rainwater, roofing materials and atmospheric deposition. The plants and growing media used in green roofs help decontaminate run-off, loading fewer pollutants into the municipal storm water system.

Another cool application is rooftop agriculture, which can help mitigate the negative impacts of urban sprawl, ensure heightened food security and engage communities in the food production process. Given that at-grade land in urban centers is at a premium for development, roofs are a logical location for urban agriculture. Urban food production reduces the uncertainty associated with long-distance food supply, including supply interruptions. Rooftop community gardens can help meet nutritional requirements and reduce household expenditures on food, while creating accessible meeting places and activity areas that can increase social interaction and community cohesion.

Jeff Miller

Monday, April 8, 2013

First the Cold, Now the Mold!

As winter (finally!) comes to an end, many homeowners are dealing with another kind of “white stuff” on their lawn:  mold.  There are two types of snow mold:  Grey Snow Mold (Typhula blight) and Pink Snow Mold (Fusarium patch), both of which are fungal diseases that are common in spring lawns.

Snow mold develops when there is an extended period of snow cover on ground that is not completely frozen. It can also be brought on if a lawn is not properly prepared for winter.  For example, a badly timed fertilizer application can cause a flush of growth too late in the fall.  Snow mold can also thrive under leaves that have not been cleaned up or in long grass that should have been mowed one last time before winter set in.
Seeing Spots?
Snow mold damage looks like circular patches of dead, matted grass. It is not unusual to find both gray and pink snow mold together.  While both are more or less white, grey-hued snow mold only infects the leafs of grass while pink snow mold does more damage because it attacks the entire crown of the plant.
Pink snow mold is distinguished by the pink color of the web-like mycelium growing on the grass surface. When the grass is wet, the moldy growth looks like white cobwebs, but it turns pink as it matures then disappears when the grass dries.  Gray snow mold is similar, except its mycelium stays whitish-gray and it produces tiny black mycelial masses (sclerotia) on the grass blades.
Spring Cleaning!
Fungicides are available to both prevent and treat snow mold, but because the damage is largely superficial and temporary, you’re probably better off handling it with a little spring cleaning in your yard.  Simply raking the infected area will remove thatch and debris and speed up the drying process – once the grass is dry, the mold will dry up too and your lawn will then grow out and renew itself.  Some overseeding may be necessary or, if there is a great deal of damage, topdressing can be applied and areas can be repaired like a bare patch.
Although it can look really nasty, most snow mold damage will recover with little or no work on your part.  If that’s not enough of a silver lining, just remember that it’s also a sure sign of spring and warmer days are certainly on the way!