Cooling with Green Roofs for Commercial Buildings Simplified

Posted August 2, 2011, 8:46am EDT

Source: Monster Commercial

Making Green Roofs Simple; Green roofing systems (GRS’s) describes roofs that are substantially covered by vegetation which helps to combat the urban “heat island” effect and detain stormwater.  

The shading and cooling value of the vegetative cover provided by GRS’s can reduce building energy consumption and protect the roof surface, thereby extending its useful life.

GRS’s are a sustainable building technology that can be universally employed to save energy and improve air quality. They moderate the warming effects that exist due to pavement, structures and surfaces that absorb heat during the day and release it at night.

In the past “built-in-place” GRS’s had limitations, such as the complicated engineering and logistics associated with their installation and generally they were quite heavy.

Many major cities in NA including Toronto have also recognized the benefits of green roofs and have created economic incentives to promote their continued use. Tokyo for instance mandates that new construction with a roof area greater than 10,000 square feet include cultivation on at least 20 percent of that area. The same is true for Chicago, Seattle and Portland.

Recent developments in “modular” GRS technology promise to address these limitations and reduce costs by simplifying while maintaining the environmental benefits. There are a growing number of GRS projects are utilizing innovative, modular green roof systems to meet sustainability objectives.

As a result many building owners have capitalized on the benefits and GRS’s have begun to enhance the urban landscape.

Building owners in Europe understand why GRS’s are smart business. In Germany, for example, 7 percent of all newly constructed flat roofs are green. As a result, Germany now has 140,000,000 square feet of GRS’s with warranties up to 30 years, testifying to their durability.

Many major cities in NA including Toronto have also recognized the benefits of green roofs and have created economic incentives to promote their continued use. Tokyo for instance, mandates that new construction with a roof area greater than 10,000 square feet include cultivation on at least 20 percent of that area. The same is true for Chicago, Seattle and Portland.

Benefits of Greening Your Roof

GRS’s contribute to a building’s energy efficiency by shading the roof, and by providing evaporative cooling via transpiration. The combined effect substantially reduces summertime roof temperatures and lowers energy demands in areas directly below a green roof.

(A study conducted by NRC found that a 4-inch soil depth green roof reduced average daily energy demand for space conditioning by 75 percent. The effect was most noticeable during the summer months.)

The lower roof surface temperatures translate into lower surrounding area temperatures, reduced energy demand, and extended roof life.

They are also highly effective at managing stormwater discharge from a roof, thereby protecting sensitive watersheds and potentially reducing costs of drainage basins and other stormwater management structures.

GRS’s can reduce the levels of indoor sound by as much as 40 decibels, making for a healthier work or living environment. Green roofs are able to reduce the noise entering a building due to the insulating buffer provided by the plants and the soil media.

Another noteworthy benefit of GRS’s is improved air quality. Smog forming chemicals such as oxides of nitrogen and sulfur, as well as carbon dioxide are taken up directly by plants, lowering their concentrations in the air.

Conventional GRS’s

Most conventional GRS’s utilized a series of components that must be installed in layers on a roof surface and drawbacks include complicated installation logistics, excess weight, and lengthy installation schedules.

The number and types of materials that must be mobilized to the roof complicate the installation of built-in-place systems.

The layers of components used in a built-in-place GRS’s tend to be heavy and retrofitting an existing roof may not be feasible if the structural capacity of the roof is not adequate.

Repair and maintenance of the underlying roof can be cumbersome and costly since peeling back or replacing large sections of green roofing may be required.

Modular Green Roof Solutions

As a result, modular green roof technologies are rapidly gaining popularity. Modular systems retain all the benefits while addressing the limitations of a built-in-place system.

The benefits are simplicity and flexibility. Pre-planted modules are commercially available in various sizes that are easily installed in a wide array of configurations. Plants are established and mature in the module prior to placement on the roof.

The installation of the modular green roof can be completed in a matter of days or weeks and modules can be installed at any time during the year.

Using modular technology also eliminates difficulties associated with accessing a green roof’s waterproofing deck. If the deck needs to be maintained or repaired, only the modules immediately above the affected area need to be moved.

As communities push for increased energy efficiency, cleaner air and water, and more sustainable building technologies, building owners stand to make a dramatic contribution to the success of these initiatives.

In urban areas and areas of concentrated development, even small improvements in energy efficiency or decreases in air and water pollution, widely applied, can have an immediate and significant impact on quality of life in the built environment.

GRS’s offer a range of benefits that make good business sense and credits and rebates offered by some cities utilities provide even more incentive by reducing capital costs.

Research suggests that green roofs may be one of the fastest and most cost effective means of improving environmental quality and contributing to a large-scale transformation in the urban environment.