Green roof inspiration for homes, sheds and arbors

In Germany, it is estimated 12% of all flat-roofed buildings are living roofs, a number that is rapidly increasing as the German green roof industry continues to grow 10 to 15% per year.

There are two main types of green roofs.

Intensive (labor-intensive) – Found on flat roofs and require about 4-24 inches of planting medium that is able to grow conventional lawns, vegetable gardens, small shrubs and even small trees. Intensive rooftops require sophisticated structural support and possibly irrigation. Typically weigh 80-120 lbs. per square foot, fully saturated. Are often park-like gardens for public or private use.

Extensive (sedum or grass) – Designed to be virtually self-sustaining and require low to no-maintenance. Needs a planting medium of 1-4 inches on a flat or gently sloping roof. Best with native vegetation or drought-resistant, cold-resistent, shallow-rooted plants, sedum, herbs, mosses or grass which generally grow no higher than several inches. They typically weigh 10-50 lbs. per square foot, fully saturated, depending on what type of growing medium is used.

Benefits:

Green roofs are excellent insulators. Studies have shown that a green roof can reduce your cooling costs by 50% and more during the summer months and in the winter your home will retain 15-30% more heat than if you had a conventional roof. On a sunny, 80-degree-F day, a black roof can reach 180 degrees F; a white roof 120 degrees; and a plant-covered roof 85 degrees. Save money and use fewer energy resources.

Cost. There are many modular green roof kits available that might bring the costs down. Extensive green roof: $8 to $20 per square foot. Intensive green roof: $15 to $50 per square foot. A 2006 study by the University of Michigan comparing costs of conventional and green roofs showed that, on average, installing a green roof costs about $22.00/sq. ft. versus $16.00/sq. ft. for a conventional roof. In its life, however, it was estimated the green roof would save over $200,000 (in 2006 energy prices) with two-thirds of that coming from reduced energy needs.

Reduced storm water runoff. When the water falls on a typical roof, it’s often funneled off into storm water drains, collecting pollution along the way and polluting our waterways or increasing the amount of sewage to be treated. Green roofs ‘harvest’ rain water and put it to beneficial use.

Increased longevity of roofing membranes. The plants and growing medium are absorbing the solar rays, protecting the roofing materials from UV breakdown.The green roof also shields the membrane from extreme temperature variations, another cause of hastened degradation. According to Penn State research, a green roof will lengthen roof life by two to three times.*
Sound proofing. An extensive green roof can reduce sound from outside by 40 decibels, while an intensive roof can reduce sound by 46-50 decibels (Peck et al. 1999).

Aesthetic appeal. Nature relaxes, promoting psychological well-being.

Carbon is sequestered.  Through the process of photosynthesis, carbon dioxide is removed from the atmosphere and stored as carbon in biomass.

Urban Heat Island Effect – if an urban area has numerous green roofs, heat island effect is lowered.

Habitat. When planted with native vegetation – a green roof becomes a habitat for indigenous species and migrating butterflies, birds and bees.

Resources:

Green Roofs for Healthy Cities greenroofs.org
GreenRoofs.com greenroofs.com

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