FREQUENTLY ASKED QUESTIONS
What is a green roof or an edible wall? As green roofs and living/edible walls receive more media attention and cities, healthcare providers, businesses, and homeowners begin to realize the environmental and social benefits we have received lots of calls and questions. To help answer them we have compiled a list of frequently asked questions to get you started. But don't worry, if you still have questions let us know and we'll try to help.
Green Roofs - Living Walls - Rainwater Harvesting
What are green roofs?
Green roofs, also called “vegetated roof covers,” “living roofs,” and “eco-roofs” are thin layers of living plants that are installed on top of conventional roofs. Properly designed, they are stable, living ecosystems that replicate many of the processes found in nature.
What are the major benefits and advantages of green roofs?
The green roof is the one building element that improves with age! Other benefits include:
• Controlling storm water runoff, erosion and pollution
• Improving water quality
• Mitigating urban heat-island effects, cooling and cleaning the air
• More than doubling the service life of the roof
• Conserving energy
• Reducing sound reflection and transmission
• Creating wildlife habitats
• Density bonuses
• Higher rental rates
• Marketing and PR value
• Increased property and building values
• Improving the aesthetic environment in both work and home settings
Can you earn LEED credits for building a green roof?
Yes! Green roofs can earn LEED credits in the following categories of the USGBC's green building rating system:
PART 1: SUSTAINABLE SITES
• Reduced Site Disturbance, Protect or Restore Open Space
• Reduced Site Distrubance, Development Footprint Credit
• Landscape Design That Reduces Urban Heat Islands
PART 2: WATER EFFICIENCY
• Storm Water Management
• Water Efficient Landscaping
• Water Use Reduction
• Innovative Wastewater Technologies
PART 3: ENERGY & ATMOSPHERE
• Optimize Energy Performance
• Renewable Energy
• CFC and Ozone Depleting Substance Reduction
PART 4: MATERIALS & RESOURCES
• Storage and Collection of Recyclables
• Recycled Content Materials
PART 5: INDOOR ENVIRONMENTAL QUALITY
PART 6: INNOVATION IN DESIGN
Are there proven, scientific standards for green roof design?
Presently, the only widely-accepted, established standards for green roof construction are those developed in Germany by the Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau. e.V. (FLL). These standards and guidelines are comprehensive, and include industry standard tests for the weight, moisture, nutrient content, and grain-size distribution of growing media. FLL also certifies laboratories to conduct critical tests, such as the root penetration resistance of waterproofing membranes.
Within the past few years, the American Standard Testing Methods (ASTM) convened a Green Roof Task Force to create green roof standards. Charlie Miller, P.E., President and founder of Roofscapes, Inc., (for whom we are licensed installers) has been a very active member of this Task Force from the beginning and has been instrumental in drafting these standards.
The methods described in the new ASTM standards establish a common basis for comparing fundamental green roof properties, such as maximum weight and moisture retention potential. These methods are designed to measure critical material properties for green roof materials under conditions similar to those encountered in the field.
How much does a green roof weigh?
Green roofs vary greatly in weight, depending on the product you choose, their depth and the material components. The important measurement is 'wet' weight -- fully-saturated fabrics and plants. For example, saturated weight of a 2-inch deep system is about 13 pounds per square foot, including a mature plant cover. Mid-range, 5-inch systems weigh approximately 34 pounds per square foot and are compatible with wood or steel decks.
How does a green roof affect the conventional roof below it?
Based on German experience, a green roof can be expected to double or triple the life of the underlying conventional roof by protecting from human activity and wind-blown debris; shielding from UV radiation; and buffering temperature extremes, thereby minimizing damage from daily expansion and contraction.
What kind of waterproofing do I need?
Many types of waterproofing are compatible with green roofs. World-wide, polyvinyl chloride (PVC) and polymer modified bituminous membranes are the most common. Many of these installations have now been in place for over 30 years and continue to perform as designed. PVC, EPDM and thermal polyolefin (TPO) are, in most cases, inherently root-resistant; other common waterproofing materials require a root barrier between the waterproofing materials and the vegetated cover.
Are leaks under a conventional green roof a problem?
Surprisingly, leaks in the waterproofing layer are less likely when it is protected from the elements by a green roof. If a leak does occur, it can readily be located through new electronic technology, such as electric field vector mapping (EFVM), which can rapidly and accurately pinpoint even minute holes. While GreenScaped Buildings implements flood testing prior to the installation of plants and growing media, the addition of an EFVM system is convenient, need not be installed in advance, and can even be used on steeply-sloped surfaces. Repairs to the waterproofing are quick, and disturbance of the green roof is minimal.
Why is drainage important?
Proper drainage ensures that the growing medium will be maintained in an aerated condition suited to healthy plant growth. Basal drainage must also be designed with large rainfall events in mind. The goal is for all rainfall to percolate to the base of the system. The portion that is not absorbed should move 'underground' toward roof drains or scuppers, and then into your rainwater harvesting system (if installed).
Is there a danger of dry plants catching and spreading fire?
Not if the green roof is designed correctly. In Germany, green roofs actually have a better fire rating than conventional roofs because the mineral media layers cannot burn. The extensive use of Sedums (a type of succulent) and gravel borders and breaks also protect against fire. In our arid, fire-prone region, we engineer the system with fire-retardant features, paying special attention to mineral content, gravel layers, and plant selection.
What kind of maintenance is required?
After the general two years it takes for plants to become established, most extensive green roofs only need weeding and occasional infill transplanting twice a year. GreenScaped Buildings can take care of these needs through our maintenance program. We also check the irrigation system and drains. Maintenance visits should be timed to intercept any weeds before they go to seed. This level of maintenance is sufficient to maintain the health of the plants and protect the underlying roofing materials. Some owners enjoy greater involvement and choose to 'garden' in their green roof more frequently. Intensive green roofs will require the same care and maintenance as a similar garden situated on the ground.
How much does a green roof cost?
Cost per square foot depends on many factors: the size and slope of the roof, depth and complexity of the system, height and accessibility from the ground, cost of labor, and need for specialized elements, such as drains, railings, pavers, slope stabilization measures, etc. Prices range from $10/square foot to $25/square foot.
LIVING AND EDIBLE WALLS
What are the benefits of living walls?
There are so many benefits associated with living walls. Among many of them, are that living walls conserve energy by insulating the building envelope, reducing the need for heating in the winter and cooling in the summer. They create biodiversity conservation opportunities, and absorb and filter storm water, which reduces local water body pollution and helps prevent the overwhelming of municipal storm water infrastructure. Living walls also filter air particulates, improving air quality and help to reduce the urban heat island effect (UHI).
What is the weight of a living wall panel?
GreenScaped Buildings uses two different living wall products to match your needs. Our shallow profile panels weigh approximately 5 pounds when empty, and the planted panels range from 35-45 pounds (13 to 16lbs per sq ft) depending on the type of growth medium used. Deep profile panels can weigh up to 60 pounds fully saturated.
Can the living wall kits be painted of stained?
Our shallow profile panels can also be ordered with several different frames which can be painted or stained to suit your décor. We suggest talking to you local paint dealer to help choose a product that will work best for you.
What plants do people plant in them?
Plant choice is always location and climate dependant so we look at each project individually. We generally use sedums and other rock garden perennials which have shallow root base for our shallow profile panels outdoors. Extended panels can be planted with a larger variety of perennials or annuals and also some of the shallow root grasses. We try in all cases to choose plants that are more drought tolerant as we are always encouraging water conservation. Native plants are also very helpful to habitat restoration efforts, as most native plants provide food for our local birds and butterflies. The factors that will affect your choices are your climate zone, irrigation supply, budget, and exposure. Our talented designers can help you choose the plants that are right for you. For indoor installations we use hardy tropical plants with shallow roots.
Can I grow vegetables in my living wall?
We have quite a few customers that are successfully growing lettuce, herbs, beets, radishes and carrots in their walls. Some are using extensions for the plants with deeper root base.
At our on-site Living Laboratory, our 8 -panel herb wall has been doing extremely well. We regularly harvest different types of mints, sage, salad greens, and several other types of herbs.
How are the walls watered?
The panels are designed to allow water flow from cell to cell within each panel and then from panel to panel in a complete wall. For direct mount wall installations we suggest the installation of drip irrigation lines between every row or every second row of panels depending on the micro climate of the installation.
How much water do the walls need?
The amount of water required is plant and climate dependent with an average of approximately 2 liters per panel per watering. Each cell has a water retention area so that it holds water when it flows through the panels. Keep an eye on your plants! If they look sad, they probably need water.
What are the maintenance requirements?
With carefully selected plants and proper irrigation, living walls can be virtually self-sustaining. The only thing that may need to be done is the odd trimming of dead leaves or fertilizing, or adding plants as necessary if replacements are needed. It is very similar to house or garden plants in that way.
What kind of light do I need for my living wall?
It is best to locate your wall where it will receive some natural light. Otherwise you can augment with artificial if necessary. The most important thing is to specify plants that will survive where you are planting them. There are some species that survive very well for instance in low light. Others require more light. When in doubt – call us!
What is rainwater harvesting?
'Rainwater Harvesting' refers to the collection and storage of rain. Collection is usually from rooftops, and storage in catchment tanks. Stored water can be used for non-potable purposes such as irrigating lawns, washing cars, or flushing toilets. Rainwater harvesting systems can range from a simple barrel at the bottom of a downspout to multiple tanks with pumps and controls. Before the creation of public water utilities, rainwater harvesting provided water for many American homes. It is still popular in places with limited water resources such as island communities like Hawaii. In our arid climate, recent drought conditions remind us how quickly we can run short of water.
Using purified potable water for purposes like flushing toilets or irrigating landscape is a waste of a valuable resource, and San Diego residents are asking more questions about the role of rainwater harvesting in their daily water needs. Rainwater harvesting is also effective in reducing storm water runoff pollution. When rain falls, it is clean, but it immediately picks up pollutants from rooftops and pavement. This pollution is carried into storm drains and then into streams. Collecting storm water from rooftops and directing it to storage tanks so it can later be used for irrigation or flushing decreases the volume and rate of runoff.
How much water can I save?
The City of Portland, Oregon has numerous incentives in place for rainwater harvesting systems. Use their following formula to estimate your annual water supply:
Collection Area (sq. ft) x Rainfall (in/yr.) / 12 (in/ft) = Cubic Feet of Water/Year
Cubic Feet/Year x 7.43 (Gallons/Cubic Foot) = Gallons/Year
For example, a 500 sq. ft roof that gets 36 in/yr. will produce 1,500 Cubic Feet or 11,145 Gallons of water per year.
PLEASE NOTE: This calculation is for horizontal areas and does not take into consideration system losses such as evaporation or leakage.