Common Questions and Answers

LiveRoof® Common Questions

What’s so special about the LiveRoof® system?
With its unique patent pending Soil Elevators™ and Moisture Portals™, the LiveRoof® system gives you the look and function of a conventional green roof “membrane” system, with the turn-key benefits of a modular system. LiveRoof® represents the best aspects of modular and conventional green roofs combined in one simple, attractive effective system. LiveRoof® is an integrated system designed by growers in conjunction with experts in the fields of architecture, roofing, logistics, and ergonomics. It is designed to grow plants! Composed of recycled plastic materials, LiveRoof® is based upon sound horticultural principles. It is earth-friendly, as well as rooftop functional and aesthetically pleasing. LiveRoof® systems, because they are pre-vegetated at the nursery, require minimal maintenance. Compared to site-built green roofs, which are time-consuming and costly to install and maintain, LiveRoof® offers a turn-key alternative that doesn’t require you to be a horticulturist. LiveRoof® modules can be vegetated with various plant assortments to address your particular design needs and climate. And if there is ever any need to make changes to the roof, LiveRoof® modules are easily moved aside and replaced after the work is done.

What is the biggest financial advantage of LiveRoof®?
LiveRoof extends the lifetime of the roof; typical estimates are that a green roof extends the lifetime of a roof between 100 and 200 percent, by protecting the rooftop from ultraviolet radiation, large temperature fluctuations, drying winds, and punctures. Not only does the roof last longer, but there is reduced membrane maintenance. All this brings about significant cost savings over time.

Energy savings - What Can I Expect?
Green roofs have been proven to bring about significant energy savings, particularly during the summer cooling season in which single story buildings can experience a reduction of greater than 25% energy use. Plants transform heat and soil moisture into humidity, to create natural evaporative cooling. Each gallon of water that is transpired by the plants or evaporated from the roof surface liberates 8000 BTU of thermal energy.

Why doesn’t the LiveRoof® system use filter cloth? And, won’t the soil run out the drain slots?
Filter cloth, like any filter, is designed to filter. Filters in time can plug up (think of your car’s air and oil filters, your furnace filter, coffee filter, etc.). When a green roof filter plugs up, then what? Hint... bathtub (ok for water lilies, but not ok for green roof plants).

Because of the aggregate nature of LiveRoof® soil, the soil stays in the LiveRoof® module as it would if you poured it into a funnel. It’s like the square peg in a round hole scenario. In addition to this simple act of physics, the roots of your LiveRoof® plants bind the soil together and hold it in place.

Why doesn’t the LiveRoof® container have moisture reservoirs? 
Because it was designed by horticulturists. Horticulturists know that moisture reservoirs store water. Stored water is oxygen deprived, and roots sitting in oxygen deprived water become diseased with fungal and bacterial rot. This weakens the plant, may spread to the crown of the plant, and may perpetually handicap the plant and predispose it to secondary disease and insect infestation.

What is so special about LiveRoof soil?
Unlike cheap soils that are marketed as light weight, and packed with peat moss and perlite, LiveRoof® soil is predominately composed of high quality inorganic aggregates, contains a special clay particle to bind nutrients, contains an acid rain buffering component, and is formulated with disease suppressive organic material at a level that is consistent with ecologically sustainable soil/plant communities. LiveRoof® soil is designed to last indefinitely and to not substantially shrink over time. Cheap mixes with high levels of peat and compost will decompose and wash away as humic acid. Perlite after several freeze thaw cycles may shatter repeatedly and turn to dust. It may also float to the soil surface after heavy rains, then blow away when conditions are dry and windy. Note: regional adapatations of LiveRoof engineered soil will vary somewhat in composition. Each is specifically developed based upon climate, water quality, and regionally availabe components.

How much does the LiveRoof® system weigh?
The LiveRoof® system weighs approximately 23-29lbs./sq. ft. (with a media depth of 4”) when fully vegetated and saturated. The LiveRoof® soil follows FLL standards, enhanced to reflect current research regarding sustainable organic content. We have intentionally avoided excessive organic content, which will shrink excessively over time due to decomposition. Likewise, we have avoided perlite which may break down during the freeze thaw cycle.

Can I retrofit my existing building?
It depends on the load capacity of the existing building. Also, some older buildings can be redesigned for the additional weight of the LiveRoof® modules. A qualified engineer must always conduct a thorough analysis.

Does LiveRoof® need irrigation?
The need for irrigation (beyond normal rainfall) will depend upon the plants selected, the local climate, and specific weather patterns. Under normal circumstances, supplemental irrigation is seldom if ever required. Even so, we suggest a backup irrigation system in the event of prolonged hot, dry, windy, sunny weather. During very long bouts of dry weather, plants can go dormant, shrink up, and expose soil. This can increase maintenance requirements as weeds can become established in bare soil. Excessively dry soil also causes the evapotranspirative cooling effect of the green roof to be reduced. 

Irrigating, even once per month during protracted dry weather, can keep your green roof looking its best and pay dividends through maintenance reductions and evaporative cooling. Irrigating during protracted hot dry weather is a personal choice, the cost is minimal and one has the piece of mind that if ever needed, the water will be there. Backup irrigation systems can range from spigot and hose to overhead irrigation (similar to what one might have in one’s yard.)

What are the best plants to use with the LiveRoof® System?
Those that have extreme drought resistance through some means other than the root system. This means succulent, water-holding plants like Sedums, Alliums, Sempervivums, Delospermas and a few others. The best LiveRoof® plants will both store water and have a special type of metabolism called ‘Crassulacean Acid Metabolism’, CAM for short. CAM plants are unique in that under drought conditions their stomates (leaf pores) are open at night rather then during the day, as is the case with most plants. CAM plants exchange gasses (oxygen and carbon dioxide) in the dark when it is cooler and less windy. CAM plants are up to ten times more efficient with water conservation than non-CAM plants. (Continued on next page)

LiveRoof® plants have been selected for extreme drought tolerance, disease and insect resistance, long life, low maintenance, and beauty. LiveRoof® plants are planted in the LiveRoof® modules at Hortech and other nurseries and cared for until shipped to the job site. Plants are selected by local horticulturists in order to meet the above objectives as well as the local climate and customer preferences.

What is the urban heat island effect?
Simply put, it is the temperature difference that exists between urban areas and their surroundings. Urban areas tend to be from 7 to 10 degrees hotter due to the concentration of heat-absorbing buildings, pavement, and hot air from cooling systems. The bubble of hot air that encloses cities is in large part due to lack of vegetation and is a great contributor to smog, ozone and dust (from artificially created air currents from the rising hot air). The urban heat island effect has also been shown to create unique weather patterns within the city, with drought, high winds and electrical storms being more common than surrounding rural areas.

How does the LiveRoof® system help mitigate the urban heat island effect?
Traditional rooftops are usually covered with tar, shingles or stone. As a result, they absorb sunlight. On sunny days with an air temperature of 95°F, city roofs can easily reach temperatures of 175°F or more. The LiveRoof® system acts like a protective umbrella above the roof to shade and insulate buildings, avoiding the heat island effect associated with traditional rooftops.

Plants, of course, release oxygen and evaporate water, a process known as evapotranspiration, and act like evaporative cooling systems to make the air surrounding them considerably cooler. By implementing a LiveRoof® system, the combined benefit of eliminating the heat generated by a non-vegetated rooftop, along with the evaporative cooling effect, is significant.

How does the LiveRoof® system reduce storm water runoff?
In urban areas, impermeable surfaces (streets, sidewalks, rooftops etc.) dominate the landscape, preventing rainwater from following a natural cycle of absorption. Instead, as much as 75% of the rainwater runs into sewer systems. Carrying contaminates from the air and roadways (salt, oil, mercury, etc.), this water flows untreated into lakes and streams. In some cases, it may cause overflows of sanitary sewer systems, causing the dumping of untreated sewage. In contrast, LiveRoof® green roof surfaces can absorb up to 99% of a 1” rainfall, reduce runoff, lessen the risk of sewer overflows and flooding, and to some degree filter the water as it percolates through the LiveRoof® soil. Even when a rainfall is such that it can not all be absorbed by your LiveRoof®, the excess rain that runs through the media is filtered and delayed until after peak flows, which allows additional time for sanitary sewer systems to handle uncontrolled runoff.

How does the LiveRoof® system reduce noise?
Plants, soil, and trapped air and moisture in the soil are great acoustic insulators. Studies have shown that green roofs can reduce indoor sound by as much as 40 decibels, a benefit not lost on those that work close to overhead highways and airports.

Where can the LiveRoof® system be used?
LiveRoof® works well on low-sloped (non-pitched) roofs, on industrial, commercial, institutional, governmental and residential buildings. LiveRoof® works on any building where the building is appropriately engineered and the owners are progressive-minded and value the any economic, environmental, and health benefits that come from vegetated roofs.

Can the LiveRoof® system be used in nonroof areas?
Certainly—median strips, patios, plazas, and malls are also great opportunities to use the LiveRoof® system.

Can I lift up a LiveRoof® module if I want to access my roof? 
Yes, it’s relatively easy. First, using a flat bladed shovel, probe the planting to locate the container edge. Then peel away some plant material. This is easy to do as the root systems of LiveRoof® plants is fibrous and easy to separate (not at all like sod). Using a sturdy pair of pliers, lift up and remove the exposed module. Any additional modules may be removed by trimming around them with the handle of a spoon and lifting them up. Once you are finished, replace the modules. Note: Never use sharp intruments around roof membranes.

What incentives are available for green roofs?
As energy demands rise and smog and other pollution impacts our cities, many cities and states are encouraging “green” building methods, including green roof systems. Cities also encourage green roofs to reduce storm water surges, to protect the ground water, lakes, and streams, and to conserve energy.

Of course, incentives vary from city to city and state to state, but it is not uncommon for owners of buildings with green roofs to be generously rewarded. The city of Portland, OR, provides financial, technical and educational incentives to participants through its green roof initiative. Washington, Illinois, New York, Montreal, California and Maryland have also implemented incentive structures. Cities all across North America are following suit, and grant money is often available for the energy conservation and air and water quality benefits that green roofs bring. Be sure to check with your state and local governments to see what is in place in your area. Don’t assume that nothing is available. States and municipalities benefit greatly from green roofs, and often provide tax credits, avoidance of fees assessed for impervious surfaces, grant funding, and/or favorable zoning to encourage their development.

Can LiveRoof® modules be cut to fit odd dimensions and angles?
Yes, LiveRoof® modules can be cut to size and shape, either while pre-vegetated or empty with the use of a radial arm saw (with masonry blade) or reciprocating saw. When custom cutting LiveRoof® modules, the cut side should abut the non-cut side of another module, in order to contain the soil and minimize the work of installation.

If the cut side ever abuts edging, it should not be edging that is located on the low, draining side of the roof. Always fit modules tightly against edging or parapet or surround with drainage fabric for added security.

Can I walk upon my LiveRoof plants?
Yes, you can do this a couple times a week without causing permanent harm. If you want to pamper your plantings and avoid foot prints, make yourself a small pair of “snowshoes” out of plywood. Make them about 8 x 14 inches and attach some elastic cord to strap them to your feet. This will spread out your weight and protect your plants. Note: Be careful walking in such “shoes”, it will be a bit awkward and you don’t want to fall off of the roof. Always follow OSHA guidelines: “tether” yourself when working near the roof edge.

How do I go about having a LiveRoof® system installed?
Call the LiveRoof grower, installer, or architect nearest to your city and state. See Jim Costello at Prides Corner Farms