Investigating the Dangers of Green Roofs and Walls (Groof)
Should you know us through our Blog by now - we like to show we that we prefer to do the heavy lifting for our clients. We recently summarized some articles about the cons, downsides, dangers, and failures of both green roofs and green walls in the last decade, so our readers can get a head start. Below, you’ll find the article in reference along with our favourite excerpts from those articles. Please go to the articles directly to read them in entirety.
RETHINKING GREEN ROOFS: 9 points to consider before greening your roof | Green Building Canada
“can reduce roof temperatures from summertime highs of 150 degrees to less than 80 degrees, can reduce energy demand by more than 50 per cent annually, can minimize impact on microclimate and natural surroundings and can increase oxygen through photosynthesis.”
“Can”? That little three-letter word as recruited above could also mean “might not,” probably won’t,” “wouldn’t in a million years,” and a host of other adverse implications.
“1. Green roofs cost a lot. Typically 15 to 25 dollars per square foot on top of one’s initial cost. This could tilt the scales of this shelter’s potential cost-effectiveness from positive to negative.
2. These roofs weigh a lot. Usually 40 to 80 pounds per square foot, some as much as 200 psf; and all supporting structure below down to the ground must be made larger. To indicate how deceptive some promotions of green roofs have been regarding this, consider the recently built green roof on the Chicago City Hall, an impressive project that received rave reviews in numerous architectural magazines. However, only one of these periodicals mentioned (in a short sentence sequestered deep in its text) that what made all this heavy construction possible was that the building was originally designed to support the construction of an added floor; and the weight of the green roof replaced what would have otherwise been the weight of the future floor without requiring any revisions in the structure below. Every article about this roof should have made this vital point clear. Or else—again—when someone who constructs this idea learns that it or some other ecologically promoted concept isn’t what they were led to believe, the tide of one’s opinion will likely turn from delight to dissent, and in the company of one’s colleagues they will colloquially cast a vote against rather than for the reality—often with a fervour that far outweighs any feeling they might have otherwise expressed; for in such scenarios, censure generally outpaces praise.
3. Topsoil can erode and subsoil can slip during heavy rains. Though LEED’s guidebook says, “All garden roofs decrease stormwater runoff volumes substantially,” this is false. Garden roofs may decrease stormwater runoff during short light rains; but during severe storms when the roof’s soil has become saturated, stormwater runoff will not be less than on standard roofs and this is when topsoils and subsoils will likely erode and slip.
4. After construction most green roofs need almost daily horticultural attention: mowing, weeding, erosion control, and precise watering (enough to encourage growing but not enough to initiate erosion and slippage).
5. Green roofs attract bugs, rodents, and other members of a thriving ecosystem, even on tall buildings.
6. Green roofs require access—not by a ladder over a gutter but by a railed central staircase. A good central entry is a stairwell that rises into a small greenhouse with a door from which you step onto the roof. Also, areas that can be occupied should be enclosed by chest-high parapets; and any walkways or terraces should be masonry and not wood, which requires waterproofing above, airspaces below, and toxic rot-proofing all around.
7. These roofs often require electric outlets, landscape lights, hose outlets, and related mechanical equipment.
8. The roof substrate can leak, and when it does it is difficult and expensive to repair.
9. A green roof can be a fire hazard. If the roof’s vegetation turns brown due to lack of water, a brush fire could start there and spread indoors or to other buildings.”
Also:
a) “Some green roofs have grasses and plants that require no watering,” (False: all plants, even cactus, require some watering, which means monitoring, which means access).
b) “All types of green roofs have longer lifetimes than conventional roofs,” (False: if they do last longer it is because they must be constantly maintained in ways that are not required with standard roofs).
c) “Green roofs provide lower maintenance than standard roofs.” Hah! See #4 above.
“If you want a green roof to increase a building’s insulating ability and decrease its water runoff, there are better and cheaper ways to do these things. Esteemed building scientist, Joseph Lstiburek, Ph.D. says:
Vegetative roofs? Grass and dirt are not energy efficient. Work with me here. Which saves more energy: two inches of dirt or two inches of insulation? Which saves more energy: grass or a white-coloured membrane? Which is more expensive and does not save energy: grass and dirt, or insulation and a white-coloured membrane? Which needs to be watered to keep the grass from dying and blowing away?”
To finish it off, we love this humorous, slightly less critical quote as well. Our next article on Groof.ca’s blog will focus on the upsides of green roofs/walls…
“On the other hand, if you love gardens and want to transform a barren tract wracked with violent temperature extremes into a meadowy landscape that blooms with wildflowers, bustles with butterflies and birds, is threaded with pleasant walks and patched with relaxing terraces, and offers fine views above the bugs and closer to the stars, then you deserve all the joys that gardens can give you, all the praise that periodicals may rain on you, and all the points that LEED may award you.”
2013 -
“A roof collapsed at a supermarket in Latvia’s capital, killing at least 48 people / cave-in of a 500 square-metre section of roof,"
potential causes. Among other issues, police are investigating whether poor supervision or the development of a roof garden may have played a role, BNS cited chief of State Police Ints Kuzis as saying.
Maxima Group, the biggest retailer in the Baltic states, runs 499 supermarkets in Lithuania, Latvia, Estonia, Bulgaria and Poland. It rents the premises from SIA Tinio and said building was taking place on the roof and in the underground parking area
Zolitūde shopping centre roof collapse - Wikipedia
According to Ivars Sergets, the owner of HND Grupa which was responsible for the construction of the building, the collapse may have been caused by overload, created by materials being loaded onto weaker points of the roof. He rejected the possibility that the disaster had been caused by the design of the garden, since the store had been operating for two winters and the stress created by the weight of snow had been up to twice as great as the stress caused by the garden at the time of the collapse. He pointed out that too many of the building materials were stored on the roof.[51] Later on, however, he admitted that trusses made of two pieces bolted together were used, while the original design called for a single truss. This was a result of issues with transporting longer trusses to the building site.[52]”
Green Roof Collapses in Illinois - The New York Times (nytimes.com)
Green roofs have become increasingly popular in the United States as a way to beautify and insulate buildings and reduce heat pollution in urban areas, but last week one drew attention for a far different reason: it collapsed.
A 700-by-50 foot section of a roof over a parking area buckled on Feb. 13 at a garden pond construction and supply company in St. Charles, Ill., west of Chicago. No one was injured in the collapse, which occurred on a Sunday afternoon when few people were working at the company, Aquascape.
Nearly a week later, investigators were still waiting to try to determine why the roof collapsed, said Ed Beaulieu, a company vice president. “We have to shore it up to make sure it’s safe” before the investigators can examine the steel structure, he said.
Mr. Beaulieu said the area had received a record snowfall and then, two weeks later, temperatures climbed above freezing. “The collapse happened right at the beginning of the thaw,” he said, leading to speculation that ice on the roof might have prevented meltwater from draining off. “But right now no one really knows.”
The building, which was constructed six years ago, has a 240,000-square-foot roof, roughly half of which was “green,” Mr. Beaulieu said. The collapsed area represented about one-quarter of that, he said.
Many green roofs are planted with water-retaining sedums or low grasses, but Aquaspace’s was planted with native Illinois tall grasses. “It was pretty unique,” he said. “In the summer there’d be birds, bees and butterflies up there. It looks like you’re in a meadow.”
Aquascape Inc.'s covered parking roof collapses - Garden Center (gardencentermag.com)
"Thank God it happened on a Sunday when we are closed," said Greg Wittstock, owner and CEO. "We are so thankful that no teammates or customers were here. Situations like this happen, it's how you respond that matters."
Aquascape Green Roof Failure (sustainableconstructionblog.com)
largest sloped green roof in North America collapsed.
snow had melted on the roof but could not drain because of ice blocking the drainage system.
Incidents such as the Aquascape green roof collapse should not discourage people from using sustainable products and technologies in new buildings but should emphasize the need for construction managers and contractors that are familiar with the new technology.
The green roof was planted with native Illinois prairie plants in six inches of soil, he says.
St. Charles firm sues for $13M after green roof collapse in 2011 (dailyherald.com)
Settlements reached in Aquascape roof collapse lawsuit – Shaw Local
Aquascape Sues Over Collapse of World's Largest Sloped Green Roof Near Chicago (inhabitat.com)
The companies involved in the lawsuit include Artisan Design Build LLC, Senekteks, Tricon Construction, Olsson Roofing, Tecza Environmental Group, Applied Ecological Services, Metallic Building Company, Area Erectors and Dewberry Architects, The Daily Herald reports. Let this be a lesson for companies throughout the United States that are rushing to add their own green roofs. Make sure your designer has good credentials!
Six subcontractors named in a $13 million lawsuit over a 2011 green roof collapse in St. Charles could be dismissed from litigation if a Kane County judge rules next month that they have reached good-faith settlements, according to court records.
The insurance carrier for Aquascape, a St. Charles-based water feature design firm, sued after part of the green roof covering a parking lot collapsed after a blizzard Feb. 12, 2011.
No one was hurt in the collapse at 901 Aqualand Way, which happened on a Sunday afternoon.
According to court records, six subcontractors -- Metallic Building Co., Tricon, Senektekts, Applied Ecological Services, Dewberry Architects and Olsson Roofing Co., were dismissed from the lawsuit last week, provided they can reach settlements and a judge finds the settlements were reached in good faith.
An exact number could be tallied Sept. 8, when Kane County Judge John Dalton holds a hearing.
"The case is still proceeding," said John Groark, attorney for Aquascape's insurance company. "The legal rulings have allowed subcontractors to pay a small part of the damages and get out of the case. The suit is still going against a couple of companies, Artisan being one of them."
The primary defendant in the case the Madison, Wisconsin-based, Artisan Design Build.
A message left with Artisan attorney Robert Martier was not immediately returned Wednesday. Area Erectors Inc. and Tecza Design Build also are still on the lawsuit.
After the collapse, Aquascape employees were moved to a temporary location while repairs were made.
Asked if a settlement could be reached with Artisan, Groark said: "It's always good if you can resolve a case. But both sides have to agree. Only time will tell."
The Sky is Falling: A Critique of Failed Sloped Extensive Green Roofs - Green Roof Technology
2011
One of the most infamous of these rooftop blunders was last winter in St. Charles, Illinois. The project was designed to be the largest sloped roof in the US and during a heavy snow storm the roof collapsed. Fortunately no one was hurt however the damage was devastating.
Why did the roof collapse? The problem lies in the drainage. Snow is frozen water and where you have more water accumulating on a roof you will also have greater amounts of snow accumulate. This insufficient or clogged drainage system and poor growing media is the most likely culprit in areas that held water or snow. All this added weight during an extreme winter put the roof way beyond its capacity.
Sadly, this situation and others like it could have been avoid simply by hiring a true expert and checking their performance history for similar projects.
Disadvantages of Green Roofs | Hunker
2021
But you don't just toss plants on the roof and let them grow. These roofs require drainage material and a waterproof membrane along with careful plant selection.
some disadvantages to installing green roofs that you should consider before you start planting.
Extensive green roofs often weigh less than standard gravel and tar roofs. Intensive green roofs, however, may require additional structural support.
Extensive green roofs often weigh less than standard gravel and tar roofs. Intensive green roofs, however, may require additional structural support.
You may save a little money on your heating and cooling bills, but you'll spend upfront to have the green roof installed. Installing a green roof can cost up to twice as much as installing a conventional roof. An extensive green roof generally costs between $10 to $24 per square foot. Intensive green roofs typically cost twice as much to install as extensive green roofs because of their thicker, more complex assembly.
Maintenance for intensive green roofs can be labor-intensive and expensive. Extensive roofs require less watering and fertilizing, but they require at least yearly inspections to remove unwanted self-seeding plants. Homeowners can reduce costs by weeding, fertilizing and watering plants themselves
Damage from Leaks
Although most green roofs include a root barrier layer, the roots of plants sometimes penetrate the waterproof membrane, causing roof leaks that could result in structural damage. A yearly inspection to remove problematic shrubs helps reduce the potential for developing leaks. A shallow growing medium usually prevents any plants from growing large enough to develop a strong, deep root system.
Because the green roof assembly is so complex, finding the source of a leak and repairing it can be a challenging process. Green roof installers can perform flood tests immediately after the installation or repair of a roof to check for leaks. Some companies offer leak detectors that use electronic charges to trace the path of a leak to its source.
Limited Choice of Plants
Another one of the disadvantages of green roofs is the available plant selection, especially if you choose an extensive system. The thick growing medium of intensive green roofs can support the growth of a wide range of plants, including shrubs and small trees. The thinner extensive green roofs, however, can typically only accommodate a small selection of drought-tolerant plants with shallow root systems.
Sedums, lichens, mosses and low-growing grasses are common choices for extensive roofs. They look less lush, leafy, and, to some, less attractive than the plants grown in deeper soil. Less robust plants may also have trouble surviving the strong winds common on high rooftops.
The investigation concluded that the collapse of the roof structure was caused by overloading, as a result of the following three factors: (i) The screeding of the roof structure was thicker than the original design; (ii) The laying of greenery cover on the roof; and (iii) Localised water ponding on the greenery cover.
The screeding, which was thicker than the original design, together with the laying of the greenery cover increased the loading imposed on the STS. As such, the gradient of the roof was reduced, which affected the rate and flow of water discharge, resulting in localised ponding on the greenery cover. Following the increase in the extent of water ponding on the greenery cover, the loading on the STS was further increased and finally exceeded the loading capacity of the STS, leading to the collapse incident.
The BD has issued a circular letter on "Roof Greening in Existing Buildings", reminding the building industry of the technical issues to be considered in designing and installing roof greening in existing buildings, such as structural issues, loading and drainage systems. To further enhance public awareness on greening in buildings, the BD has promulgated the "Introductory Guide on Greening in Buildings" on its website to provide an easy reference to the general public for safe provision of greening in buildings, and to remind the general public on the potential impact of greening on building safety, the areas of concern and the need to seek professional advice as necessary for ensuring building safety.
Such roofs are usually installed on top of other roofing materials and are available in various types. Some of the requirements for having green roofs include having very efficient drainage systems, waterproofing for the roof, a root repellent medium, and filter cloth. Without these, it will be impossible to experience green roofs benefits.
Despite their growing trend, some cities do not allow green roofs.
So, do green roofs really work? Yes. Research shows that they are more effective than other alternative strategies like planting trees on the streets. It is also a more viable option because it does not require roofing repair, and most important large pieces of land, which may not be easy to find in urban settings. However, you must consider the possible disadvantages of green roofing before installing one.
Do green roofs really work? Yes. Green roofs are better at maximizing the use of water, soil, and vegetation, making them better than traditional roofs. The two main factors that aid in this are heat storage and transfer in relation to soil properties.
Disadvantages of a Roof Garden (weekand.com)
The structure and weight of a roof garden can cause problems for the overall building. Soil and planting pots are both heavy -- whether you create a soil planting bed in your roof garden or use pots, you are significantly adding to the weight placed on the roof structure. Patio slabs and furniture further add to the weight on the roof. Most building roofs will require proper reinforcement before a roof garden can be grown safely. High roof gardens may have problems with high winds damaging plants and young seedlings.
A roof garden places a heavier strain on a building's water supply. If no water outlet is available on the roof, you will have to either install water in the roof garden or carry water from inside the building. A traditional land garden can drain freely, but a roof garden will require a special -- and expensive -- drainage system. This system will make sure no water from the garden leaks into the building through wall cracks or crevices. Additionally, the drainage system will have to ensure no water from the garden is dripping down the outside of the building.
If your building has a roof garden, chances are that insurance companies will charge a higher premium than they would to cover the same building without a roof garden. Greater insurance costs represent another way in which a roof garden is often more expensive than a typical garden. Roof gardens may be more dangerous than typical gardens, due to the risk of falling. If you have -- or invite over -- children to your roof garden, ensure the edges of the garden are barricaded so nobody can fall from the roof.
Installing this membrane is a specialist job and can be expensive. Roof garden membranes can become degraded over time or ruptured by screws, nails or the use of garden tools. A ruptured membrane can leak water and soil into the building structure. Renovating or replacing the membrane may necessitate complete removal of the roof garden, which sets you back to square one in terms of garden planning and plant development.
(PDF) Exploring Feasibility of Incorporating Vertical Gardens in Indian Context (researchgate.net)
factors such as constant maintenance difficulties, high cost, lack of knowledge and consciousness in vertical gardens are preparing for the aesthetic purposes and preventing the spread of applications.
If the designer doesn’t adequately plan for their project, they say, the costs might outweigh the benefits.
Maintaining a green wall requires more work and resources than a regular wall, especially if it doesn’t have a self-watering system. You’ll have to manually water the plants, and even with a self-watering system, the plants will need care at some point.
Green walls typically require large amounts of water, which can be unsustainable if supplies are low and the wall isn’t equipped with water recycling equipment. Operating a living wall also requires energy. Producing this energy can have a negative impact on the environment if derived from fossil fuels.
For a green wall to be truly beneficial, you need to use an efficient watering system, put it in the proper place (with ample natural light), and plant vegetation that’s easy to maintain and requires minimal irrigation.
Anyone interested to install a green wall, as well as the architects and engineers in charge of designing them, ought to consider the efficiency of the system in addition to their benefits and aesthetics.
(PDF) Problems and Perspective of Vertical Gardening in the Vladivostok Design (researchgate.net)
It has been established that the main problems of vertical gardening in Vladivostok are: a difficult climate, designers must adapt the existing methods in the world to local climatic conditions; the using of non-acclimatized plants; expensive local planting material; lack of interest in the problem of improving the city’s government structures.
On the Up and Up: Overcoming Green Wall Challenges | Houzz AU
they’re not always that easy to create or maintain at home.
While you have a green wall straight away, it may take some time and experimentation to determine which plants are best to use. Each environment may require a different collection of plants, so take a picture of the site and get some advice from a local nursery.
“Experience has dictated that green walls do not comprise a low-maintenance garden by any stretch. Plants outgrow their pots rather quickly, run out of nutrients in their small containers or quickly die if there’s a fault with the watering system.
Despite the environmental benefits linked to green walls, they haven’t been immune to criticism, preventing them from gaining a solid reputation from a sustainability standpoint. Some argue, for example, that the main advantages that horizontal green spaces bring to cities (like shading or soil drainage) are lost by raising them from the ground – in other words, that cities must rather focus on improving or creating more open spaces.
Peter Massini, natural environment policy-maker, suggests that “green walls are a poor cousin to green roofs,” yet he acknowledges the value of more recent attempts. Others argue that living walls should be considered solely as visual elements, since although they reduce temperatures and insulate buildings, their success is limited by climatic conditions and surrounding circumstances that can harm the structure and plants. Another common critique relates to excessive resource consumption – water, materials and energy –, which could eventually counteract environmental advantages. Of course, this can be avoided or minimized with good design, but some state that there is still a high risk, especially in ambitious cases that stretch over several floors.
Vertical gardens: The good, the bad, the ugly - CSMonitor.com
Google "vertical gardens" and you will come up with tons of DIY ideas and pictures of beautiful living wall, vertical gardens. But as to information on irrigation, plant choices, weather, and site considerations and the cultural requirements of plants? Not so much!
And therein lies the problem. Done correctly by knowledgeable landscapers or gardeners, the effect is awesome. Conceived by people who don’t understand the systems, plant species choices, or proper cultural requirements, the end result is appalling, to say the least.
The Upsides And Downsides Of Vertical Gardening (gardeningknowhow.com)
Moisture and mold. Vertical gardens planted against a brick or masonry wall may drip and harbor moisture that can damage the structure. Similarly, a vertical garden planted above a deck can stain and discolor whatever lies beneath. Vertical gardening is best around concrete or other building materials that are impervious to moisture. Bugs and germs. Vertical gardens can be home to water-borne pathogens that flow from the top of the plant to the lower foliage, then spreading to neighboring plants and soil. Remember that splashing water spreads germs and disease quickly. On the other hand, pathogens spread more slowly in soil, limited by how far moisture seeps or mud splashes. Sun blockers. When it comes to vertical gardening disadvantages, keep in mind that vertical gardens are tall structures that may cast shadows over lower-growing plants. If you choose to grow a vertical garden, consider the needs of plants that may be prevented from receiving adequate sunlight. Consider shade plants, if necessary. Increased maintenance. Vertical gardens generally require more maintenance than plants in the ground. Plants in a vertical garden generally need more water and may require more fertilizer since they are often exposed to the drying effects of wind and sun. Many plants will require regular pruning, and an indoor vertical garden will probably require hand pollination, a rewarding job that can be very labor intensive. Lack of support. Vertical gardens may not be sturdy enough to support large plants such as wisteria vines, melons or tomatoes, although they may work well for sweet peas and other lighter plants. If you want to grow heavy plants, you may need to anchor the set-up to a more substantial supportive structure. This complication is one of the many downsides of vertical gardening.
Don’t jump into vertical gardening until you have a thorough understanding of maintenance requirements, potential problems, and other good reasons not to plant a vertical garden. If your garden lacking a vertical element, you could always consider columnar evergreen trees or tall, bold ornamental grasses.
Growing pains: why some green walls die (architectsjournal.co.uk)
For their part, green wall companies insist living walls should be able to survive forever, and the reason they fail is usually down to poor management. Most firms offer maintenance contracts with lifetime warranties on planting, costing an average of 10 per cent of the wall’s cost. Green wall company Biotecture has contract values that range from £170 to £6,000 a month. But some building managers go looking for cheaper options.
Another ANS green wall, on a shopping mall in Walthamstow, died after a fire damaged the system’s pipework, meaning the wall couldn’t be irrigated. The insurance companies did not pay out to reinstate it.
Irrigation is the most common reason walls do not survive – making up around 90 per cent of failures, says Angus Cunningham, chief executive of green wall manufacturer Scotscape. He adds: ‘Emitters can get blocked, pumps can fail. Signs aren’t spotted until it is too late.’ Another common problem is the incorrect plants being selected at design stage.
The parched walls are a (very public) reminder of how the technology is vulnerable, and once they die the cost to revive them is high. Dead green walls also carry a greater fire risk. A 2013 government report on the fire performance of green walls and roofs states ‘the general consensus is that as long as the green roof or wall is kept moist it is likely to be very resistant to ignition. But as McIntyre says: ‘If the living wall is not correctly and regularly maintained, it is more combustible than a wall that is in full health.’
Green walls’ need for an artificial water source, along with their high maintenance costs, and their status as ‘feature’ items, have led them to be dismissed as expensive ‘greenwash’. As Fionn Stevenson told the AJ in 2009 after the Islington wall failed: ‘Just keeping [a wall] alive creates lorry-loads of embodied energy and pollution. The living wall cannot be sustainable because a basic principle of sustainability is that you do not live beyond your needs.’ However, the technology does seem to have moved on.
Research is also being undertaken by some companies on ‘bioactive façades’ described in a GLA greening report as types of walls with building materials that have surfaces deliberately created to provide opportunities for self-supporting vegetation such as algae and mosses – the aim being to create inexpensive, low-maintenance green walls.
