Millennials who live in the cities find it difficult to relate to stories shared by the older generation. As elders of the family walk down the memory lane and get nostalgic, the current generation draws up a blank. Most of these stories relate to the open areas and green spaces that stretch as far as eyes could see. Cities are breeding grounds for opportunities and growth. However, they are also places where one could only see tall buildings and vehicles. Though people migrate to cities for a better life, it is natural to connect with their roots. One such ingenious idea is the green roof concept. Though this idea has been in use since the Hanging Gardens of Babylon, it has become one of the most sought-after designs in the past two decades.
Green roofs are a layer of vegetation installed on the roof of the building. It can be created on any roof as it brings an array of benefits to the table. Broadly there are two types of green roof systems:
- The intensive green roof system is a layered system that requires a lot of maintenance and care from the owners. It holds the advantage of being the type of system in which one can choose the type of vegetation they want. Space can also be made usable.
- The extensive green roof system is a layered system in which an owner does minimum intervention and lets the vegetation grow like they do in the wilds. The roof space with an extensive green roof system is not for recreational activities. However, they are for non-accessible terrace space.
Though there is a broad level design principle to execute the idea, each green roof is a unique scenario and is dealt with individually. All green roofs would have a layered structure with top vegetation accompanied by a growth medium, filter fabric, and a drainage system. Under the drainage layer, coatings of waterproofing, root repellent, and various insulation layers such as thermal and haze control are installed.
Below are five examples of green roofs highlighting the details of the project:
1. School of Art, Design and Media at NTU, Singapore | Green Roofs
Completed in the year 2006, the ADM inside the NTU campus is one of the most iconic buildings on various fronts. The tapering building has main arcs at 45 degrees that intersect the third arc, forming a sunken courtyard that acts as the central space of the building. Varying between two-five storeys, the glass building accentuates the thoughtfully designed multi-level courtyard and reflects it.
The sloping curved roof of the building is accessed by a series of steps running along the inner edge of the curve. Due to the steep slope of the curves, only 1/6th of the roof can be used for recreational purposes. The crown portion of the curved roofs is used by the students as a collaborative space. The intensive green roof system has two types of grasses, namely Zoysia matrella and Ophiopogon as a vegetative layer.
Irrigated by an automatic sprinkler system that is integrated with a rainwater harvesting system, the green roof of the building is one of the most sustainable features of the building, not only on the water conservation front but the air conditioning loads are also lesser compared to other buildings with a similar footprint.
Due to a thoughtfully designed green roof, the surrounding air is cleaner and cooler and there are no urban heat islands created due to the massive structure. With minimal reflected heat and solar heat gain due to intelligent orientation and blending of the building with the surrounding landscape, the building is a high-performance sustainable building.
The multi-layered green roof structure primarily consists of the top vegetation layer, and four interrelated organic matter that includes crushed volcanic rocks, washed sand, pumice, and a moisture retention layer to moderate the soil conditions throughout the year. The turf slows the surface runoff as well as retains the water on its surface, ensuring the drop in air temperature around the building by evaporative cooling.
The green roof that acts as a natural insulator, coupled with the almond-shaped courtyard reflects the heat and brings in natural light ensuring ample daylighting is achieved.
2. Brooklyn Botanic Garden Visitor Center, Brooklyn
Masterfully embedded into the hillside that existed in the Northeastern corner of the Brooklyn botanic garden, the visitor center is an intelligent addition. Designed by Weiss/Manfredi the LEED Gold-certified glass building consists of a semi-intensive green roof spreading over a 10,000 sq. foot of vegetation that includes grasses, spring bulbs, and perennial wildflowers that are mostly native species.
The leaf-shaped green roof is home to around 40,000 plants that helps in regulating the climate as well as create biological diversity as it was designed as an experimental landscape. To add dynamism to the project, the architects consciously chose non-perennial plants, thus the green roof changes from season to season. In combination with the extensive plantation around the building and the three water gardens, the green roof effortlessly knits the building into the surrounding lush landscape.
Envisioned as an urban oasis the architecture and landscape are so perfectly weaved together that the demarcating line is close to diminishing. Also accessed from the top of the berm bisects the Visitor Center, the stepped ramp connects the entryway to the main area. While the fritted glass façade cuts down the thermal heat gain in the southern side, the northern side is artfully built into an existing berm thus creating thermally insulated spaces.
The living roof ensures less heat gain thus decreasing the heating and cooling requirement and the geo-exchange system lends a sustainable solution for heating and cooling of the interior spaces. The urban surface runoff is drastically decreased by the leaf-shaped vegetated roof that collects the water and manages the stormwater harvesting it efficiently. Acting as a transition element between the urban area and the surrounding landscape, the undulating green roof on the western side was designed with woodland bio infiltration basins.
The roof system is described as type three assembly, it consists of a mineral drainage system under a lightweight growing medium. The root permeable separation fabric ensures that the fine-grained growing layer doesn’t blend in with the granular layer that absorbs the moisture to regulate the runoff. An extensive amount of roof stabilization was done to more than half of the area of the gable roof by securing banana cleats to a geogrid net.
Due to a variety of water-loving plants around 200,000 gallons of water is harvested from the building each year. As a result of the biodiversity of the plants that are housed on the green roof, a variety of birds and pollinators set nests in the vicinity.
3. Meera Sky Garden House, Singapore
Located on the island of Sentosa, the 9150 Sq.foot house was designed with the sole intention of reducing the dependency on mechanical ventilation. Due to the closely spaced building the sides of the building have a solid wall construction, while on the front side the plan is stepped back at each level creating terraces on each level. The green roof on each floor creates an overhang that shades the lower floor, minimising the solar heat gain from that large expanse of the façade glazing that brings in ample natural light.
Conceptualised as a structure that enhances the quality of life and brings one closer to nature, the entire building has sustainability integrated at multiple levels. The terrace gardens on each floor help in water retention and regulate the runoff of the rainwater, thus conserving water and replenishing the water table. The micro-climate of the three-storey structure is regulated by the multi-level terrace gardens that also serve as family space for the occupants.
The curved roof of the top floor accentuated the building making it stand out amongst the other buildings of the neighborhood. The main ideology behind the terraces of each level was to visually as well as functionally induce a feeling of living in a countryside house with surrounding sprawling lawn areas on each level that connected with the landscape and sea at each level.
The three-storied structure has garden space on first- and second-floor levels as well as the curved roof that acts as a crown of the project. These gardens are home to a variety of
A lush grass lawn creates a blanket over the entire area of the terraces, making them accessible for the user. The intensive green roof system of the terrace includes a fine growth medium layer under which an extensively planned drainage system is installed to collect the runoff.
As the water retention capacity of the roof is high, the terrace helps in cooling the air by evaporative cooling, and the cool air is circulated through cross ventilation in the smartly planned spaces. The trees purify the air and cut down the noise disturbance of the touristy island, creating serene living spaces.
4. ACROS Fukuoka Prefectural International Hall, Japan
Built in the center of the Fukuoka city’s park, the building artfully balanced the demand of a developer for maximum utilisation of FSI and the environment and social need for open green spaces that encourage interaction and growth of the culture. Due to limited space availability in the urban area, the new government building had to be located in a park.
The imposing multi-storied building’s design inspired by the hanging gardens of Babylon was designed to step back the layout at each level creating terraces on the front portion of the building. The 15 levels of terraces house around 1,00,000 Sq. feet of landscape area, home to a multitude of native species.
The living roofs brimming with flowering and non-flowering plants, herbs, trees, and shrubs create a canopy visually transforming the glass building into a giant stepped garden from a utopian region. Architect Emilio Ambasz proved that ‘where there is will, there is a way’ and executed every person’s fantasy to construct a building without disrupting nature.
The iconic building’s landscape was envisaged as a mountain of nature and the vegetation changed with the passing of each season. The accessible terraces on fourteen floors house community spaces for meditation and congregation while the terrace on the 15th floor was designed as a glorious belvedere that bestowed a panoramic view of the bay area and mountains. The intensive green roof system adopted for the terraces was separately designed for each floor based on the type of vegetation the terrace housed.
The growing media had various combinations and the depth of it ranged from 1′ to 2′. The building that was planned as a home for 37,000 plants from around 76 native species has now developed into 50,000 plants from a colossal number of 120 species, proving that nature has taken over the building. A study conducted in 2001 proved that the microclimate inside and around the building had a huge temperature difference of 15 degrees.
Due to the thick foliage on the building, the surrounding air is purified and the ambient noises are filtered, creating a peaceful reprieve amid the hustle and bustle of the city. The rainwater harvested from the building ensures it has been recharging the groundwater thus saving the city from water shortage issues.
5. The Vancouver convention centre, Vancouver | Green Roofs
Located on the waterfront of Canada’s most culturally vibrant city Vancouver, the convention center was envisaged as a building that harmoniously amalgamates built and open spaces, creating an ecologically responsible architecture. The LEED Canada-certified building was envisaged as a celebration of people and place and aimed at setting a benchmark for sustainable buildings. One of the most iconic concepts that were incorporated in the building is the six acres green roof that is touted as the largest living roof in Canada.
Abode to 40,000 native plant species and grasses, the intensive green roof system has about 1′ deep growing media that has a sustainable irrigated system integrated with waterproofing and root repellent media layer. The system was designed with a metal deck, Densdeck, 4″ insulation media, and a filter cloth. The non-accessible green roof is also home to 240,000 bees in four colonies, whose honey is harvested for the restaurant.
The living roof was designed to function as an insulator that cuts as much as 95% of the solar heat gain in summers and has a solar retention capacity of 26% in winters, mediating the microclimate in the area, thus reducing the heating and cooling loads of the building.
The slope ranging from 3% to 56% has ILD’S patented EFVM (Electric Field Vector Mapping) system. The slope of the roof built on natural topography creates an ecological and visual connection between Stanley Park and the North Shore Mountains.
Due to the sloping profile of the roof, a natural drainage system is ensured, additionally, it also ensures an innate seed migration pattern. The building has an integrated stormwater drainage system that harvests the surface runoff that is slowed down and retained by the green roof and integrates it with the waterfront. The wastewater produced by the building is treated and reused for the landscape, conserving potable water.
The glass skin brings in diffused daylight while diminishing the demarcation between the indoor and outdoor spaces. Since the roof is non-accessible to the public it has developed into a natural habitat for various migrating and native species alike. Though it is inaccessible for people, viewpoints from various locations are designed to enjoy the beauty of the natural habitat in the centre of a busy city.
Urban areas are perceived as the place for buildings while green areas are taken as spaces that belong in country/rural sides. While the world is rushing towards growth in lighting speed architects hold the responsibility of balancing development and environment. Sustainability in buildings is a concept that has been getting the attention of designers in the past two decades but sustainable development is a concept that has to be well thought of by architects.
“The good building is not one that hurts the landscape, but one which makes the landscape more beautiful than it was before the building was built.” – Frank Lloyd Wright
The green roof is a very perceptive idea that ensures one could give the space utilized for building a structure back to the environment. Though it has its own set of challenges and additional costs for designing and integration, it helps in the reduction of operational costs of building, adds aesthetic value to it, and also creates a space for repose. It helps a person in establishing a connection with nature and would help in the global warming crisis.
