Buildings are responsible for 40% of the world’s greenhouse gas emissions and the construction industry has a substantial impact on the environment. Strong policies in regards to energy-efficiency and the managing of water resources in this industry need to be implemented to mitigate climate change.
Marloes Reinink from Solid Green Consulting recently talked about the impact of buildings on the environment in her presentation during the Walls & Roofs Architectural Day. She said buildings utilise one third of the world’s resources.
Because of these alarming statistics, designing a green building on sustainability principles becomes very important. She defined a green building as a building which is energy-efficient, resource-efficient and environmentally responsible, and incorporates design, construction and operational practices that significantly reduce or eliminate its negative impact on the environment and its occupants.
What makes a green building?
One of the key decisions to be made when designing a green building is to choose a proper site location. There are various factors to consider in this process that will minimise the impact of a building on the environment. “It is all about the location,” Reinink said. “Choosing a brownfield site that can be re-used is a better option than developing a site that has a high ecological sensitivity,” she added. According to her, one should also use the incorporation of transit nodes for optimal use of traffic networks and proximity to jobs as guiding factors in choosing a site.
Reducing energy use through passive designs
Reinink said one way of implementing energy-efficiency in a building is to use passive design. Passive design is not an attachment or supplement to architectural design, but a design process that needs to be integrated. Although it is mostly applied to new buildings, it has also been used for refurbishments. In passive solar building design, windows, walls and floors are made to collect, store and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design or climatic design because, unlike active solar heating systems, it doesn’t involve the use of mechanical and electrical devices.
“The key to designing a passive solar building is to best take advantage of the local climate,” she added. “Elements to be considered include window placement and glazing type, thermal insulation, thermal mass and shading. Passive solar design techniques can be applied most easily to new buildings, but existing buildings can be adapted or retrofitted.” Using daylight optimally can also up the energy-efficiency of a building.
According to Reinink, passive solar design can reduce buildings’ heating requirements by 20% to 40%. “Proper shading can reduce the cooling requirements of a building by the same percentages,” she adds. She also mentioned that natural ventilation can replace 60% of the ventilation requirements and that the “smart” use of daylight can replace artificial lighting by 35% to 75%.
Incorporating an effective daylight and shading strategy by using light shelves can improve the way in which daylight is harnessed. One can use large windows on the north and south facades of a building to let daylight in and manage shading by using large overhangs to keep the sun out. She said one could also include a mixed mode ventilation system and motion and daylight sensors to control the artificial lighting of a building to optimally manage energy resources.
Warren Gray, a sustainability design engineer at Solid Green Consulting, talked about daylight harvesting during his presentation at the Walls & Roofs Architecture Day. According to him, “Better daylit spaces can be achieved by quantifying natural light levels in the design phase, something that is not typically done at present.” He also highlighted that building geometry plays a large role in self-shading and other passive heating and cooling factors As such, it can have a significant impact on heating and cooling energy and should be appraised for energy performance.”
Gray said architects should apply out-of-the-box thinking to find a solution in managing human comfort and the use of energy in achieving it. “It all comes to using the best computer design tools available during the design phase. The obvious choice is not always the best solution in creating a building that would suit the needs of the client and protect the environment.” According to him, it is important to consult all engineers in the design process to understand and implement energy-efficiency optimally.
Reinink explained that buildings consume 12% of the world’s water resources. She says that one way to manage the water consumption of a building is to install water efficient fixtures and fittings. In addition to that project should look at the use of rainwater harvesting and recycling of grey (wash hand basin and shower water) or black (toilets and kitchen water) water and reuse in the building. If landscaping is part of a development, this is likely to be the largest water consumer, and careful attention should be given to landscape design in terms of the plant selection, low water irrigation systems, and use of recycled water (rainwater, grey or black) water for irrigation purposes.
Creating healthy spaces
“Air quality in buildings typically contains five times more pollutants than outdoor air,” Reinink says. According to her, the ultimate goal in designing a green building is to create healthy spaces that benefit the occupants of a building. To achieve this, architects need to ensure occupant comfort and allow for enough fresh air to be present in a building. She further suggested that natural ventilation can be used as a tool to create healthy spaces. “It can also contribute towards the regulation of air quality, creating beautiful views and managing indoor pollution,” she said. According to her, designing a building for the benefit of the occupants will lead to improved health and create a productive environment.
Adding a green roof to a building is another interesting way to incorporate a “green element of design” into a building. It allows the client to utilise unused space. A green roof means a floral or vegetable garden. A green roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. These roofs should also include additional layers such as a drainage layer and irrigation systems depending on the type of green roof.
Green roofs can be categorised as intensive, semi-intensive or heavy intensive, depending on the depth of planting medium designed for.
Lesley Cicero, a regional specifications consultant at BASF, says that a light-intensive green roof is 90 to 170kg/m². According to her such a green roof requires minimal maintenance, due to its shallow soil depth and occasional access. Cicero says only selective plants that can flourish in a shallow growing medium should be used to create this type of green roof.
Cicero pointed out that heavy intensive green roofs are about 350 to 1 000 kg/m². She says heavy intensive green roofs need more maintenance as it has greater soil depth. “These green roofs are commonly turned into gardens and more accessible owing to its garden status,” she adds. “It provides for greater soil depth as plants like trees, shrubs and bushes are generally planted.”
Sustainability in roofing materials
Sally Stromnes, marketing manager of Safintra Roofing and Steel, says that as South Africa embraces sustainable building practices, roofing systems should provide the owner with optimum levels of performance and lifespan. Sustainability is defined as having environmental, social and economic dimensions. For steel roofing, sustainability is associated with using less raw materials and delivering a longer lifespan for the roof, whilst also being environmentally efficient in a roofing application.
Steel roofing has sustainability credentials that make it increasingly attractive for discerning users and specifiers. Stromnes added: “Steel roofing, particularly Aluminium-Zinc coated roofing, provides a substantially longer lifespan than alternative coated steel. An extended service life means it uses less raw material in the longer run.” Steel roofing also has the benefit of being able to accommodate panels and water harvesting systems without compromising the weather-proof performance of the roof.
Steel itself is inherently eco-friendly, as Stromnes explained. “Not only is it the most recycled material in the world. Steel also has a low thermal mass, which means that it requires very little energy to change its temperature. So while it may heat up quickly, it also cools down quickly.” These properties make a steel-roofed building more comfortable to occupy in all weather extremes, reducing the energy needed for cooling in summer and heating in winter“, Stromnes said.
She explained that SANS 10400XA legislation would drive innovation in roofing design and installation, particularly insulation. The structural properties of steel roofing make it highly accommodating to insulation, and the ease of re-roofing or retrofit of thermal insulation in steel roofing structures will be an increasingly important decision driver for architects and building owners. She stressed that the investment in roofing a structure is substantial, and such a critical part of the total building’s durability and service life, that owners and investors are advised to ensure that every individual component in the roofing “system” has the quality and therefore the longevity to perform as they should. Manufacturers and suppliers should be able to provide warranties which ensure that the investment performs as expected and for the duration of its promised service life.
Roof systems and insulation requirements
Dion Marsh from Ashgrid says that since the much anticipated energy-efficiency legislation was passed, the long-span roof sheeting industry has been faced with a number of serious challenges. According to him, the new legislation effectively requires far deeper sections of insulation to be installed to the roof space in order to achieve the prescribed R-values. “For insulation to perform to its optimum levels, it is imperative that a continuous layer is installed with minimal thermal bridging. The ideal location for this continuous layer of insulation in the roof space is over purlin.”
He further explains that there are a number of problems associated with securing both concealed and pierced fix roof sheeting directly over bulk or rigid insulation. “The industry has until recently tried to overcome these risks by using U-shaped stirrups which are pressed or cut into the insulation to provide additional support to the fixings and the roof sheet.” Marsh says that these stirrups or spacers are laborious to install, do little to reduce the stress on the fasteners and do not adequately support the span of the roof sheeting. “Roofs are easily damaged by subsequent foot traffic. The performance of the roof covering remains compromised.” He says that another method employed is the installation of a second row of timber purlins. “These timber purlins are fixed to the first row of purlins whilst sandwiching the insulation between them.”
According to Marsh, not only does this result in excessive compression of the insulation and thermal bridging, but it also results in the timber spacer purlin being out of alignment due to varying compression rates. “This again compromises the performance of the roof covering,” he adds. Marsh explains that one could also use a roof spacer system that will compensate for the insulation used in a project. “A roof spacer system is simply a second row of engineered purlins which allows for the creation of a defined cavity or roof space to accommodate insulation without compromising on the performance of the complete roof system.”
He says roof spacer systems should be versatile and must provide the professional team with the freedom to employ a combination of methods in order to achieve high levels of thermal and acoustic performance in a cost-effective way.
Incentives to go the green route
The SANS 10400 energy-efficiency standards and the new SANS 204 building regulations are not only an incentive, but a requirement that drives transformation in the building industry. Reinink said the Green Star rating system of buildings is a market-driven initiative that inspires architects and contractors to adapt to market changes.
Reinink says the Green Star rating system is a tool that architects can use to guide them in the process. “The Green Star rating system evaluates environmental performance, sets a framework with benchmarks in place and recognises environmental leadership.” She added that the rating system promotes an integrative and holistic approach to designing a building. There are current tools available for office parks, retail and multi-unit residential projects as well as a pilot public and education buildings (PEB). The PEB rating tool assesses the environmental attributes of new or significantly refurbished public and education building developments.
Reinink said that in the future there will also be tools available for the interior design of a building, mixed uses and existing buildings as well as communities. For a building to qualify for a Green Star rating, integrated design is one of the most important requirements. “Architects have to work as a team with the other professionals to increase green performance of a building that can complement its aesthetic appeal.”
Living in green cities
Reinink said: “In the end the goal is to create greener cities where the whole is greener rather than the sum of its parts.” She says a green city is an urban environment with compact neighbourhoods, connectedness to surroundings, as well as walkable streets, places for social interaction and efficient public transport infrastructure. “Of course green buildings should also be part of the mix.”
One way to inspire urban dwellers to take a walk rather than using a vehicle is to use the function of trees optimally. “A tree line in a street spatially divides the street and pedestrians, protecting those who want to go for a stroll.” She says that it also filters the sunlight, creating comfortable temperatures and reducing urban heat. “Trees also soften building facades,” she explained.
Green buildings in South Africa: Nedbank Menlyn Maine
“Menlyn Maine is proud to announce that the Nedbank Falcon Building has been completed on time and on budget,” says the development director, Justin Bowen. “We are incredibly proud of how the building has turned out and hope that Nedbank will enjoy their new home.” The building was awarded with a four-star Green Building rating.
According to the GBCSA, the Nedbank Menlyn Maine Falcon Building will be the new home of the Nedbank regional head office. It is the first building that was developed in the Menlyn Maine precinct, east of Pretoria Central. “The Menlyn Maine precinct is designed as a mixed-use development. It is envisaged that the precinct will include retail and residential buildings, as well as other office developments.”
Mathieu du Plooy, managing director of WSP Africa, says they are proud of achieving yet another certification for Nedbank. WSP Group is the structural engineers and sustainable design consultants for the project. The Green Star rating was achieved by incorporating various sustainability standards.
Indoor environment quality
The fresh air intake in the building is 150% more than required by SANS 10400 standards. According to WSP Africa, it was designed for daylight penetration, with at least 30% of the office areas having a daylight factor of 2%. “The façade design will minimise discomfort of glare through the use of fixed shading devices for a majority of the working hours, with high frequency ballasts installed in fluorescent luminaries in the office area,” WSP Africa says.
The company further explains that material with reduced volatile organic compounds (VOC) was used for the office interior paint, adhesives and sealants to meet maximum Green Star South Africa Office v1 nominated levels. The composite wood products will have reduced formaldehyde levels. The building is non-smoking, with no designated smoking areas inside.
WSP Africa added that the HVAC system of the building consists of four pipe-fan coil units for heating and cooling with thermal ice storage achieving 45% energy improvement over the SANS204 national building. “The lighting achieves energy usage of 1,76 W/m² per 100 Lux and the lighting design will allow for flexible light switching. The lighting zones are designed in a way not to exceed 100m² in offices. Motion sensors and daylight sensors were also installed,” the company says.
A dedicated storage area will be provided on site for the separation and collection of paper, glass, plastics, metals, used compact fluorescent light bulbs and other materials by all the building occupants. “The steel used in the building will have a minimum of 60% post-consumer recycled content, with concrete bearing a minimum fly-ash content of 30%,” WSP Africa says. “PVC usage has been reduced and replaced with other materials like HDPE for the stormwater and plumbing installations.”
Mayfair on the Lake
The design of the Mayfair on the Lake project is governed by environmentally sustainable principles epitomising the owner’s commitment to environmental sustainability. The project is being constructed to achieve four-star Green Star SA Office v1 ratings. Mayfair on the Lake will deliver highly efficient usable floor area ratios with an economical facade, whilst keeping a human scale and a high level of detail.
Mayfair on the Lake is an L-shaped five-storey office building which responds to the urban environment created as part of the new-urbanism initiative in the area. It is situated in the heart of the Umhlanga New Town Centre, overlooking the Gateway Shopping Centre. Construction was coming to a close in April 2012.
The ground floor will incorporate 879m² of retail space and above, four floors of office space totaling 5 440m², available in various sizes and configurations. Premium grade finishes will be used throughout and a number of green features are being introduced that will provide significant benefits to tenants. There are two levels of basement parking as well as adequate visitors’ parking.
Some of the green features incorporated in the Mayfair project are innovative architectural design with specific reference to sun control and the reduction of heat loads within the building. It also includes indoor environment quality, a reduction in ambient noise levels, an energy-efficient lighting system as well as the use of construction materials from renewable sources and an indigenous water-free landscape.
South Africa still has a long way to go to transition into a low carbon economy. The construction industry can play a vital role in facilitating this process. Industry leaders currently have the opportunity to step up and set new standards in regards to sustainability. Architects, specifiers and developers need to fuel the demand for sustainable solutions in the building industry to create a foundation for change.
Full acknowledgement and thanks are given to the Green Building Council of South Africa, Solid Green, BASF, Safintra and Ashgrid for the information given to write this article.
– Written by Nichelle Lemmer