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Net Zero Waste in Construction

By Gordon Brown

According to the World Green Building Council the construction sector accounts for up to 40% of waste in landfill sites worldwide, and while this figure may be lower in South Africa construction remains a significant contributor to landfill content. The National Waste Information Baseline Report (DEA2012) indicates that the construction sector is responsible for 8% of all waste generated, although it is unclear whether this number includes the waste from product suppliers during production, which is significant. Importantly this statistic also excludes the ongoing operational waste generated in all occupied buildings, and so is understated.

Construction waste is made up of aggregates (concrete, stones, bricks) and soils, wood, metals, glass, biodegradable waste, plastic, insulation and gypsum based materials, paper and cardboard, a very high percentage of which are reusable or recyclable if separated at source. Currently 16% of construction waste is recycled in South Africa (NWIBR).

Trends and forces for change

The green building movement is being spearheaded by the CSIR and the Green Building Council of South Africa, the latter having set up rating tools that award points for, amongst other green building aspects, resource efficiency for designs which reduce waste.

Best Practice

Construction waste emanates due in some part to inconsiderate design, construction, maintenance, renovation and demolition, as well as supplier considerations such as packaging. Intelligent design and best practices during each phase can significantly reduce waste.

Design

Architects and engineers have a very significant opportunity to affect the waste generated through the life cycle of a building by determining the method of construction and the materials specified. From simple strategies like utilising building rubble onsite as fill for instance, or reusing items from demolished buildings such as wooden window frames, by specifying materials with recycled content, and adopting strategies and building methods geared to dismantling and designed for deconstruction – design affects everything, and with careful planning and consideration given to waste and reusing materials at concept stage, much waste to landfill can be avoided. An example of this is modular construction.

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It is also very important at design stage to consider how the building is going to manage operational waste while the building is occupied – sufficient space will be required for recycling storage and sorting, as well as the access to various floors and of course for collection.

Construction

At a waste management level, there are a number of best practices to ensure maximum recyclability of materials on site:

  • Make this consideration a key performance criterion when appointing contractors
  • Set targets for % of waste not to go to landfill (refer to Green Star SA for achievable best practice)
  • Have a waste management plan drawn up according to best practice prior to beginning the project(ie. Part of the tender/brief document)
  • Have correctly marked skips for certain waste streams
  • Ensure that the correct paper work is filed for all items removed from site
  • Safe disposal tickets for hazardous waste must be kept

Keep a monthly and overall project reports of all waste and at the conclusion of the project –confirm whether targets are being achieved

There are many great examples of achieving excellent standards in construction waste management, one of these was the first Green Star SA certified project in South Africa, the Nedbank Phase II building in Sandton – in 2008 the contractor was initially concerned about the high standards set within Green Star SA for waste diverted from landfill (30, 50, or 70% of construction waste). By the end of the project, with the good waste management programme they employed, they were surprised at the incredible success – they were able to divert over 90% of their construction waste from landfill. This is a significant achievement, and is replicable across all construction projects by implementing good waste management programmes.

Product and Material Suppliers suppliers have huge potential to reduce the amount of waste going to landfill. Many suppliers could provide their materials to site in a way that requires less or no ‘packaging’, or packaging that is recyclable, and also ensure that their contract with the construction contractors is such that their packaging is returned to them directly for recycling or reuse. ‘Packaging’ is a significant waste source. (Packaging refers to anything that is not the actual material that will be used and left installed on site.) Besides the ‘packaging’ referred to, the product suppliers are also responsible for a significant amount of waste at their own factory or storage houses – the contractors and design team can have a significant influence on the downstream waste impacts by contracting only with suppliers that minimise their waste production and maximise recycling and reuse of waste.

The building in operation

During the course of a buildings life it will require multiple new light bulbs, new carpets and flooring, painting, filling, stripping, windows due to breakages etc. Good building managers and operators can make the necessary effort to separate materials.

The Green Star SA rating tools will reward designers for making provision for separation operations within the utilities area of the building, and building maintenance would utilise these facilities for its waste streams. It is important to have both the space designed to store and sort the waste for collection, but also to have waste management policies in place for the ongoing operation while the building is occupied.

Market forces

As the market places a greater value on sustainability, products with recyclable content become more sought after. Masonry bricks made from crushed aggregates, tiles made from recycled plastics, are just two examples of products gaining traction.

On the waste disposal side, costs are rising but it remains relatively cheap to dispose of construction waste to landfill, cheaper in fact than general waste disposal which costs R272.00 per ton.

As costs increase so too does illegal dumping, which poses an environmental problem, and municipalities need to consider increasing the penalties imposed on transgressors and to find ways of policing illegal dumping more effectively. Perhaps funds from increased charges for legal dumping can be directed in part to policing illegal dumping.

The construction sector has a massive impact and a commensurate opportunity to effect positive and meaningful change. Through a combination of product design and innovation, building design and methods, and through best practice waste management on site the sector can radically reduce the amount of waste created and significantly improve on the rate of recycling.

Source: Green Building Handbook Volume 6


 

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Optimising Daylight in South Africa: A case study

Light is of decisive importance in experiencing architecture. The same room can be made to give very different spatial impressions by a simple expedient of changing the size and locations of its openings. Moving a window from the middle of a wall to a corner will utterly transform the entire character of the room. To most people a good light means only much light. If we do not see a thing well enough we simply demand more light. And very often we find that it does not help because the quantity of light is not nearly as important as its quality. (Rasmussen, 1964)

At the moment lighting accounts for around 35% of the energy used within non-residential buildings and between 0% and 28%1 in residential buildings. Electricity usage (%) in the residential sector for high/ middle income residences consume typically 5% for fluorescent and 12% for incandescent types of lighting. (UNEP, 2009). Designers are encouraged to use natural daylight in their designs to reduce the energy used (SANS 204-2, 2008).

The use of daylight to supplement or as a substitute for electric light in the window zones of interiors with side windows or over the entire area of spaces with skylights can save lighting energy. This saving should be balanced against the energy required to compensate for heat gains and losses through the daylight openings. During times of low external temperatures more heating and during times of high external temperatures and sunshine more cooling of the interior will be required in order to maintain a constant internal air temperature. The use of daylight therefore will only be energy effective and cost-effective if the savings on lighting exceed the extra expenditure for climate control (SANS 10114-1, 2005)

Uses of Daylight

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Natural daylight is a very important and interesting source of lighting in buildings. Natural daylight can inter alia be used for functional1, decorative2 and artistic3 purposes. In the SANS 204-2 and 10114-1 norms the emphasis is mostly on functional uses. The light levels, power and energy usage for the building is determined in accordance with a lookup table 14 (SANS 204-2, 2008).This table describes the recommended light levels, power and energy for various classes of buildings. The light levels range from 50 lx for entertainment and public assembly to 700 lx for high risk industrial type of spaces.

The developments in electric lighting have not eliminated a widespread preference for daylight in buildings, wherever practicable. The reliance on daylight is greater in homes, offices, schools and patient areas in hospitals than in factories and shops.

The factors listed below will be different for different types of interior, different methods of daylight admission and for different climates (See Table 6.2). Recommendations regarding daylight should inter alia allow for the following factors (SANS 10114-1, 2005): Levels and uniformity. Daylight provides variability and, when it enters through side windows, creates a specific modeling and luminance distribution in the interior. It therefore contributes to visual satisfaction. The quantity of daylight is usually specified by the daylight factor, both with regard to illuminance and uniformity. In interiors with side windows, the available daylight decreases rapidly with distance from the windows. In many cases such as living rooms and small offices this non uniformity is acceptable and even appreciated. In other cases, supplementary electric lighting is required. Roof lights (skylights) can provide ample and highly uniform daylighting, but should be carefully designed to avoid solar overheating and glare.

• External view. Where natural light is used throughout the day for reasons of convenience and economy, an additional advantage is the view of the outside environment. However this is not always possible in large industrial or commercial buildings. The best position, shape and dimensions of the windows will depend on the nature of the outside environment. It also depends on the building design and will take into account architectural, lighting, visual, thermal and acoustic considerations.

Glare from the sun or sky. Daylight can produce sky glare and can adversely affect the comfort in the interior. Direct sunlight is desirable for various types of buildings, such as homes in moderate climates, but should generally be avoided in work areas. Means to avoid direct sun irradiation are appropriate orientation of windows and skylights, the use of various types of curtains or blinds and the use of louvres or screens. The latter are also effective in reducing sky glare and are particularly important on the upper floors of high-rise buildings where large parts of the sky might be visible. Small windows have an effect on the sky glare only to the extent that they prevent parts of bright skies or bright opposite facades or buildings from being seen. When appreciable areas of a bright sky remain in the field of view some glare such as discomfort5 glare or disability6 glare should be expected. Therefore, even with small glass areas, work areas directly facing windows should be avoided. If this is not possible, some means should be provided to reduce possible sky glare. Other techniques to reduce window glare are:

• The use of external or internal devices, such as louvres.
• Deep splayed reveals on the side of the windows, finished with a high reflectance surface and

with the same finish applied to any frames and glazing bars.
• The use of tinted low transmission glazing.
• Arranging for light in the interior to fall on the wall area adjacent to the windows, either from roof lights or from specially located luminaires.

Heat gains and losses. The heat gain through windows might require cooling of the interior during

the warm season, but might reduce heating costs during the cold season. However, heat losses through the window during the cold season can offset the savings and can increase heating costs. The use of daylight as an illuminant can save energy used for electric lighting, but this should be balanced against the energy required to compensate for the heat gains and heat losses through the glazing. Means to avoid excessive solar heat are:

  • Appropriate orientation of glazing.
  • Reduction of areas of glazing.
  • Use of an appropriate daylight system (Table 6.2)
  • Use of heat-reflecting or heat-absorbing glass or coated glass.

The International Energy Agency (IEA, 2000) recognizes a wide range of innovative daylight strategies and systems. Some are rarely used in South Africa. The IEA recognizes two basic types of daylight system i.e. daylighting systems with Shading and daylighting systems without shading. The latter type consists of four subdivisions:

• Diffuse light-guiding systems
• Direct light-guiding systems
• Light-scattering or diffusing Systems • Light transport systems

Gallery below provides some examples of the various types.

Luminance and iLLuminance

Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/ m2). Luminance is often used to characterize emission or reflection from flat diffuse surfaces. The luminance indicates how much luminous power will be detected by an eye looking at the surface from a particular angle of view. Luminance is thus an indicator of how bright the surface will appear. In this case, the solid angle of interest is the solid angle subtended by the eye’s pupil.

For a perfectly diffusing surface, the luminance can be calculated in accordance with the following formula (SANS 10114-1, 2005):

where

L is the luminance, candelas per square metre; E is the illuminance, in lux;
r is the reflection factor.

For example, if a matt surface that has a reflection factor of 0.5 is exposed to an illuminance of 200 lx, the luminance is

cd/m2

Illuminance is a photometric measure of the total luminous flux incident on a surface per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with the human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance.

In the SI system these are measured in lux (lx). lluminance was formerly often called brightness, but this leads to confusion with other uses of the word. “Brightness” should never be used for quantitative description, but only for nonquantitative references to physiological sensations and perceptions of light.

4. Daylight factor
The daylight factor is the ratio of internal light level to external light level and is defined as:

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where:

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For example, if a matt surface that has a reflection factor of 0.5 is exposed to an illuminance of 200 lx, the luminance is

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Illuminance is a photometric measure of the total luminous flux incident on a surface per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with the human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance.

In the SI system these are measured in lux (lx). lluminance was formerly often called brightness, but this leads to confusion with other uses of the word. “Brightness” should never be used for quantitative description, but only for nonquantitative references to physiological sensations and perceptions of light.

4. Daylight factor
The daylight factor is the ratio of internal light level to external light level and is defined as:

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where:

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There are basically three paths (daylight factor components) along which light can reach a point inside a room, i.e. through a glazed window, rooflight or aperture as follows:
• The sky component (SC) that is direct light from part of the sky or sun at the point considered.
• The externally reflected component (ERC) that is light reflected from an exterior surface and then

reaching the internal point measured.
• The internally reflected component (IRC) that is light entering through the window but reaching

the point only after reflection from an internal surface.

The sum of the three components gives the illuminance level in lux at the point measured. The daylight factor only gives the proportion of daylight from outside that reaches the interior of the building and does not indicate the absolute level of illumination that will occur.

To calculate daylight factors requires complex repetition of calculations. It is normally undertaken by a software product such as Radiance. This is a suite of tools for performing lighting simulation which includes a renderer as well as other tools for measuring the simulated light levels. It uses ray tracing to perform all lighting calculations. The design day used for daylight factors is based upon the standard Commission Internationale de l’Eclairage (CIE) overcast sky for 21 September at 12h00 and where the ground ambient light level is 11921 lux. Since the CIE standard overcast sky assumes no orientation effects, the estimates of the daylight contribution can be wrong. To correct for this, orientation factors have been derived to be applied to the daylight factors. More recently the CIE has derived a standard based on the spatial distribution of daylight, i.e. the CIE Standard General Sky (CIE, 2002).

Rooms with a DF of 2% are considered daylit. However a room is only considered as well daylit when the DF is above 5%.

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Case study

The following is an example of how a designer might approach a design analysis to optimize daylight in a building. The first step is to determine the solar angles at different times of the year accurately. With the advent of Google Earth it has become much easier to determine these accurately. This is the basis for the calculation of solar angles.

Read the entire article in the Green Building Handbook Volume 4 on pg 114 here. Or sign-up to download the digital version of the handbooks here.


 

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Mauritius Commercial Bank: Ebene Building

By: Jean Francois Koenig, Architect

The Mauritius Commercial Bank, the oldest bank in Mauritius and the Indian Ocean islands founded in 1878 and based in the capital city Port Louis, February 2006 saw me design offices and training facilities in Ebene, in the centre of the island, which decentralised them from Port Louis for the first time in history.

Their brief came with instructions to keep it simple and inexpensive. They got something different that went far beyond the brief. The building reinvented the client’s way of working and thinking about the workplace and the environment.

To put it in context, it started at a time before many Green Building Councils around the world had been formed and it became the first building in the southern hemisphere to obtain a British Research Establishment Environmental Assessment Method (BREEAM) certificate. The building also became the first Mauritian work of architecture to represent with four others the best of African architecture at the International Union of Architects (UIA) World Congress inTokyo 2011, a triennial event and with it, I was elected as one of the ‘100 Architects of the World 2012’ in a competition organised by the Union of International Architects (UIA) and the Korean Institute of Architects (KIA).

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It has become so popular with the client that they all want to work there and sometimes board meetings traditionally held in Port Louis have been switched from head office to the new building. Energy savings begin with a well insulated building and optimum orientation. The concrete shell is insulated with 50mm rigid polystyrene, an air gap of 350mm and an 8mm thick honeycombed aluminium external skin. The portholes in the glass rings all around the ellipse are double glazed and with the air gap of the outer reflective glass skin creates a triple glazing solution. The two glass facades of the ellipse are true north-south with sunscreens whose projection depths were determined by sun path analyses. They are 1.8m on the north face and shallower at 1.2m on the south to prevent direct sunlight hitting the full height double glazing during working hours from 8.30am to 4.30pm. During this period, the blinds remain up to allow maximum glare free daylight to enter the 22m deep floor plate eliminating the need for artificial lighting entirely. Low angled early morning and late afternoon sun is controlled by perforated blinds which drop down automatically from sun sensors relayed to the computerised building management system.

The building is the expression of an abstract geometric shape in the form of a pure ellipse. It is held aloft on four pillars. Born from the need to accommodate both auditoria and offices, it is the architectural synthesis of these two different requirements fused into one single shape. It is an example that Islands care about, and can make a leading contribution to global sustainability even though they have a low carbon footprint and insignificant impact on climate change.

The orientation of the elliptical glass facades is true North-South. The blank curved East and West ends are well insulated and the portholes are triple glazed. The photovoltaic cell farm contributes to over one third of the total energy needs at peak with clean solar power.

The Board Room on the top floor shows the expressed steel structure, natural light entering from the roof and the sides, and the ample space provided for the long table as well as two rows of plants under the glass rings.

Plant rooms, traditionally situated on the roofs of buildings, are situated on lower levels for ease of access and maintenance. This liberates the roof allowing large spans and column free spaces on the upper floors facilitating internal planning.

Screen Shot 2015-01-28 at 2.07.17 PMFull height double glazing allows in a maximum amount of natural daylight. The depth of sunscreens, deeper on the north facade and shallower on the south facade are determined from the study of sun paths. Sensor controlled perforated venetian blinds are activated automatically to control glare. To eliminate interference from external noise from the nearby motorway the glass walls of the auditoriums are triple glazed.

There are no suspended ceilings in the building, not even in the acoustically engineered auditoriums. The underside of the concrete slabs are kept bare and painted white.

Underfloor cooling passes through a stabilised air plenum without ducts optimising flexibility. No ceilings allow cold energy stored within the thermal mass of the structure to radiate directly into the floor below keeping ambient temperature down and diminishing cooling loads.

The ‘all air’ air conditioning uses ‘free cooling’ in winter months. Three large thermal storage tanks insulated and clad in polished stainless steel store energy to further reduce cooling loads.

Night time illumination accentuates the shape of the building whereby its beauty, like the soul, comes from within. Five glass rings encircle the building accentuating the purity of its geometry. Portholes enhance the air and space ship quality of the architecture gives the sense that the building is ‘landed’ on its base.

Access to the plant rooms are through “gull wing” doors. The materials chosen are long lasting and mostly maintenance free. The pillars are clad in travertine marble. The louvers are in semi-matt stainless steel. The shell is clad in aluminium and, in an honest expression of function, no attempt is made to hide the blue insulation of the shell which is seen through the glass rings. The drop off entrance porte-cochere lights are recessed in the thickness of the concrete slab. Kerbs, bollards and the sloping and curved retaining walls are in white off -shutter precast concrete.

Source: The Green Building Handbook Volume 6

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