Introduction to LEED™
What is LEED?
The LEED system was developed to provide a standard for what constitutes a “sustainable building” and to transform existing building markets so that sustainable design, construction and operation become mainstream practices. The approach taken was to create a “voluntary, consensus-based, market-driven building rating system based on proven technology”.1 LEED aims to improve occupant well-being, environmental performance and economic returns from buildings, using both established and innovative practices, standards and technologies. It is also intended to prevent exaggerated or false claims of sustainability and to provide a common standard of measurement.
LEED was first developed by the US Green Building Council (USGBC) and adopted in the USA. LEED Canada for New Construction and Major Renovations 2009 applies to new designs and major renovations of commercial, institutional or high-rise residential buildings.
LEED offers a third-party certification process whereby points are collected within seven main environmental performance categories (see Table 1). The sixth category deals with Innovation and Design Process and aims to promote whole-building integrated design practices and a new seventh category Regional Priority gives extra points to projects who can show any extra considerations given to any environmental challenges unique to the region of the job site.
LEED represents a consensus-based approach of the members of the USGBC and CaGBC, which include a wide cross section of designers, suppliers, clients, regulators and other interest groups. As of April 2005, over two hundred buildings were LEED certified in North America, and over a thousand projects were registered seeking LEED certification.
Benefits of LEED Certification
Well documented benefits of employing sustainable building technologies include measurable reductions of waste, decreased water use, energy savings, reduced operating and maintenance costs and improved indoor air quality. Less tangible benefits may include improvements in occupant health, employee morale, productivity, recruitment, retention and improved public image for organizations that build green. Research studies 2 point to links between sustainable buildings and improved labour productivity – a business expense that dwarfs other building operating expenses.
Incorporating sustainable features also helps to “future-proof” a building for tomorrow. With rising utility costs, more demanding indoor environmental quality standards, and concerns about the impact of some materials on the environment, new buildings that do not address these issues may find themselves at a competitive disadvantage in the future. LEED accreditation helps to identify leaders in sustainable design and serves as a marketing tool that can be used by building owners to generate increased returns. LEED can also be used to raise consumer awareness of the importance of sustainable design. In addition, many organizations are now requiring LEED certification for their buildings.
How Steel can Contribute to LEED Credits
The following sections review the relevant LEED Canada NC 2009 categories for which steel components can contribute to earning LEED points.
It should be noted that most of the points require a coordinated approach by the design team and cannot be achieved merely by using a particular material or technology. Nevertheless, it may be possible to achieve some points merely by using steel, and use of steel components can contribute to obtaining over 50 points in LEED Canada NC 2009 as part of a holistic approach.
Sustainable Site (SS)
This section of LEED deals with issues related to site selection (brownfield vs greenfield), site design (materials, density, drainage), site access (transport issues and availability of facilities), heat island effects and light pollution effects.
One prerequisite and 26 points are available.
This credit is designed to channel development into urban areas with existing infrastructure, protecting Greenfield sites.
Using steel structures and components can help address many of the problems of building in urban centres. Engineered, prefabricated steel components can be speedily installed reducing construction time and disruption on the site. Furthermore, the flexibility that steel design offers enables difficult urban sites to be more readily exploited. The wide spanning capabilities, fast tract construction, integration of services, just-in-time delivery, reduced storage requirements, less disruption on cramped sites, and lighter weight of steel buildings leading to smaller foundations, all contribute to more workable steel solutions on difficult urban sites. In addition, many steel technologies such as steel pile foundations and roof and wall cladding require little removal of waste from site.
Increasingly, developers in Europe are using steel frame for both residential and commercial building in tight city centre sites due to the speed, prefabrication and reduced disruption.
This credit aims to focus development on previously used industrial or commercial sites with real or perceived environmental contamination.
As with urban sites, contaminated (brownfield) sites developments can benefit from the use of lightweight structures that require less ground work and large-scale prefabrication using steel components which can reduce disturbance of the polluted ground. In some cases this can lead to more cost-effective remediation solutions to deal with the contamination.
This credit includes 1 point for protecting or restoring open space in order to conserve existing natural areas. To achieve this credit the disturbance due to development must be contained within strict limits.
The use of steel structures and components allows much more prefabrication. A key feature of prefabrication is that much of the process is removed from the site to controlled factory conditions. Reducing the amount of time spent on site can lead to less detrimental impacts on the site and locality. The use of steel provides the opportunity for management systems that reduce site disturbance.
Prefabricated hotel buildings can be constructed on site in half the time (or less) of a traditionally built hotel of a similar size, and with less disruption in the locality. This could be reduced further with the use of factory applied claddings. In the catering industry clients have claimed an improvement by a factor of 10 in construction and commissioning timescales for a typical fast food restaurant when using volumetric construction.
This credit includes 1 point for the use of roof surfaces that are EnergyStar compliant, with a high reflectance and emissivity to reduce cooling loads.
Steel roofing and cladding materials are available that meet the EnergyStar labeled requirement with reflectance greater than 0.65 and emissivity greater than 0.9. See:
Energy and Atmosphere (EA)
This category encompasses a number of strategies to help reduce energy use and exploit renewable energy sources to cut greenhouse gas emissions. Other measures aim to protect the ozone layer.
3 prerequisites and 35 points are available.
This prerequisite requires that all LEED certified buildings achieve a base level of energy efficiency. For new buildings in Canada this is set at:
- Model National Energy Code reference building – 23% reduction in energy cost
- ASHRAE Standard 90.1-2007 – 10% reduction in energy cost
In addition, this credit offers further points (up to 19 points) for new buildings if the energy cost is reduced by between:
For major renovations, less demanding standards are set.
Meeting the base standards is generally cost-effective and good business practice. Steel structures can be readily designed to achieve the base levels of energy efficiency required and score additional points depending on the detail design of the building, its location and fuel type used. Examples in Canada include the many light steel frame residential buildings constructed to the demanding R2000 energy efficiency standards. Also, steel frame offices can accommodate high levels of insulation and flexible servicing strategies to maximize efficiency.
The energy calculations required for this credit entail the use of thermal modelling software such as DOE 2.1 to enable designers to investigate, optimize and demonstrate the full annual energy performance. These models allow the effects of thermal mass to be accurately modelled to demonstrate and maximize the potential benefits. Thermal mass is important in buildings for its heat storage capacity, particularly in the cooling season. However, it is not the absolute amount of mass that is most important but how well it is distributed, and how well it is connected with the occupied spaces. Studies have shown that sufficient thermal mass can readily be incorporated in steel frame office buildings to reduce cooling loads, and that the structural framing makes little difference to cooling loads.3 The designer should focus on ensuring that the mass which is present for structural requirements is used effectively for cooling. This means careful specification of finishes to ensure that the mass is not insulated from the internal spaces.
This credit offers up to 7 points for technologies that generate on-site renewable energy for 1-13% of the building’s total energy use.
Steel Cladding is becoming increasingly available with photo-voltaic cells integrated into their surface which can generate on-site electricity. These can be used to gain points under this credit.
Material and Resources (MR)
This section focuses on building and component reuse, waste management and use of recycled, certified and local or regional materials. This section includes complex rules about definitions and measurement methods which affect steel recycling percentages.
One prerequisite and 14 points are available.
This credit offers points for extending the life of existing buildings thus conserving materials that would have been used for a new building. More points are awarded when greater proportions of the existing building are reused.
Steel Frame buildings are flexible and are suitable for reuse. They are also often readily extendable and adaptable to new uses. In refurbishment, modifying and reinforcing of existing structures is an important attribute of steel structures. There are many examples of steel frame structures that have been adapted for a new use, while in some cases steel structures have been dismantled and reassembled in a new location. In addition, the lightweight characteristics of steel structures mean that often additional floors can be added to existing buildings, extending their usefulness.
An example of complete reuse of a steel structural system is the Beaver Stadium at Penn State University. In this case, the entire steel structure was unbolted, dismantled and relocated at a nearby location.
This credit aims to address the huge volume of construction waste generated. One or two points are available for diverting 50% or 75% of the weight of construction, demolition and land clearing debris from landfill disposal.
Steel is a valuable material and is generally either recycled or reused when occurring as part of construction or demolition waste. Thus, any steel generated from demolition can be readily sent for recycling or reuse, thus generating significant benefit for this credit. In addition, the use of steel components on-site generates very little waste, as the components are generally manufactured to tight tolerances in a factory and delivered to site for assembly. Any steel off-cuts that may arise are valuable and can be readily recycled. Thus, using steel structures and other steel components should contribute significantly to reducing site waste.
This credit aims to extend the life cycle of building components by specifying salvaged or refurbished components. This saves the resources needed to produce new components. One or two points are available if 5% or 10% of the total value of building materials comes from reused sources.
Many steel components that are recovered from demolition or refurbishment projects are suitable for reuse. This includes structural sections, cladding, studs and smaller components. Increasingly, designers are sourcing recovered steel components and specifying their use in new projects.
Examples of major projects where recovered steel has been used include the Students Center for the University of Toronto Scarborough Campus (UTSC). The engineers for this project were also working on renovations to the Royal Ontario Museum (ROM) where demolition work provided steel components suitable for use in the new Students Centre. This helped to meet the students’ aims to address issues of environment in their new building. Another example is the Philips Ecoenterprise centre in Minneapolis which use 189 steel joists from a demolished warehouse saving an estimated 50 tonnes of steel.
This credit is calculated using the value of the reused material. Since steel components often have a relatively high value compared to other building materials, they can contribute considerably to achieving this credit. LEED requires that the salvage status of each component be validated, but if the cost of reused components is lower than the new product equivalent it allows the equivalent market value of new products to be used in the calculations.
This credit aims to increase demand for building materials such as steel that incorporate recycled content. The credit differentiates between post-consumer waste and post-industrial waste. One point is available if the sum of the post-consumer recycled content plus one-half of the post-industrial recycled content constitutes at least 10% of the total value of the material for the project (see Table 3). A second point is available if these proportions are doubled.
Steel structures and components can contribute significantly to achieving this LEED credit. One of the greatest environmental advantages of steel is its recycled content. Steel can be recycled an infinite number of times without loss in quality. Thus, a piece of steel can be a can, then a car and then a beam in a building, and be continually recycled. There is no contamination or deterioration of steel construction products made of recycled content, and steel processes provide a reliable recycled product that is truly recyclable. The infrastructure for steel recycling is well established, and its magnetic qualities make it easily extracted from the waste stream.
In nature, waste is food, and in steel production, recovered steel is “food” for new production. Steel is produced through one of two methods: The Basic Oxygen Furnace (BOF) which typically uses about 25% scrap steel, and the Electric Arc Furnace (EAF) which uses greater than 95% scrap steel.
In Canada, both processes are used for sheet steel building products such as roofing, cladding, steel studs, decking and floor joists. LEED certification requires documentation from the steel suppliers verifying the recycled content and manufacturing process. This is available from steel producers or from the AISI website (www.steel.org). The value of a steel frame in a building may in some cases itself be sufficient to account for the required value of materials to achieve this credit.
This credit is intended to increase demand for locally manufactured materials thereby reducing the environmental impacts of transportation and supporting the local economy.
To achieve 1 point, 20% of materials (measured by value) must be extracted, processed and manufactured within 800km of the site, or if rail or water transport is primarily used this distance is extended to 2,400km. For a second point, 30% of materials must meet this requirement. Most scrap used in Canada is from local sources located close to the steelmaking operations.
Indoor Environmental Quality (IEQ)
This section focuses on occupant comfort, indoor air quality, thermal comfort and access to daylight.
One prerequisite and 14 points are available.
This credit requires that any adhesives or sealants used in the interior of the building comply with South Coast Air Quality Management District (SCAQMD) Rule #1168. Sealants and/or adhesives are sometimes used in interior applications of sheet steel building products (i.e. liner panel). There are sealants and adhesives available that are appropriate for these applications that meet the standards in the SCAQMD Rule #1168.
This credit aims to reduce the quantity of indoor air contaminants. One point is available if paints to the Green Seal requirements are used. Steel components are usually painted off-site under controlled conditions. This reduces emissions into the building. Low-emitting paints and coatings can be used on steel to meet this credit requirement.
Two points are available for a credit to maximize daylight and views. One point is achieved if the prescribed daylight levels are achieved for at least 75% of the principal spaces. A second point is available if 90% of all regularly occupied spaces have a view to outside.
The adaptability of steel structures, cladding and partitioning can provide the designer with flexibility and scope to provide good daylighting, and the maintenance of unobstructed views, this meeting the requirements of this credit.
Innovation and Design Process (ID)
6 points are available, there are no prerequisites.
This section allows a building to obtain up to five design innovation points, as well as one additional point for including a LEED accredited professional in the design process.
Credits for Innovation in Design may be awarded for strategies that go significantly beyond what is required in the other LEED credits or for new ideas not covered elsewhere. Steel may contribute some innovative solutions – possible options include design for future demountability and reusability, use of composite members to reduce material volume, use of innovative steel structural solutions that reduce material volume, and integration of structure and services.
For example the Utah Olympic Speed Skating Oval uses an innovative cable suspension system to support a very shallow steel truss roof, which weighs about 600 tonnes (25%) less than competing solutions. The design also reduces the internal volume by about 20% which results in a smaller HVAC system and less energy used for heating and cooling.
Creative use of prefabrication to maximize environmental benefits and improve Health and Safety of the workforce is another option. Moving much of the process into more controlled and comfortable factory conditions enables safety requirements to be more easily met and policed, and healthy and comfortable are more readily maintained.
To support design integration, 1 LEED point is available if the design team includes a LEED Accredited Professional. The steel industry can offer LEED accredited professionals the opportunity to work with project teams.
Regional Priority (RP)
4 points are available, there are no prerequisites.
The intent of this credit is to minimize materials use and construction waste over a building’s life resulting from premature failure of the building and its components and assemblies.
In order to acquire this point, a Building Durability Plan must be developed and implemented according to the standard CSA S478-95 – Guideline on Durability in Buildings. As steel is a durable product with a long life-cycle, it can be incorporated into any building project to achieve the necessary requirements of any Building Durability Plan.
- LEED Reference Guide, Version 2.0, June 2001, USGBC, page 2.
- Fisk, W, Health and productivity gains from better indoor environments and their relationship with building energy efficiency, Annual Review of Energy and Environment 2000, 25, pages 537-566
- Barnard, N. Making the most of thermal mass, Architects Journal, 21 October 1999 Barnard, Nick et al, Modeling the performance of thermal mass, BRE Information Paper IP6/01, Building Research Establishment, UK