Transcript Green Building Studio The Pursuit of NOW!

Autodesk Sustainable Design Curriculum
Lesson Seven: Modeling Sustainable Building Construction
Sustainable Construction Management
 Modeling Green Construction
 Net Present Valuation
 Life Cycle Assessment
 Embodied Energy versus Operating Energy
 Prefabrication
 BIM Tools and Sustainable Construction
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© 2009 Autodesk
Sustainable Construction Management
For the sake of completeness, and to keep this curriculum firmly grounded in reality, a list of the
construction trades, as compiled by the U.S. Department of Labor, is included below. Without the
involvement of these construction professionals, no sustainable design project would ever be built.
The building construction trades include:
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Boilermakers
Brickmasons, blockmasons, and stonemasons
Carpenters
Carpet, floor, and tile installers and finishers
Cement masons, concrete finishers, segmental pavers, and terrazzo workers
Construction and building inspectors
Construction equipment operators
Construction laborers
Drywall installers, ceiling tile installers, and tapers
Electricians
Elevator installers and repairers
Glaziers
Hazardous materials removal workers
Insulation workers
Painters and paperhangers
Pipelayers, plumbers, pipefitters, and steamfitters
Plasterers and stucco masons
Roofers
Sheet metal workers
Structural and reinforcing iron and metal workers
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Sustainable Construction Management
There are four main areas that the USGBC LEED standard recognizes that construction operations
can align with to contribute to the sustainability of a building project:
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Construction waste management
Erosion and sedimentation control
Limiting the footprint of construction operations
Construction indoor air quality
Additional opportunities for greening of a construction operation include:
• Recycling of site materials such as topsoil, lime rock, asphalt, and concrete into the new
building project.
• Paying attention to moisture control in all aspects of construction to prevent future mold
problems.
• Minimizing the impact of construction operations, such as compaction and unnecessary
destruction of trees on the site.
The ability to model these aspects of construction enables construction managers to plan in
advance to perform what-if scenarios, and to easily adjust their operations as environmental,
social, and economic conditions change.
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Sustainable Construction Management
Construction costs related to the initial establishment of the facility include:
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Land acquisition, including assembly, holding, and improvement
Planning and feasibility studies
Architectural and engineering design
Construction, including materials, equipment, and labor
Field supervision of construction
Construction financing
Insurance and taxes during construction
Owner's general office overhead
Equipment and furnishings not included in construction
Inspection and testing
Operation and maintenance costs that arise in subsequent years over the project life cycle include
the following expenses:
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Land rent, if applicable
Operating staff
Labor and material for maintenance and repairs
Periodic renovations
Insurance and taxes
Financing costs
Utilities
Source, Chris Hendrickson, 2009, "Project Management for Construction", Dept. of Civil
Owner's other expenses
and Environmental Engineering , Green Design Institute at Carnegie Mellon University.
© 2009 Autodesk
http://pmbook.ce.cmu.edu/).
Modeling Sustainable Construction Management
Illustration of a concrete-placing simulation model. Source, Chris Hendrickson, 2009, "Project Management for
Construction", Chapter 4, "Labor, Material and Equipment Utilization.“ Dept. of Civil and Environmental Engineering ,
Green Design Institute at Carnegie Mellon University. http://pmbook.ce.cmu.edu/).
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Modeling Sustainable Construction Management
Top: Formula for unit cost method of estimation, based on labor, material, and equipment. From Chapter 5, “Cost Estimation.“
Bottom: Illustration of planned versus actual expenditures on a project. From Chapter 12, "Cost Control, Monitoring and Accounting."
Source, Chris Hendrickson, 2009, "Project Management for Construction", Dept. of Civil and Environmental Engineering , Green Design
Institute at Carnegie Mellon University. http://pmbook.ce.cmu.edu/).
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Net Present Valuation
Building information modeling (BIM) tools lend themselves well to the financial appraisal of longterm projects and cost estimation during design and construction.
The primary tools for calculating and communicating this type of financial information are
spreadsheets and graphs that use financial equations.
BIM makes it possible to accurately estimate the “first” capital costs of construction, as well as the
total operating expenses, also referred to as life cycle costs, associated with a variety of sustainable
design and construction scenarios.
The standard method for long-term financial appraisal used for capital budgeting is called Net
Present Valuation (NPV).
“NPV compares the value of a dollar today to the value of that same dollar in the future, taking
inflation and returns into account. If the NPV of a prospective project is positive, it should be
accepted. However, if NPV is negative, the project should probably be rejected because cash flows
will also be negative. “ (“Net Present Value “ Investopedia, http://www.investopedia.com/terms/n/npv.asp)
Using financial modeling techniques such as NPV, developers, designers, engineers, and builders can
use BIM to more accurately describe how the practice of sustainable design can potentially reduce
the costs of constructing and operating a building, and generate a solid return of the investment of
precious financial capital.
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Net Present Valuation
Where:
t = Time of the cash flow
n = Total project time
r = Discount rate
Ct = Net cash flow at time t
C0 = Capital outlay when t=0
NPV Example
An investment with an initial cash outflow
of $100,000 pays back $34,432 in the first
year, $39,530 in the second year, $39,359 in
the third year, and $32,219 in the fourth
year. If the rate of return is 12%, find the
Net Present Value (NPV).
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Life Cycle Assessment (LCA)
According to the American National Standards Institute (ANSI) and the International
Organization for Standardization (ISO), LCA is a “compilation and evaluation of the inputs,
outputs, and the potential environmental impacts of a product system throughout its life cycle”
(ANSI / ISO 1997). ISO’s LCA standards state that a LCA incorporates a goal and scope definition,
life cycle inventory (LCI), and life cycle impact assessment (LCIA).
“A well performed LCA is a
systematically inclusive inventory and
impact assessment for each life cycle
stage of a given product.
The phases for which impacts are
determined often include resource
extraction, material production,
manufacturing, assembly, use, and
disposal (reuse, recycling,
incineration, or landfill).”
Aurora Luscher Sharrard, 2007
"Greening Construction Processes Using an InputOutput-Based Hybrid Life Cycle Assessment
Model" Dept. of Civil and Environmental
Engineering , Green Design Institute at Carnegie
Mellon University
© 2009 Autodesk
Life Cycle Assessment (LCA)
According to the American National Standards Institute (ANSI) and the International
Organization for Standardization (ISO) LCA is a “compilation and evaluation of the inputs,
outputs, and the potential environmental impacts of a product system throughout its life cycle”
(ANSI / ISO 1997). ISO’s LCA standards state that a LCA incorporates a goal and scope definition,
life cycle inventory (LCI), and life cycle impact assessment (LCIA).
Aurora Luscher Sharrard, 2007
"Greening Construction Processes Using an Input-Output-Based Hybrid Life Cycle Assessment Model" Dept. of Civil and
Environmental Engineering , Green Design Institute at Carnegie Mellon University
© 2009 Autodesk
Embodied Energy versus Operating Energy
Embodied energy is defined as the sum total of available energy that was used in the
work of making a product, and that is necessary for its entire product life cycle.
Some embodied energy units that have gained some acceptance are MJ/kg (megajoules
of energy needed to make a kilogram of product) and CO2 (tons of carbon dioxide
created by the energy needed to make a kilogram of product).
The “operating energy” of a building design is a fairly straightforward concept; it can be
measured by means of reviewing the fuel and utility bills, and all of the individual energyconsuming components of an existing building of a similar construction type and end
use.
This serves as a “baseline” for modeling alternative designs.
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Embodied Energy versus Operating Energy
The most well known and widely adopted method for estimating a baseline operating energy
cost of a building that has not yet been built is the 90.1 standard developed by the American
Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the Illuminating
Engineering Society of North America (IESNA).
This standard has been in use for over 30 years and continues to be updated.
Some research indicates that the operating energy usage of a building is at least an order of
magnitude greater than the initial embodied energy of the materials used.
This depends to a large degree on the lifespan of the building. In the U.K., the average lifespan
of a building is 132 years. In the U.S., the median office building lifespan is 73 years. The average
lifespan of a building in Tokyo is 25 years. In China it is less than 10 years.
The shorter the lifespan of the building, the more relevant an embodied energy analysis
becomes. The longer the building lifespan, the more relevant the operating energy usage
becomes.
See http://www.canadianarchitect.com/asf/perspectives_sustainibility/measures_of_sustainablity/measures_of_sustainablity_operating.htm)
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Prefabrication
Although it has recently gained attention as a “greener” way of building, the prefabrication of
building components and of whole buildings is not a new concept.
Prefabricated homes and other building types were produced during the 1840s and 1850s Gold
Rush in the United States, when kits were produced in order to enable Californian prospectors
to quickly and effectively construct living accommodations and public buildings.
Today, building component manufacturers, using techniques developed by the automobile and
airframe industry and other manufacturing industry segments, can offer sophisticated
aluminum-framed, face-sealed, water-managed, and pressure-equalized rainscreen curtain
walls, containing in-fills of glass, metal panels, or thin stone, all at a very high quality and a
relatively low price.
Entire steel-frame buildings covering thousands of square feet are now being efficiently
prefabricated. Manufacturers have been steadily improving their ability to control quality and
reduce waste by pre-engineering and automating many aspects of construction in a controlled
factory environment. The most notable examples come from the transportation sector, where
entire bridges are being successfully prefabricated and quickly installed.
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Prefabrication
Left: A 771-metric ton (850-ton) prefabricated steel truss span being set in place over rail lines in New Haven, CT, in one operation at midnight to
avoid impacts on a vital railroad corridor. Source: Connecticut Department of Transportation, Public Roads Magazine, United States Department of
Transportation, Federal Highway Administration.
Right: Diagram of a portion of the Baldorioty de Castro Avenue overpasses in San Juan, PR, showing some of the elements of a concrete bridge that
were built offsite, transported to the construction site, and then put in place. Source: Precast/Prestressed Concrete Institute, Public Roads
Magazine, United States Department of Transportation, Federal Highway Administration.
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BIM Tools and Sustainable Construction
Although BIM tools and processes are relatively new to the construction industry, some forwardlooking firms have already adopted the technology and are making strides in applying it to the
process of sustainable design. Using BIM technology, designers and builders can produce and
share a range of vital information, including:
Display: Planning information, site history, soil conditions, survey, utility availability, weather
conditions (prevailing winds, velocity, rainfall, snow load, degree days, sun angles), seismic
conditions, zoning, key public officials (city/town council, congressional district), planning
commission members, zoning board members, inspectors, public meeting dates, and points of
contact.
Collaboration: Ability to share information between members of the design team and public
officials. Software interoperability with various design packages. Development of master
production schedules, work in place, requests for information, change orders, estimates and
actual costs, materials testing results.
Data Capture: Tools to extract information necessary for the facility owner and operator. Includes
extracting information from invoices related to model and serial number, and date purchased and
installed. Collection of cautions and maintenance schedules, identification of hazardous materials,
and any off-gassing issues.
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Summary
Without active engagement of the construction team, early in the design process,
sustainable design goals will never be achieved.
Construction managers and the design team need to collaborate at the outset of the
project, to share their knowledge and insights.
Information modeling techniques and tools can be used to powerfully bridge
disciplinary and professional boundaries, and to perform simulations and contingency
analyses that enable the entire project team to collaborate at very high levels of
performance and accountability, regarding financial, social, and environmental risks
and rewards, costs and benefits.
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