Unit 3 – Green Building Design

Key Concepts

Green building design is an approach to designing buildings that focuses on sustainability and the long-term environmental impacts of our design decisions.

People use terms such as green and environmentally friendly in many ways. There is no precise definition and a lot of confusion about what being green really means. The term has evolved to encompass a broad range of strategies, all motivated by the common thread of improving the sustainability of our built environment.

The World Commission on the Environment and Development offered this definition in 1987 to succinctly describe the guiding principle that motivates sustainable design:

Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.

This definition still rings just as true today, more than 20 years later.

Motivation

Buildings play a huge role in annual fuel and energy consumption, as well as greenhouse gas emissions. In the United States, buildings consume 39 percent of the annual energy and 68 percent of the annual electricity. Buildings are also responsible for emitting 38 percent of the carbon dioxide, 49 percent of the sulfur dioxide, and 25 percent of the nitrogen oxides found in the air. Furthermore, buildings consume a substantial amount of water, depleting yet another valuable natural resource.

As a long-term goal, green building design aims to create sustainable, self-sufficient structures by using resources wisely and minimizing environmental impacts. By improving the design of buildings with this goal in mind, we can make significant improvements in our overall resource use and environmental friendliness. Throughout the entire lifecycle of a structure, green design aims to reduce resource consumption and minimize emissions and waste.

Green Design Strategies

Many strategies can be employed to improve the sustainability of our building designs. There is no single best approach, but the steps typically include:

Consider the passive architectural design features―including building placement and orientation, massing and form, and the placement of windows and openings―to promote daylighting and natural heating and cooling.
Design the building envelope using materials that minimize energy waste and help to lower the carbon footprint.
Improve the efficiency of the active building systems―including lighting and power, heating and cooling, and water supply and waste―to minimize the demand for external resources.
Use innovative strategies to incorporate renewable and sustainable energy and water resources wherever possible and to reduce reliance on external sources.

Some popular approaches include:

Selecting a sustainable site
Promoting alternate forms of transportation
Using water-efficient landscaping
Reusing wastewater
Harvesting rainwater
Using on-site renewable energy
Using local materials
Using rapidly renewable materials
Using system controls (for example, sensors)
Increasing ventilation
Daylighting

While efficiency and sustainability are the main goals of green design, it is important not to forget the human aspects of a building. When designing a structure, there must be a balance between being environmentally friendly and being usable and comfortable.

Establishing a Green Design Goal

As design teams choose alternative green strategies, it is important to explicitly establish their goals and prioritize them. The goals selected can lead to very different design decisions.

One way to approach this challenge is to first decide what measures will be used to evaluate the effectiveness of an alternative:

Economic impact and estimated monetary savings
Environmental impact and estimated resources savings
Reductions in the size of the carbon footprint
Others

Then the team can establish the target levels of reduction for each of the measures selected to:

Reduce consumption to a target percentage below a baseline level.
Minimize impacts or offsetting them to have a net-zero impact.
Eliminate all dependence on external resources and going off the grid.

Any of these levels would be an example of a sustainable design and a net improvement compared to conventional designs. For this reason, we typically evaluate sustainability in relative, rather than absolute terms.

LEED

The United States Green Building Council (USGBC) created a green building rating system to help promote sustainable building practices. This system is known as LEED®, an acronym that stands for the Leadership in Energy and Environmental Design.

The LEED rating system, which defines standards for measuring how green a building is, encourages building designers, contractors, building owners, and product manufacturers to use sustainable practices by providing recognition for exemplary performance. It has also raised consumer and public awareness of good green design, which in turn encourages all participants to consider sustainability issues as design decisions are made.

Using the LEED rating system, buildings are judged and awarded points for these major categories. The evaluation system was changed in 2009, expanding the credits available in several categories and recalibrating the points required for each level of certification.

Category	Points Available (Pre-2009)	Points Available (Post-2009)
Sustainable Sites	14	26
Water Efficiency	5	10
Energy and Atmosphere	17	35
Materials and Resources	13	14
Indoor Environmental Quality	15	15
Innovation and Design	5	6
Regional Priority	N/A	4
Total	69	110

Figure 3.0.1 lists the specific credits in each category and the points available per the 2009 changes. Based on the number of points or credits achieved, buildings are awarded a level of certification:

Certification	Points Required (Pre-2009)	Points Required (Post-2009)
Certified	26–32	40–49
Silver	33–38	50–59
Gold	39–51	60–79
Platinum	52+	80+

To supplement the materials provided in this curriculum, consider inviting local design professionals to your classroom to present case studies and share their experiences and insights from working with the LEED criteria and evaluation system. For example, consider:

How their project team used the LEED process and the design strategies in the design of a local building.
How the target level of LEED certification was selected for the project.
Which LEED credits were selected as design criteria and how the measured improvements were achieved.

Providing real-world case studies of local building projects will heighten student interest and greatly improve the effectiveness and impact of the curriculum materials presented.

Lesson Roadmap

In this unit, students will learn how to design and evaluate green design measures by exploring:

Passive Design

Building orientation
Building massing and shape
Architectural features—window placement, roof overhangs, and shading features

Building Envelope

Thermal properties of building materials
Thermal transfer
Thermal comfort

Water Use and Collection

Estimating the water demand baseline
Improving efficiency through plumbing fixtures
Offsetting water use through net-zero measures

Power Use and Generation

Estimating the electrical demand baseline
Improving electrical efficiency through fixtures and controls
Offsetting power use through net-zero measures
Payback period

Daylighting

Analyzing daylighting levels provided through architectural features in the building model
Implementing daylighting design strategies

Software Tools and Requirements

To complete the exercises in this unit, students should download the following software programs and install them on their computers and register for the following services:

Download Autodesk® Ecotect® Analysis software from the Autodesk Education Community website.
Access Autodesk® Green Building Studio® web-based energy analysis service from the Autodesk Education Community website and create an account.
Download the Autodesk Green Building Studio Client software from the Green Building Studio web service page to upload building models and designs for analysis.

gbXML: Green Building XML Schema

The gbXML Scema was designed to transfer essential information contained within a building information model. This information includes items such as walls, windows, and room areas, and excludes superfluous items such as furniture, stairs, and appliances.

This format allows for a consistent way to share information between Autodesk® Revit® products and other software tools that adopt the schema. In the following unit, we will be saving our models as gbXML (green building extensible markup language) files in order to transfer data into Ecotect Analysis and Green Building Studio.

Autodesk Green Building Studio

Green Building Studio is a web-based service for use in evaluating the environmental impact of your building design and design alternatives. While the program accounts for location-specific weather data, and reports the amounts of resources used, it is also strongly influenced by economic impact. Tools used by Green Building Studio enable you to assess:

Energy and carbon results
Water usage data
Photovoltaic potential
Daylighting results
Design alternatives

The results in Green Building Studio are often reported in monetary terms that reflect the local costs of utilities.

Autodesk Ecotect Analysis

Ecotect Analysis is a software tool that evaluates the performance of your model based on climate and environmental factors. Ecotect Analysis can import gbXML files of your model and runs them against location-specific weather data. Tools used by Ecotect Analysis enable you to assess:

Whole building energy analyses
Thermal performance
Solar radiation
Daylighting
Shadows and reflections

Ecotect Analysis typically uses data visualization devices such as grids, shaded models, and color schemes to convey the results of the analyses performed. The results are often presented in a form that reflects scientific measures and quantities, rather than monetary measures.

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