AECbytes Tips and Tricks Issue
#52 (July 20, 2010)
Using ArchiCAD for LEED Calculations
Thomas M. Simmons
President, ARCHVISTA Building Technologies
In order to gain the LEED credits required for LEED certification of a project, calculations must be utilized to determine whether the project meets a credit threshold. These calculations will also need to be recalculated during the design of a project to accommodate modifications and revisions to the design.
ArchiCAD cannot automatically validate your LEED certification; however, ArchiCAD’s BIM database is an excellent system for the calculation of requirements for LEED credits that is typical during the life of a project. In addition, ArchiCAD’s BIM engine can be used to verify project data and provide calculations for the certification process.
In this article, we will review how to create a “Sustainable Site” calculation for the LEED category, “SS Credit 7.2 - Landscape & Exterior Design to Reduce Heat Islands, Roof Surfaces.” To qualify for this credit, a project must provide area calculations demonstrating that the green roof system covers at least 50% of the total roof area. In this example, we will set up an Interactive Schedule displaying the required data to produce a Roof Surface Calculation that can be used to meet the calculation requirements.
Step 1: Add Green Roof Materials to the Material Settings
In order to assign a green roof material to the roof, we must first add a green roof material to the Material Settings so that we can select this material in the Roof Tool. To begin this step, open the Material Settings from the menu Options > Element Attributes > Materials.
Within the Materials Settings dialog, select the “07 | Asphalt Shingle” material within the default settings, and click the Duplicate button. To create the new material, enter the new name for the material as “SS | GreenGrid Vegetated Roof.”
By giving the name a prefix of “SS,” we can organize all the Sustainable Site materials together within the materials list. You may also want to set the Surface Color to green in the Exposure to Light tab and select an image for the material in the Texture tab.
Step 2: Set up a Custom Schedule using the Scheme Settings
The next step is to create a custom Interactive Schedule to track this material. To do this, we need to create a schedule to calculate the total green roof material as well as a second schedule to calculate the total roof surface. We can then use these two schedules to determine if we meet the LEED requirement that the green roof system covers at least 50% of the total roof area.
Let’s start by opening the Scheme Settings dialog from the menu Document > Schedules & Lists > Schedules > Scheme Settings. Within the Scheme Settings, click the Create New button to add a new scheme. Within the Add Schedule Scheme dialog, select the items to list as “Construction Elements.” Next, set the ID as “SS 7.2” and the name as “Reduce Heat Islands, Green Roof.” Click the OK button when finished. A new Interactive Schedule is now available within the Scheme Settings.
Step 3: Configure the Criteria within the Scheme Settings
Now let’s define what elements within our project we want to display within our schedule. To do this, set the Criteria as “Element Type” and “Is,” and the Value to “Roof.”
Click the Add button to add a new criteria so that we can define the Element Type in further detail. Select the “Top Material” option as a Criteria to represent the Roof material surface for the building. Then set the Value of the material to “SS | GreenGrid Vegetated Roof” that you created earlier.
If you want to track additional roof materials, repeat the above step for the Value and after each material added, set the and/or option to “or.”
Step 4: Configure the Fields within the Scheme Settings
Next, we need to establish what type of data to display based on the criteria we specified above. In this step, we will set the Fields that will be displayed within the Interactive Schedule. With the Scheme Settings dialog still open, click the Fields tab to view the Available Parameters we can use as fields.
We will add three parameters to the Schedule Fields as follows: Quantity, Top Material and Top Surface. To do this, click the General parameters option in the Available Parameters, click the Quantity parameter, and click the Add button at the bottom of the dialog to add it to the Schedule Fields.
Next, click the Roof parameters option in the Available Parameters, click the Top Material parameter and click the Add button at the bottom of the dialog to add it to the Schedule Fields. Repeat this step for the Top Surface material directly below the Top Material.
Finally, click the Top Surface field in the Schedule Fields column and click the Sum button to total the calculated roof surfaces. The schedule to calculate the roof surfaces for green roof materials is now complete. Click the OK button to finish the schedule.
Step 5: View the Interactive Schedule
You can now assign the green roof material to roofs within your project and then view the Green Roofs schedule from the following menu: Document > Schedules & Lists > Schedules > SS 7.2 Reduce Heat Islands, Green Roofs.
The Interactive Schedule will open and display the three fields you created, along with the details for each green roof element within your project, based on the material you specified in the criteria.
Step 6: Compare to Total Roof Surface Area
To determine whether your project meets the LEED requirement of “green roof system covers at least 50% of the total roof area,” you will need to create a second schedule that calculates the total roof surface area. To do this, follow the same steps above to create the Green Roofs schedule with the following changes.
Open the Scheme Settings, select the “SS 7.2 Reduce Heat Islands, Green Roofs” you created above, and click the Duplicate button. Change the Name to “Reduce Heat Islands, Total Roofs” and click the OK button when finished.
In the Criteria tab, select the Top Material criteria and click the Remove button. Now click the OK button to complete the second schedule.
To view the total roof schedule, select the name from the following menu: Document > Schedules & Lists > Schedules > SS 7.2 Reduce Heat Islands, Total Roofs.
Now you can compare the calculated results of the two schedules to determine if the green roof surface area calculated in the first schedule is 50% or more of the total roof surface area calculated in the second schedule. Thus, in the example presented here, 6,030 sq. ft. divided by 11,665 sq. ft. shows that the green roof is 51.6% of the total roof area.
This article has attempted to show that if we use the data from a BIM model, we can decrease the time that is necessary to create the required LEED calculations and realize greater accuracy. However, using ArchiCAD for “Sustainable Site” calculation is only one way to exploit the power of BIM for LEED certification. In actuality, there are several ways ArchiCAD can be used within the LEED calculation and management process.
The following are methods I taught recently during a four-part LearnVirtual online training series focused specifically on LEED credit management, calculations, and energy evaluation:
- Organizing the LEED Documentation
- Managing an Interactive LEED Credits Checklist Schedule
- Creating Calculations for LEED Credits:
- Materials & Resources Calculations
- Water Efficiency Calculations
- Building Reuse Calculations
- Daylight & View Study Calculations
Here is an example of the interactive “LEED Checklist Report” that is used to track the LEED categories, possible points, criteria status and earned points. The steps to create this report are outlined in the series mentioned above.
If you’re interested in furthering your knowledge on these topics, as part of your LearnVirtual membership, you will have access to recordings of each eClass in the series mentioned above, as well as over 160 other recorded eClasses on a wide range of topics including modeling techniques, drafting techniques, process management, revision management and design review. Also, new LIVE eClasses occur each week! To learn more about LearnVirtual, go to www.learnvirtual.com.
About the Author
Thomas M. Simmons, the founder of ARCHVISTA, Inc. and LearnVirtual, has spoken at major industry events including AEC Systems, Ecobuild, AIACC Desert Practice Conference, and the AIACC Monterey Design Conference. He has authored several books on Building Information Modeling, ArchiCAD and architectural technology. He was formerly the Director of Technology with the award winning firm of EHDD Architects, San Francisco, and has earned a Masters of Architecture from UC Berkeley. He can be reached at email@example.com.
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