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Autodesk Green Building Studio Adopts the newest DOE-2.2 version (48r in 64-bit) for our February 14, 2014 Release

marjoriestein
February 18, 2014

Who is this for: Users of Autodesk Building Performance Analysis tools who want to know how changes to the DOE-2.2 simulation engine is impacting the energy results in the new release of Green Building Studio.

Takeaway: The February 14,  2014 release of Green Building Studio (GBS) web service now uses the newest version of DOE-2.2-48r, which includes Autodesk code enhancements. Revisions to the DOE-2.2 software result in some changes to the GBS energy analysis results (thereby affecting Revit and Vasari energy analysis results).

Autodesk and Intel teamed with JJHirsch and Associates to embark on making DOE-2.2 and eQuest more BIM friendly. This included speed enhancements, better shading polygon support, and increased limits for several objects. The current release of eQuest and DOE-2.2 includes these enhancements and are available at DOE2.com.

Autodesk Green Building Studio (GBS) uses the DOE-2.2 simulation engine for calculating the hourly, whole building energy usage of your project. The DOE-2.2 software was developed by James J. Hirsch & Associates (JJH) in collaboration with Lawrence Berkeley National Laboratory (LBNL). DOE-2.2 has been validated by Lawrence Berkeley National Laboratory and the Los Alamos National Laboratory.

GBS has adopted the newest version of DOE-2.2 (version 48r in 64-bit), for our February 2014 release. The baseline used for the following comparisons is the Green Building Studio October 2013 build, which uses version 44e4 of DOE-2.2. The 64-bit version allows us to utilize more of our cloud-based server’s hardware and memory, which results in an increase in the simulation speed.

Simulation time of a GBS test model (GSA Headquarters, used in the Autodesk Benchtop Commercial Office Project), were reduced from 50 seconds with DOE-2.2 44e4 (used by the previous GBS release) to 32 seconds with DOE-2.2-48r 64-bit (used by the February 14, 2014 GBS release). We expect typical reductions in simulation time with this new release of approximately 30 percent.

The validation results presented here are from 464 test cases covering 4 conceptual models, 16 climate locations, and 29 different building types. The change in annual electricity consumption ranges between -2.1% to 3.0%, with a median change of 0.4% and an average change of 0.4%. The fuel usage differences range from -7.6% to 6.9%, with a median of -1.0% and an average of -1.2%. One of the instances of the largest change in annual fuel usage is the Fargo ND Single Family test model, which is described below.

all-files-electric

Changes in Annual Electricity Uses in 464 Test Cases

 

all-files-fuel

Changes in Annual Fuel Uses in 464 Test Cases

 

Some of the main computational changes to DOE-2.2, which impact the GBS energy results, include modifications of window convective calculations per NREL documentation, and the addition of an ASHRAE enhanced infiltration correction.

Other significant changes to DOE-2.2 version 48r include conversion to Intel Fortran and C compilers; replacement of triangular or rectangular shapes for shading surfaces with rich polygons (up to a maximum of 128 vertices); and the increase in the number of limits of many model parameters. This will enable the energy analysis of more complex Revit models that may have previously been exceeding the the previous version’s limits.

Refer to the DOE-2.2 New Features documentation, and the Description of Cumulative DOE-2.2 Bug Fixes documentation for more details.

 

Baseline (DOE-2.2-44e4) limits New DOE-2.2 version 48r limits
Number of spaces 4096 9999
Number of exterior walls 8192 64,000
Number of windows 8192 64,000
Number of interior walls 8192 64,000
Number of Underground walls 8192 10,000
Number of doors 1024 4096
Number of building shades 1024 10,000
Number of polygons 32,768 120,000

 

Below is a summary of the energy results changes from two of our test models.

One of the office test models is located in Boston MA, with an area of 25,000 square feet, five floors with approximately 40% window-to-wall ratio. The largest end-use change for this test model is a reduction in heating energy (11.5%). The largest heating load component of this test model is window conductivity (approximately 60%). One of the changes to version 48r of DOE-2.2 is the modifications of window convective calculations, therefore it is expected that this model would have changes in heating energy. The window conductivity heating load is reduced an average of 10% from the baseline to the new release.

office-cropped

Boston MA Office Test Model

Office Test Model Annual Electricity Use (kWh) HVAC Lighting Misc Equipment Total
Baseline 115,183 82,451 124,837 322,471
February 2014 Release 117,446 82,451 124,837 324,734
Change 1.9% 0.0% 0.0% 0.7%

 

Office Test Model Annual Fuel Use (Therms) HVAC DHW Total
Baseline 2,801 476 3,277
February 2014 Release 2,513 476 2,989
Change -11.5% 0.0% -9.6%

 

office-heating-loads

 

office-window-conductivity

 

The Fargo ND Single Family test model is 3000 square feet, including a conditioned underground level. The largest change is a 7% increase in heating energy, with the largest heating load component being infiltration. One of the changes to version 48r of DOE-2.2 is the infiltration correction, therefore it is expected that this model would have changes in heating energy.

 

single-family-cropped

 Fargo ND Single Family Test Model

 

Single Family Test Model Annual Electricity Use (kWh) HVAC Lighting Misc Equipment Total
Baseline 3,416 4,512 5,246 13,174
February 2014 Release 3,486 4,512 5,246 13,244
Change 2.0% 0.0% 0.0% 0.5%

 

Single Family Test Model Annual Fuel Use (Therms) HVAC DHW Total
Baseline 1077 149 1226
February 2014 Release 1161 149 1310
Change 7.2% 0.0% 6.4%

 

single-family-heat-loads

 

We’d like to hear from you: Is this information helpful, and what other information pertinent to GBS energy analysis calculations would you like to see? Contact us at bpa.team@autodesk.com, or through the Autodesk Green Building Studio Community Forum.

marjoriestein

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