E-Quest (Group Project) _ Tutor. Khee Poh Lam
One Montgomery Plaza _ Equest, Revit Modeling
This study represents energy simulation analysis of an eleven-story office building located in Norristown, Pennsylvania. Keeping the simulation engine DOE-2 constant, Green Building Studio and eQUEST are utilized to run energy simulations to obtain results for this building. Three main variations are considered for this parametric study: opaque, glazing building materials, and internal load of building operation. The weather condition is limited within Pittsburgh area to zone 5A. Not only comparing energy consumption results but also investigating the confounding factor of each variations are examined to bolster the depth of reasoning and to guarantee more accurate energy modeling results.
Because Green Building Studio (GBS) and eQUEST used the same simulation engine DOE-2, the difference between the baserun results were negligible (relative difference of total energy was approximately 0.0002%). The few inputs that changed and rounding errors might have been the contributing factors to the minute difference in results.
The building is a general commercial building constructed in 1973. The size of the building is 20,000 square meters. The basic exterior wall was constructed using masonry brick. The construction of the wall assembly is limited to steel stud and Concrete Masonry Unit (CMU).
Different from GBS, users can assign materials layer by layer for the wall assemblies using eQEUEST. The wall parametric study is categorized into steel stud and CMU assembly with several different types of wall insulations. The primary goal of this study is to define the best performing wall assembly while maintaining the existing building materials that were used in the 70’s. In each steel stud and CMU systems, wall insulation materials are controlled to detect condensation issues in the wall assembly
Issue of Condensation
To bolster the parametric study, additional studies were conducted taking into account the condensation issues. If relative humidity is over 100 percent, condensation could occur in that layer. Since eQUEST is capable of assigning materials layer by layer, the corresponding layers in WUFI can be easily applied to investigate condensation problems. This approach would be a great supplemental study because eQUEST alone is not capable of identifying condensation problems. Based on the result of WUFI analysis, condensation was discovered in the CMU 3 and steel stud 3 between the exterior brick and the air gap layer.
Core zoning division by different usages and its ratio diagram core thermal zone covers the central plan. With this perimeter, two distinctively different zones are contained in one thermal zoning. Thus it can be divided into two conceptual usage zones. Later, it affects scheduling and occupant rate. For example, the central occupants’ rate is the average value of two different zones: regular scheduling zone and equipment zone (stair, elevator, and electrical room).
From the comparison data above, the time schedule of occupancy rate and the lightining usage rate is quite similar in the ASHRAE and CBECS, but that of eQUEST default is distinctively different. Moreover, the energy consumption total value of the eQUEST default is also different. Therefore, the default value in the exact scheduling for the eQUEST simulation is meaningless due to its inaccuracy.
The general scheduling graph follows the shape of the latter two graphs. CBECS compared to ASHRAE has more realistic benchmark based on the conducted survey. Therefore, the basic occupancy scheduling might be based on the schedule of CBECS’s survey.
eQUEST, the most widely used BEMS tool in the building industry, enables us to perform parametric analysis in further detail unlike the GBS. eQUEST provides greater flexibility to alter variety of performance variables. For example, GBS only allows users to make a selection among limited number of building components but eQUEST library allows utilization of building component’s data to a much larger number. In the wall/roof/floor/window construction, layer by layer configuration is available along with the user’s selection. Making realistic assumptions enables eQUEST to perform as more effective simulation tool throughout the entire building process.
However, there are number of drawbacks in the eQUEST software. First, even though the tool allows us to enter input data in detail, the data entering process is not user-friendly. In order to obtain the most accurate result possible for the whole-building simulation, thousands of more input data is required. With the exception for wizard tool, eQUEST does not have the feature of streamlining the data-entering process. Tedious task of entering all the data might cause low user productivity and delayed simulation process.
Second, unlike web-based tools like the GBS, eQUEST does not offer multiple user environment confining users to work only linearly process by process which might be time consuming for integrated team projects.
Third, well-informed guide or tutorial for novice users is not available. While the GBS is a simplified tool, eQUEST users should be aware of what they are capable of by using the tool. However, the tutorial distributed by the U.S. Department of Energy does not contain instructions for detailed building simulation with externally designed model and only contains guides for the wizard tool. Novice users need to exert extra effort into getting familiar with the tool in addition to the modeling and analyzing procedures.
Nonetheless, there is no doubt that eQUEST has the potential in having a powerful DOE-2 engine with relatively user-friendly interface when compared to other detailed simulation tools. Through this study, we have learned that the most important factor in building simulation is understanding the metrics behind the simulation tool and the actual building environment, not the tool itself.