Energy performance modeling for buildings is a new field, but one that is getting a lot of interest under the impetus of government mandates and incentives. It's so new that there is no set of standard best practices. Energy modelers are having to make it up as they go. But this is beginning to change. Trailloop has just released an online course for BIM-Integrated Energy Modeling for buildings. The course was created by Jean Carriere who is one of the early pioneers in applied energy performance modeling. Jean has been working commercially in this very new field for about 5 years. Jean also teaches BIM modeling at a local community college.
In the United States according to the Environmental Protection Agency (EPA), buildings are responsible for 65 % of electricity consumption. An important motivation for energy efficient buildings in many jurisdictions are aggressive building codes that push energy efficiency. For example, the 2013 California Green Building Standards Code (Title 24) is one of the first “green” building codes. Other motivations are customer driven certification such as LEED and other "green" certification - LEED v4 incorporates up to 18 credits for demand response - and financial incentives from local governments and power utilities to reduce energy consumption, peak load or both. Government mandates for zero energy buildings (ZEB) have been introduced in E.U., the U.S. and Japan. According to Navigant Research, global ZEB revenue is expected to grow from $629.3 million in 2014 to $1.4 trillion by 2035.
Energy performance modeling is an essential tool for estimating the energy requirements of a new or existing building. An energy performance analysis allows you to determine how much energy your building will consume in a year, assess the most cost effective insulation and glazing, and assess other things that you can do as part of the building design to optimize energy usage. An energy analysis requires a lot of data - geometry of the building, performance characteristics of materials, geolocation and orientation of the building, and so on. Simulation applications allow you to include local environmental conditions and conduct thermal modeling, daylight and airflow simulations. Thermal modeling includes energy consumption, thermal comfort, CO2 emissions, renewable energy integration, and electric power load. Natural lighting includes visual comfort (glare) and the reduction of energy use through natural lighting. Airflow simulation includes external wind simulation, internal airflow simulation, clean room ventilation, and reduction in electrical load as a result of using natural ventilation.
There are many energy analysis tools available (lighting, thermal, emissions, water usage, etc) , many are very complex, and the volume of data that are required is increasing exponentially. Many energy modelers follow a best-of-breed approach so interoperablity is a major challenge in improving productivity in energy performance analysis.
Increasingly for energy modelers the natural place to start is with a Building Information Model (BIM). There are several reasons for this. First of all it is what many of the energy performance analysis packages expect and it is supported by the gbXML standard. Secondly it allows all the information required by the architect, engineers and construction contractors to be accessed in one place. And thirdly it helps in communicating the results of the energy performance analysis to the people who need it including heating and cooling, lighting and other types of engineers, all of whom may require the same information but communicated in different ways.
In most projects the energy modeler is brought in after the building has been designed. If the building was designed using BIM, the starting point is the architect's BIM model and an associated database containing information about elements of the building. Otherwise it is necessary to start with paper drawings and generate the BIM model from scratch. In addition the geolocation and orientation of the building and local environmental conditions are required. The first thing the energy modeler does is to create a parallel BIM model, which is a simplified model derived from the architect's BIM model that contains the key elements that are required for the energy analysis such as simplified walls and floors, room bounding elements, complete volumes, and window frames and curtain walls. The simplified model is exported as a gbXML file and imported into an energy analysis package. The energy performance application is used to run a simulation or several simulations if the energy modeler is asked to consider alternative designs. Finally, a visualization showing energy consumption using the BIM model is used to communicate the results of the analyses.
The Trailloop course covers the energy performance modeling workflow in detail including creating the BIM model, exporting it as a gbXML file, importing the gbXML file into an energy performance package which performs the analysis, and then exporting the results back to the BIM model. In the Trailloop course industry standard tools are used: Revit for BIM modeling (a free version is available for students) and IES VE for building energy modeling (a special low price is available for students).
In his commercial practice, Jean has focused on optimizing the energy modeling workflow so that starting from paper architectural drawings, he can develop the BIM model, compile energy performance parameters, generate a gbXML file, and conduct a complete energy analysis (daylighting, thermal analysis, etc) for the proposed building in as little as two weeks, and then provide weekly performance feedback from design changes.
The BIM-Integrated Energy Modeling Online Course is the most competitive and time-efficient workflow because it avoids rework through integration during the design process, providing an early feedback of LEED credits.
Students learn about the foundations of Integrated Modeling for a seamless integration into the Virtual Environment’s energy modeling application by using a Revit model, and then gain practical experience in solving complex design integration problems. Model elements are precisely placed using a standard set of modeling rules to ensure a predictable quality. Input data is associated with spaces and zone for thermal template data integration through schedules. Techniques are given to troubleshoot and mitigate all errors from the building geometry in order to apply an accurate building envelope.
Once the building geometry is integrated, students learn how to perform early-stage energy simulations to generate preliminary results on energy performance for various systems. They will be able to edit the building geometry and add new forms to the energy model in order measure the impacts of the added building elements. After producing a building loads report, techniques are given to reduce the load to right-size mechanical equipment.
- Construct building geometries in Revit for a seamless integration into IES VE for energy modeling.
- Update the building geometry from design changes and re-integrate it back into the energy model.
- Select appropriate energy modeling input data for building constructions, space types and HVAC systems.
- Describe the differences observed between a baseline run and an energy efficient case for peak heating and cooling load reductions.
- Display the energy/load difference between the baseline run and the energy efficient case using charts, graphics and tabular data.