First it needs to be recognized when designing high performance buildings that we are too limited if we rely on a single energy model which simply calculates overall loads. The concept of multiple models appears inefficient and a departure from what we want out of BIM, but is a reality that can be efficient with a clear stream of data with a clean file exchange.
If we look at the current process we see that engineers are building multiple energy models to fulfill two requirements:
- Peak loads to size equipment
- Overall energy consumption for compliance with local code
What hasn't yet worked well are the efforts made to integrate energy models into the design process. Most efforts in the US to improve this process focus on reassigning the task of energy modeling to the architects who are more able to do it early while (whilst) the results can influence the design. Later in the process the engineer will take charge of the energy model, in theory. Engineers are very excited about the potential to spend less time modeling geometry, but still argue that they need to be brought into the process earlier as they don't particularly trust the architect to do this alone, and will often remodel everything again the traditional way just to validate their results.
The US approach has greatest potential for small offices where the architect often performs tasks without the help of consultants and can now achieve more information than they could previously. Medium and large design firms prefer to rely on consultants for most everything which requires advanced knowledge and skills. To build and understanding an energy model requires advanced abilities--to convey the results effectively, but also to trust them in the first place.
Diagram representing Geometry calculations for environmental analysis
Due to tougher energy regulations Europe and the UK have had more experience and have seen a slightly different process evolve. UK engineers have a greater involvement earlier in the project where they actually use their knowledge and experiences to bully architects into making better design decisions. Architecture firms often bring trusted engineers into sustainability charrettes, or "surgeries," where they will critically evaluate designs for multiple projects that they are not working on. When their involvement begins on a project there is immediately a back and forth between their energy model and architectural analysis models that are focused on specific tasks.
By assigning tasks to the architect the engineer can set the parameters for high performance design that allow the architect to creatively explore and evaluate multiple options. These tasks could be minimizing solar radiation during peak hours, redesigning inefficient shading devices, redesigning the forms or the facade to allow more daylight into spaces, and other ways to reduce loads that the architect can measure without a full energy model. To visual this more clearly I've created a project timeline.
This timeline is front loaded in that Pre-Design makes up about one third of the analysis effort, Concept and Schematic phases combined are the next third, and there is even an analysis phase during Due Diligence. The first two project phases belong to what some buildingSMART experts describe as the Building Investigation Modeling phase, while the Due Diligence here is a new concept for most that will prove to be invaluable to the process. We are all familiar with architectural due diligence relating to local codes and site history and the term "environmental due diligence" referring to site investigation for pollution hazards. But to commit to high performance design we need a broader background check and an understanding that sunlight, wind, water, and daylight are not just opportunities but are also hazards if not fully understood. Before a single line is drawn, collaborative due diligence should help us understand when we will have heating loads, cooling loads, peak values, daylight opportunities/constraints, wind opportunities/constraints, on-site renewable opportunities and more. This information can be gathered from many different sources, but when related to energy performance the MEP engineers should be utilized to set design guidelines from their knowledge of building type and location, or from a basic energy model. Before the designer draws a single line they should have a clear direction of what not to do and where their opportunities lie.
There are many reputable software packages that are able to calculate total energy loads, fewer that are trusted or able to design equipment around peak loads. The software that ultimately will excel in energy modeling will be one that is accepted by local building codes across the globe. But perhaps more importantly this software will be able to reuse architectural design models, architectural construction models, and will promote interoperability by cleanly exchanging data between all design and analysis platforms.
When it comes to environmental analysis for evaluating specific issues early in design there is currently no software comparable to Ecotect in either function or interoperability. But Ecotect is particularly easy to support philosophically because of its commitment to interoperability, which is imperative for our industry to move forward.
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