Engineers have conducted performance analysis of buildings for decades. MEP engineers responsible for ensuring that mechanical systems met the heating and cooling requirements of a building, would model systems to ensure they met the rigors of operational use. Gradually, as sustainability gained importance, the definition of performance expanded to include sustainability performance of the building, and sustainability impact of design decisions. Naturally, engineers used their skills to help evaluate energy efficiency of buildings & increasingly started working as part of design teams with architects. They also brought their tools with them (e.g. eQUEST, TRACE, etc). However, there were salient differences in the nature of modeling with the expanded definition of performance.
Performance based design is not performance analysis
Modeling of HVAC systems in order to evaluate its performance was primarily done to reduce the risk of the system not meeting desired performance goals. Such analysis often led to changes in various aspects of the HVAC system that was chosen, e.g., duct sizing, system capacity, fan size etc. While these can be construed as design decisions, they are of much narrower scope & scale than design decisions that impact sustainability of the building. Building performance is impacted by decisions ranging from its siting, form & orientation, its envelope as much as it is impacted by mechanical systems. A vast majority of these decisions are made by stakeholders other than traditional MEP engineers. For instance, an architect is responsible for the vision of the building & responsible for much of what’s visible. Many decisions made by architects impact the building’s performance. An architect might choose to glaze the west facade for beautiful views not realizing that the peak gains in the adjoining space will significantly increase the peak cooling load, and forcing the design team to choose an HVAC system that is energy inefficient in order to meet the demand. This seemingly well intended decision will result in a highly inefficient building. A building might have many fathers but it’s primarily attributed to the architect responsible for designing it. This brings me to the 2nd point.
Performance based design is everyone’s job
In the building design process, decisions are made throughout from early sketches to construction. All these decisions have an impact on the building’s performance but none quite as much as an architect’s decisions during the early stages of design. These decisions last the longest in terms of a building’s lifecycle (50 years in America, close to a century in Europe). This is in contrast to mechanical systems that can be upgraded every decade or two, and control systems which are possibly upgraded even more frequently. The decisions about a building that an architect makes are also nearly impossible to change, without reshaping the building itself. Most architects understand the high influence of their decisions to the buildings’ life-long performance. However, the nature of tools needed to be effective at performance based design is uniquely different from tools that were historically used for performance analysis.
Performance based design requires a new generation of software
One of the primary reasons engineers offered advice on performance based design was due to a natural transfer of their skills (in terms of understanding performance) & software tools to the new world of sustainability. However, this runs head long into the reality of design as design requires multiple stakeholders with diverse skill sets. Decision making at the earliest stages of design tends to be far more rapid, and wide ranging than decisions at the later stage which are narrower in nature, as illustrated elegantly by the MacLeamy curve:
Further, performance of the building is an outcome of design decisions, and often a criterion that impacts these design decisions, much like other criteria e.g. floor area requirements. This implies that performance analysis isn’t a “thing” that happens when design is done. Quite contrary, it drives design as an integral part of the design process.
Unfortunately, traditional tools were seated in a world where performance analysis was done almost independent of the architectural design. Migration of these tools to the world of architecture creates fairly predictable tensions. Architects don’t think they have time for performance analysis, and they often believe it’s the engineer’s job. If architects are presented with software that allows them to design without artificial limitations, and helps them understand & communicate the performance impact of their decisions as part of designing, architects will naturally embrace performance based design, and we will witness a sea change in the nature of built environment.
Performance based design requires a new set of skills
Architects may no longer be master builders in the traditional sense, but the sheer breadth of information they process and decisions they make remains daunting. Performance based design requires that architects learn to understand and interpret a new class of information that can impact their decisions. This doesn’t mean architects should become engineers. Just like understanding building codes & zoning laws doesn’t require architects to become lawyers, understanding performance of buildings doesn’t require them to become building physicists. The burden lies on universities to introduce architects to performance based design, and technology providers to make software that makes it very intuitive for architects to understand performance impact of buildings they design.
At Sefaira, we believe that performance based design is new reality which differs radically from performance analysis. It should be in the interest of everyone in our industry and beyond to help facilitate this change, and empower architects to move rapidly to the new world of performance based design and much better and more sustainable buildings.