Performance based design is an approach to complying with the code or developing alternative compliance using engineering principles. Most commonly, performance-based design is used to evaluate the smoke control system within an atrium, determine the egress time of a building or assist in the sizing of stairwell and elevator pressurization systems. Typically, mechanical engineering firms will utilize hand calculations in order to estimate the total exhaust rate for a smoke control system. Using this one-size-fits-all approach, there are multiple inefficiencies that can be caused on the project.
Performance-Based Design
Hand Calculation vs. Fire Modeling
Hand calculations do not take into account the characteristics of the space such as building geometry or the location of the smoke plume, exhaust outlets or make-up air inlets. Hand calculations almost assuredly overestimate the smoke exhaust quantity required, which has a domino effect on the remainder of the building systems (i.e. larger fans, larger generator, more make-up air openings in the building façade, door and window openers prone to failure, etc.). All of these items can increase the cost of your project. Sparc can perform computational fluid dynamics models (fire modeling) to accurately recreate the geometry of the space to see how the smoke actually travels and determine the most efficient smoke control approach. In almost all scenarios, preparing a fire model will result in significant financial savings for your project.
Balancing Mechanical Systems
In addition to atria, stairwell pressurization and elevator pressurization systems can be difficult to determine fan sizing. While spreadsheets are usually used to assist engineers in sizing these systems, the accuracy of those documents is greatly reduced when the stairwell pressurization and elevator pressurization systems share a boundary condition with an atrium or some other smoke control system. Through the use of CONTAM, Sparc can help you size these fans while taking into consideration the effects of adjacent smoke control zones. Where the modeling approach is not selected, it can result in undersized fans and the inability to balance the smoke control systems. Either of these conditions results in increased costs and time delays for the project.
Performance-based design can also be used to justify an equivalent level of safety to a code requirement that is difficult for the design team to achieve. The alternative code compliance approach can be used to evaluate insufficient egress capacity or exceeded travel distances, determine the effect of a fire on an exposure due to building separation distance and evaluate alternative smoke detection spacing.
Sparc can provide the following performance-based design services:
- Computational Fluid Dynamics (Fire Modeling)
- Egress Modeling
- Alternative Code Approaches / Developing Equivalent Levels of Safety