Engineering in K-12 schools
CSE: Please explain some of the general differences between retrofitting an existing school and working on a brand-new structure.
Hammelman: The biggest and most obvious difference is retrofitting is constrained by the existing building construction. This factor will often influence or even dictate the system we can install. For example, many schools built in the mid-1950s and 1960s have a very low floor-to-floor height and minimal roof structure, which limits HVAC systems choices. With new construction, the sky—well, really the budget—is the limit. Engineers can work early and in tandem with architects to determine the optimum building layout for the client’s preferred HVAC system needs.
Roy: Retrofitting an existing school requires a preliminary existing conditions assessment that will provide the designer with a baseline for what the existing building is capable of and whether new systems can be additive to the existing or stand-alone with brand new utilities if the infrastructure cannot support the new systems. Many times, the design effort is greater for retrofits due to working around existing conditions and limitations that are exposed as part of the existing conditions assessment. However, these projects also give the designer greater insight into the maintenance and operating capabilities of the school and allow the designer to customize the design based on how he or she can expect the school to realistically operate. With new construction, designers have a clean slate to work with, although there are greater demands to establish the utility infrastructure to serve the school.
Jefferson: In any of our projects, we work diligently to first try to reduce the heating and cooling loads and find passive opportunities before we jump to active systems (HVAC, lighting, etc.). Existing buildings are usually tougher to make changes to, like upgrading the envelope. But we’ve found some of our very old building retrofits to actually be much easier to retrofit than some from the last 30 to 50 years. Before energy and artificial lighting got cheap and available, those original designers set up their projects to take advantage of daylight and natural ventilation.
Najafi: Retrofitting existing schools poses a different set of challenges, which requires a different design approach. When retrofitting existing facilities, we must consider the age and condition of existing MEP infrastructure and analyze the feasibility of re-use with regard to energy and cost efficiency. We conduct a lifecycle cost analysis of the existing systems in comparison to the new systems to determine whether renovation of the existing systems or a complete replacement is in the client’s best interest. Improving the energy efficiency in existing buildings also requires a thorough analysis of the building envelope: windows, walls, insulation, etc. We analyze both the feasibility and the cost of replacement versus adding insulation and vapor barriers to existing walls to determine the impact the reduction in HVAC loads will have on energy savings.
The constrained spaces most existing MEP systems are located in add another level of complexity when compared to new building design and must be coordinated closely. A new structure also requires analysis of envelope, lifecycle costs, and coordination, but an existing building brings that analysis to another level: there are some mechanical systems that just aren’t feasible in retrofit buildings because of the space required; and insulating existing walls is more difficult and can be more costly in a retrofit than in new construction. To provide highly efficient, cost-effective systems in renovated facilities requires first-hand knowledge of the systems on the market, and the creativity to adapt to the constraints of an existing facility. Although both new construction and renovation projects require creativity, new construction projects have a different design approach because they are more flexible.
Hedman: When designing for an existing building, engineers must pay close attention to the existing infrastructure and determine if there are any limitations in supporting the proposed architectural program. Furthermore, phasing often becomes a challenge; many times the school must continue to operate during construction.
CSE: Many schools require flexible space—building features that can be adapted to different uses as the school’s needs evolve. How do you take such requirements into consideration?
Jefferson: Flex space has to be adaptive to future needs, but even daily needs change. We’re seeing libraries become “media centers” or “multipurpose areas.” We’re responding to that with systems that are adaptable, like multiple levels of lighting, but also are user friendly. The user-friendly concept is really important in these spaces. Unlike a typical classroom with a dedicated teacher, nobody “owns” this space. They need to be able to figure out quickly how to get to the right levels of light for whatever it is that they are doing.
Hedman: Designing for these types of spaces for flexibility is a challenge. Appropriate systems must be designed such that the infrastructure can support program changes with minimal impact.
Roy: Obviously, it is critical to know these requirements as early in the design process as possible. Generally, looking at the design holistically and understanding the commonalities and differences of the flexible spaces and their design impact allows designing a more generic design in some cases and a more specific design solution in others, depending on the balance of commonalities and differences. We typically combine dining rooms and gymnasium-type multipurpose spaces because they are seldom used fully loaded concurrently and the ventilation loads are similar, allowing the common system to serve both.
Najafi: As engineers, we advocate for smart engineering design choices early in the design process. This means that we work closely with the architect and owner to understand individual space usage within the building, building schedules, design approach, capability of owner’s maintenance staff, owner requirements, and so forth. Understanding the intricacies of how each individual space will be used and the scheduled of use prior to ever submitting a schematic design is a huge part of this. With this kind of information, the MEP systems can be integrated into the architectural design very early on to provide systems that work with the building instead of against it.
Many schools are used as mixed-use spaces where the community has access to the spaces both after hours and during the summer months—and when it comes to schools, no two schools are alike and no two spaces within a school are alike. Understanding how a school is going to be used throughout the year is important if we are going to work modularity and flexibility into the mechanical systems.
If, for example, only 20% of the school is being used, the base building systems need to reduce to 20% of the load to realize energy savings. When using geothermal and water source systems, we need to have enough pumps with variable frequency drives (VFDs) to provide appropriate turn-down on the water side. With air-cooled systems such as packaged rooftop units for gymnasium spaces, we often need to provide single zone variable air volume systems with demand control ventilation so that the system functions appropriately when the space is in full use, but can also reduce their energy use when the spaces are not fully occupied. An intricate and early understanding of the building gives us the ability to design systems with modularity and flexibility to meet the ever-changing demands of a K-12 school.
Oathout: The requirement for flexible spaces that differ from traditional classrooms is a growing trend in K-12 facilities. Communication with the users and the full design team is the key. DLR Group uses an integrated design process that includes the engineering teams very early in the process so expectation from the users can defined and developed well in advance of the detailed design. Once the use of a space use is understood, an efficient, flexible, and robust system can be selected that will likely be different than what was designed 20 years ago.