Specifying systems for new, existing office buildings
Office buildings might seem like simple structures from the outside, but engineers engaged in such projects know they can be highly complex, with specialized fire/life safety requirements, laboratory spaces, and other unique needs.
J. Patrick Banse, PE, LEED AP, Senior mechanical engineer, Smith Seckman Reid, Houston
Robert Ioanna, PE, LEED AP, Vice president, Syska Hennessy Group, New York City
Douglas Lacy, PE, LEED AP BD+C, Senior associate, ccrd partners, Dallas
CSE: What sorts of challenges do office buildings pose that you don’t encounter on other projects?
J. Patrick Banse: Many challenges involve the way the space is built out. Designing a shell and core space along with finished-out public spaces from HVAC systems that serve both the proposed tenant space and the finished public space—how does this work, and can it be controlled? Also, providing for the need of 24/7 cooling in elevator controller closets and intermediate distribution frame (IDF) rooms when the building is not yet complete presents challenges.
Robert Ioanna: In office buildings, the building façade characteristics play a very important role in sizing and selecting mechanical, electrical, plumbing (MEP), and fire protection systems. In addition, the height of these buildings often induces a stack effect that can wreak havoc with the ventilation control strategies of buildings. This is particularly true in climates such as the northeast that have both extreme hot and cold seasons.
Douglas Lacy: The corporate office projects we specialize in have a project completion schedule that is usually shorter than our other business sectors. With the exception of retail, office projects are by nature one of the fastest-moving project types. They are heavily influenced by the short-term leasing market and influenced by developer ROI. This often requires design of core and shell construction to start well before a final end-user tenant is identified and their project parameters are fully documented. You must be flexible in your design approach and anticipate current and future needs.
CSE: What type of adaptable or modular office buildings have you helped design recently?
Banse: Modular office buildings generally come complete with single point connections for electrical water and sewer services. These are the easy ones. Others are shell spaces that need interior design along with electrical service size and HVAC requirements for others to build and result in the single point utility connections.
Lacy: The majority of the corporate and medical office projects we work on are developer-driven and can be speculative in nature. Therefore, most buildings must be designed to optimize rentable area ratios and allow for multiple business types to occupy the facilities over their life. The primary focus recently has been in low-rise value offices, such as buildings that have multiple three- or four-story wings in a campus arrangement or attached to a central knuckle or lobby that can have future pods added to the floor plate at a later date. This also influences the types of MEP systems we specify and tends to favor distributed components over centralization.
CSE: How often are you called on to retrofit or retro-commission an existing building, as opposed to designing a new building?
Ioanna: A significant portion of our work is being done retrofitting existing buildings. We have seen building owners and developers using the core of these buildings while replacing all MEP systems as well as the building façade. Retro-commissioning is increasing in popularity as building owners look to save energy costs and if located in New York City to comply with Local Law 87.
Lacy: We are working on multiple tenant improvement and retrofit projects at any given time along with new construction. Tenant improvements and retrofit projects are a constant and ongoing market segment even in periods of slow growth. Most new office construction projects result from the end user-first exhausting the existing building options in the local market or seeking to build a signature building from the ground up.
CSE: When designing a new Class A office building, what have building owners been requesting lately? What’s the newest trend?
Ioanna: The most educated owners are looking to their MEP engineers to become active participants during the initial stages of the project. We have a high-performance building design approach at Syska that begins with the simple geometry/orientation of the building through MEP design construction into operations and maintenance (O&M). Our first mandate is to find ways to reduce HVAC and electrical loads. Second is to use "passive strategies" to cool and power—passive systems such as radiant cooling and natural ventilation. Third, we look to optimize the active systems—the more traditional fans, pumps, chillers, etc. The final step is to figure ways to incorporate renewable energy strategies by implementing solar hot water, photovoltaics, or geothermal where appropriate.
CSE: Please describe a recent project you’ve worked on—share problems you’ve encountered, how you’ve solved them, and aspects of the project you’re especially proud of.
Banse: We designed the finish out of about 60,000 sq ft of shell space on level 10 of an empty building. The space had the capability to be served by four different air systems with about 35,000 cfm of excess air capacity. The solution was to remove one unit (creating added useable sq ft), use one at full capacity, and use the other two at a partial capacity to keep systems operational and serve 24/7 cooling requirements for IDF rooms and similar spaces. Additionally, the short floor-to-floor height and existing conditions required a return air plenum be used with multiple duct paths through and around walls to structure.
Ioanna: We are increasingly being asked to design retrofit office spaces to increase or maximize the occupancy of the building space. In a specific project for a confidential client, it "dense packed" employees by providing fewer office spaces and reducing the workspace per employee. At the same time the client increased the number of teaming, meeting, and small conference rooms. This created many challenges for the building’s MEP systems. The building’s ventilation systems could not support the outside air and cooling load requirements. We designed separate outside air systems that were integrated to the base building system through controls. We augmented outside air as necessary using CO2 monitoring. We converted the overhead air distribution system to an underfloor air distribution system by connecting the base building supply air ducts to multiple air towers supplemented with additional cooling coils.
CSE: Describe your experience in designing an office building using the integrated project delivery (IPD) method.
Lacy: The short timeframe associated with office projects has resulted in most projects employing IPD concepts. While most projects still don’t employ integrated form of agreement (IFOA) or multi-party contracts, the teams assembled are often tasked with an understanding that we must function in an IPD manner. With an IPD approach our projects are able to accelerate construction, issue phased packages, and benefit from constructability and cost control during design to avoid “value engineering” and redesign.