Designing flexible, complex office buildings

Mixed-use office buildings demand a great deal of expertise, flexibility, and complex technology, making them more challenging than one might expect. Engineers with experience handling office buildings share advice and a glimpse into the future.

By Consulting-Specifying Engineer January 16, 2019


Jason Gerke, PE, CxA, LEED AP BD+C, Mechanical & Plumbing Group Leader |, Principal, Graef, Milwaukee

Jason Majerus, PE, CEM, LEED AP, Senior Engineering Leader | Principal, DLR Group, Cleveland

Pui-Yee So, PE, LEED Green Associate, Electrical Engineer, Design Team Lead, Page, Austin, Texas

John Yoon, Lead Electrical Engineer, McGuire Engineers Inc. (MEPC), Chicago

CSE: What’s the biggest trend you see today in office buildings?

Jason Gerke: Besides having open spaces, creating flexible spaces is the next big design goal that we see. Creating spaces that are open architecturally creates challenges for the HVAC design. Open spaces typically have limited ceiling areas for HVAC systems because of designer goals to create the largest volumes possible. Flexible spaces require HVAC systems to handle small heating and cooling loads as well as a large, sudden influx of people requiring immediate responses from building HVAC systems.

Jason Majerus: One of the biggest trends we see is a reduction in area dedicated to traditional open offices and an increase in area of break-out, collaboration, and private-conversation spaces. For mechanical, electrical, plumbing (MEP) systems, this has a significant impact on controllability and system diversity.

Pui-Yee So: There is more emphasis on the wellness of building occupants. People are spending more time indoors at their jobs, and it is more important that their environment contributes to their well-being. This is reflected in an increase of projects pursuing or following the International WELL Building Institute’s WELL building certification or principles.

John Yoon: The greatest trend is not necessarily in the systems that we specify but in how commercial offices are used, with the continued blurring of the lines between traditional work functions and social life. The focal point of most repositioning projects continues to be shared amenity spaces (bars/restaurants, fitness centers, Wi-Fi lounges, game rooms, etc.). The costs associated with constructing and maintaining these types of amenities are dramatically higher than those of a traditional office environment, and the building owner typically doesn’t get any direct revenue from them. While it is debatable whether these types of spaces are just a passing fad and/or economically sustainable in the long run, it is difficult to compete in the commercial office market without them.

CSE: What trends do you think are on the horizon for such projects?

Yoon: These amenities seem to be intertwined with the perceived societal preferences of millennials—the generation making up the core of the workforce. As long as the job market remains tight, they’ll probably continue to be included in new construction and major renovation. However, they impact the property owner’s bottom line. The question is if there is a downturn in the economy and the labor market loosens, will there still be a need to have these types of amenities as a talent retention tool?

So: More “smart buildings” are on the horizon. There will be more controls and integration of all the different building systems to allow the building occupants to “customize” their experiences. HVAC and lighting systems will respond to unique occupants that are detected. Eventually, the building will have the ability to be customized to each individual occupant’s unique needs.

Gerke: I see the amount of glazing increasing in buildings, the available ceiling space decreasing, and the need for buildings to adapt to a multitude of uses. Besides these trends, the interconnected nature of all systems in office buildings, as in many other building types, will increase. These trends will require engineers to thoroughly consider all available options for systems and how those systems interact.

CSE: Are you noticing an increase in the building of new projects versus retrofitting existing buildings?

So: At Page, we work on projects all over the United States, and in terms of the number of projects, we are seeing an even amount of new construction projects and retrofitting existing buildings. The project sizes are much larger for the new buildings. In the Austin, Texas, area (where one of our offices is located), we have noticed many new building projects in the works.

Majerus: We are still seeing the majority of workplace projects as retrofit/tenant-improvement. The pace and budget that these projects are expected to be delivered within generally dictate a retrofit approach.

Yoon: Retrofit/repositioning of existing buildings still dominates the overall volume of work. While the overall quantity of new construction projects is decreasing, the scale of what remains is dramatically larger. Ten to 20 years ago, it seemed like the sweet spot for commercial office construction was centered on greenfield low-rise office buildings between 100,000 and 250,000 sq ft. Now, the same suburban office developments are struggling to fill vacant suites when the tenants are moving to central business districts (CBDs) to be closer to where their workforce wants to live. This mass exodus from the suburbs to CBDs has been going on for at least 5 years. As such, development opportunities with a reasonable return on investment (ROI) in those same CBDs are becoming more limited. With fewer opportunities for that type of urban infill construction, a good portion of the new construction market seems to be focused on the wholesale redevelopment of large corporate campuses and industrial facilities into mixed-use developments. Those types of large redevelopment projects have a high-risk, high-reward ratio—their viability often is tied to the availability of TIF money from the local municipality.

Gerke: We are absolutely seeing an increase in new construction versus remodeling of existing structures in our area. The market is hot in Milwaukee and the Midwest right now. New construction is all about creating iconic buildings again, after what we saw as a decline in new construction for a number of years during the Great Recession. Conversely, we do have a number of projects that are repurposing existing structures; many times they are historic buildings. These buildings are being repurposed based on ideal locations or unique features that will help in the recruiting/retention process of staff.

CSE: Tell us about a recent project you’ve worked on that’s innovative, large-scale, or otherwise noteworthy. Please tell us about the location, systems your team engineered, key players, interesting challenges or solutions, and other significant details.

Gerke: Within the past year, our team completed the construction phase of an office building for Milwaukee Electric Tool Co. This new building was a 4-story, 200,000-sq-ft structure that was designed with features to mock a construction site, where their products are used. Designing HVAC for a building with exposed structure throughout and bare metal sounds easy, because who cares if the HVAC is visible. However, the systems needed to be extremely quiet to meet owner’s project requirements in addition to being highly efficient. Further, the latest technology was desired by the client, so the design team incorporated the latest air-cooled chiller technology and fan-array systems in the main air handling units (AHUs).

Majerus: Enhanced air quality and increased outside air for improved productivity is a trend that we are seeing as an “ask” from some of our clients. One recent project we worked on used this as a way to inform system selection. The client asked that we provide two times the amount of outside air required by ASHRAE 62: Ventilation and Indoor Air Quality, due to the research showing increased productivity as a result of increased outside air. In combination with this request, our goal was to reduce energy consumption. We reviewed numerous options, of which an active chilled-beam system was one; this would inherently require more than ASHRAE 62 minimum outside air to serve as the required primary air required to meet latent cooling loads. This system would also reduce fan energy consumption by moving from a traditional mixed-air variable air volume system to a dedicated outside-air unit with zone-level active chilled beams.

So: We recently worked on a master plan for the Texas Facilities Commission consisting of two high-rise office buildings located in downtown Austin, with an interconnecting underground garage and aboveground green “mall” space. The systems our team engineered included (but were not limited to) the following concept design systems: mechanical HVAC, plumbing systems, fire protection systems, electrical power system distribution, lighting system, lighting control systems, and telecommunication infrastructure. One unique challenge of this project was the phasing of all the different components and the division of systems as well as metering of electrical power. The project consists of a total of six different phasing packages to be bid out to different design-build teams. The project will change the landscape of Austin’s downtown core area and environment by providing green space for the public and all office building occupants in the district to gather and enjoy.

CSE: How are engineers designing office facilities to keep costs down while offering appealing features, complying with relevant codes, and meeting client needs?

Gerke: Wisconsin and a few other Midwestern states historically have lagged behind in energy code updates until this year—they are now using the 2015 version of the International Mechanical Code. Prior to this time, the lax codes have allowed teams to make decisions to save construction cost and sacrifice energy use over the life of the building. Even back then, there were ways to be creative in sizing and laying out systems while maintaining energy efficiency.

So: We work closely with our clients to prioritize their needs and space functionality and balance them with the project budget. We have noticed an increase in projects where the owners bring the contractors on board earlier—this results in multiple points during the design process for contractor costing estimates to ensure that the project is still on budget. Using BIM allows us to maximize spaces, which results in more efficient designs and reduces costs from Day 1 through construction. Ultimately, the buildings are more efficient and easier to control, thus reducing the overall operational costs. Our engineers look for creative design solutions and continually learn about new technologies or products. We attend vendor lunch-and-learns or seminars. Our teams conduct post-occupancy lessons-learned sessions with the contractors, owners, and occupants. Our teams also take advantage of tours of other firms’ buildings to learn what went well and what didn’t go well. We take all these opportunities to understand the lessons learned and apply them to our next projects. It also helps that the cost of LED lighting and lighting controls have come down significantly in the past few years.


CSE: How has your team incorporated integrated project delivery (IPD) or virtual design and construction (VDC) into a project? Define the owner’s project requirements and how the entire team fulfilled them using these methods.

Majerus: Our team has been using virtual reality (VR) during the design process, most notably during design reviews with our clients. It really helps to convey the design intent to folks that are not used to reading 2-D plans. We see this as a powerful tool that will become commonplace and part of the design process for most projects.

So: Many of our projects follow the IPD process, where the owners, contractor, and our design team work closely together to deliver projects. The development of new technologies allows the building design and construction team to coordinate better and to maximize energy efficiency opportunities between systems. Early in the design process, we provide BIM for all parties involved. This allows the team to meet with the owner to establish project goals. The client experience is enhanced and the projects are more likely to stay on budget and schedule. This level of collaboration and coordination continues for each major design milestone, ensuring the contractor prices the design drawings and provides possible value-engineering items. The design team and owner review and evaluate value-engineering items against the project requirements and implement changes into the next package.

Gerke: Our company has been involved in projects with early contractor participation. These projects have not technically been contracted as IPD, but many of the same practices have been incorporated. We have participated in this type of project delivery on complex design and construction projects where there are many unknowns related to ultimate needs and schedules. Another prime project type for this delivery method, in our experience, has been reuse of an existing building with a tight schedule. In these instances, we have been contracted by owners directly for design and were told/asked/assigned to work with the general contractor or construction manager and their trade partners. The relationships may be somewhat forced at the initial announcement, but early and open communication by the team members is a required process for a successful project, with cooperation from concept design to final commissioning.

CSE: How are office buildings being designed to be more energyefficient?

So: Building automation systems (BAS) play a significant role in any energy strategy for a building. Techniques such as supply-air reset, free cooling, and night setback/morning warmup strategies have been implemented for years. Newer trends will leverage system interoperability between dissimilar systems and inexpensive Internet of Things (IoT) sensors communication—for example, conference rooms. A Windows-based room scheduler can be used to schedule a meeting. Just prior to when the meeting is scheduled to start, the lighting control system turns on the lights, the audio/video system powers up the overhead projector or flat panel, the BAS adjusts the temperature in the room based on the number of people accepting the meeting invitation, and the shading control system will close the window shades for rooms located on a perimeter wall. All these systems must communicate with one another via standards currently under development by the Telecommunications Industry Association (TIA). This concept will be further developed and refined via the smart communities and smart cities initiatives.

Yoon: Ideally, you would first address passive measures, such as improving the thermal performance of the building envelope. However, this is typically not an option for existing buildings. To make matters worse, the MEP infrastructure in many existing buildings has insufficient capacity to support that increased level of occupancy that we are seeing in a modern commercial office environment. Without wholesale replacement of equipment, the question is how do we efficiently adapt MEP infrastructure in existing buildings to accommodate increased density? Ideally, we would like to replace older equipment, but that is difficult to justify to a client without an attractive ROI (5 years or less) or specific code requirement. Often, the best solution is to improve the controllability of what you currently have and to be able to more accurately sense interior conditions. Integrating occupancy sensing and carbon dioxide monitoring into direct digital control (DDC) systems are potential solutions to more effectively use the capacity that you do have. That doesn’t improve the efficiency of the equipment itself, but it can help control overall energy usage.

Gerke: Office buildings, similar to many other building types, have opportunities to incorporate a variety of energy-efficient features. Important items to consider are efficient air-cooled or water-cooled chillers, hot-water heating systems to integrate multiple boiler styles and recover heat for available processes, and air handling systems to balance the ductwork pressure drop with the first cost for ductwork sizing. An air handling system with lower (reasonable) air pressure loss, highly efficient direct-drive fans in a small motor-array arrangement, energy recovery where it makes sense, and control systems that alert building operators when systems deviate from historical parameters are all very reasonable and practical features to incorporate. These system features are nearly standard by most manufacturers and are familiar to many operators. However, these systems are not typically all combined into one facility to maximize savings.

CSE: What is the biggest challenge you come across when designing office buildings?

Gerke: Many times, the space for air handling systems is restricted in these types of projects. A square foot of floor used for an air handler is a square foot of floor that is not leasable by the building owner. The height of a building is affected by the required space above a ceiling. Adding 6 in. or 1 ft to the floor-to-floor height could increase the construction cost for the façade to an unacceptable amount. Space for HVAC systems is the most challenging requirement to overcome in the design phase for many engineers.

Majerus: Currently, there is a large number of renovations and tenant-improvement remodels occurring in the office building environment. For these types of projects, the biggest challenge we see is dealing with knowns and unknowns that lie outside of the project-scope boundary. Budgets may not support whole upgrades to building infrastructure, and modifications to existing infrastructure become difficult, as these systems have typically been modified over time as spaces are built out, customized, remodeled, subdivided, occupied, expanded, etc. Documentation for these modifications may not exist, and there may be other work planned—ongoing or in the future—that the design team is not aware of. Even if the new space is simple and straightforward, a significant effort may be required to understand the existing conditions and the required improvements to the building infrastructure to realize the goals of the project.

So: The biggest challenge is fighting for physical space for our MEP systems within the building. With the LEED requirements, the mechanical AHUs tend to be physically bigger in size to accommodate the additional air changes, and the electrical systems need more room for splitting up panels for metering purposes and for control panels. Every square foot of space counts for an office building, so owners can generate rent, so it is a challenge to get the room we need for our equipment.