Designing, enhancing office buildings: Automation and controls
Office buildings might seem like relatively simple structures, but engineers with experience in the field know differently. Building automation and control systems must be carefully designed.
Christopher Arnold, PE, Vice President, Wick Fisher White, Philadelphia
Saied Nazeri, PE, CPD, LEED BD+C, Senior Vice President, WSP | Parsons Brinckerhoff, San Francisco
Reardon D. Sullivan, PE, LEED AP, Principal, WFT Engineering Inc., Rockville, Md.
Jill Walsh, PE, LEED AP, Principal in Charge of Mechanical Engineering, OLA Consulting Engineers, Hawthorne, N.Y.
Michael Walsh, Project Manager, PEDCO E&A Services Inc., Cincinnati
CSE: When working on monitoring and control systems in office buildings, what factors do you consider?
b The primary concern for monitoring and control systems is occupant comfort followed by serviceability. The monitoring and controls system should result in improved environmental conditions for the tenant and allow the building maintenance staff to quickly and accurately troubleshoot and repair any possible issues. The building monitoring and control systems are becoming Web-based. This allows tenants to have control over their environment and allows owners to bill tenants for their specific energy use.
Arnold: Among the factors that we consider when working on monitoring and control systems for office buildings are the open areas with variable occupancy that we can design with CO2-based, demand-controlled ventilation, and the enclosed rooms that we can design with occupancy-sensor-based, demand-controlled ventilation.
Michael Walsh: The monitoring and control system should have an intuitive user interface and ideally be end-user configurable. Many owners and operators also request an open protocol to allow ease of integration with different controllers and applications. If the client has an operations staff, it is imperative to get their input during the design phase so they have a high level of understanding of what will be delivered as part of the project. They must be comfortable with the system and confident in the manufacturer's local support staff.
Nazeri: We consider the specific needs of the client and the project on day one and in the future. We support and specify native BACnet protocol systems. We do projects all over the world. We need to evaluate factors such as the local market, the local direct digital control (DDC) providers, service capability, and track record of local providers. We have the capability to design converged network systems should the client want to pursue this option.
CSE: What types of cutting-edge sensors, biometrics, or other controls are you specifying in office buildings?
Michael Walsh: With the more open office concepts clients are moving to, there are fewer interior walls. Therefore, we are designing and implementing wireless temperature sensors to give the client more flexibility with their open-office space.
Arnold: One type of advanced sensor that we specify for office buildings is a dual-technology occupancy sensor.
CSE: What types of metering, submetering, or other systems have you specified for office buildings? Describe a recent project.
Michael Walsh: A trend we are beginning to find with clients is the desire to monitor the actual utility usage for tenants or even individual business units within a company. The standard way of charging for leased office space typically involves some level of cost/square foot of tenant space. With less expensive quality metering now available, we can use temperature sensors and flowmeters to not only submeter water and power usage in portions of a building, but also the Btus used for the HVAC system within a portion of the facility. We have set up a system as described above for a large Cincinnati company with millions of square feet of office space where they charge individual business units based on their actual energy usage.
Nazeri: Pro-rated energy costs are not attractive to many tenants these days. Tenants or end users want to pay for what they use. We see more submetering of lighting and plug-load panels as well as condenser, chilled, or hot-water flow rates in both commercial and residential buildings.
Sullivan: Submetering of office spaces is taking a lead from the data center world in regard to branch-circuit metering. Detailed metering has become standard and is becoming codified within the commercial market. Products like Square D PowerLogic panels will allow granular monitoring of power consumption and ultimately billing of energy consumption. It can be more cumbersome to add the metering to older buildings, as the meters take space that was not programmed for them, and the cost may become prohibitive.
CSE: What are some common problems you encounter with building automation systems (BAS) in office buildings?
Arnold: One issue that we face with office BAS is terminal BAS controllers that rely on the BAS network controller/router for scheduling versus an internal schedule, which becomes a problem if BAS network communication is interrupted or lost.
Jill Walsh: When working in an office building, one of the first things for the tenant's engineer to ask is "Does the landlord have an existing controls system that the tenants need to use?" It is imperative for the engineers to understand the constraints of the system and how they are expected to communicate with that system. Problems arise when any tenant-purchased equipment cannot communicate directly with the landlord system without the addition of panels and programming. If the landlord's system is not understood by the engineer, and the necessary gateways are not included on the contract documents, a change order will occur during the construction phase. There can also be complications in instances where existing HVAC units that serve only the tenant space have separate controls from the base-building perimeter heating-system controls. This can cause the two systems to fight one another, resulting in simultaneous heating and cooling.
Nazeri: Most common problems we see include a lack of quality and timely service during testing and balancing, commissioning, and post-occupancy. High-performance design strategies are often not well-understood by controls technicians, who often try to employ standard and conventional controls solutions.
Michael Walsh: The BAS must have proper planning during design to provide a sequence of operation that can be easily understood and executed by the programmer, and also be understood by the operations staff that will run the facility. Finally (and often overlooked), ongoing maintenance must occur with the BAS to ensure the building continues to operate as designed. During an energy audit or retro- or re-commissioning, we have witnessed many instances where the owner's operations staff have manually overridden controls due to either a lack of understanding of the system's designed functionality or because parts of the system no longer operate as intended. Examples include out-of-calibration sensors and nonfunctioning dampers or valves.
Sullivan: The problems that we see are typically broken into two categories: failure of older systems and lack of commissioning of the new systems. Many of the older BAS are aging past their useful life and have not been properly maintained. Building engineers are not able to properly use these systems to troubleshoot problems, and the tenants are not able to get the level of comfort that they need. We often suggest that tenants negotiate upgrades to the BAS into their lease, including terminal unit points, base-building operating points, and energy-consumption points. We find the keys to proper operation of the new BAS are keeping them simple but effective, understanding the operation of the systems, and commissioning. A BAS is only as strong as its weakest link, and if the system does not properly monitor or control as designed then expectations are not met. Having an independent entity back-check the operation of all points in the system will ensure that the system operates properly.
CSE: What types of system integration and/or interoperability issues have you overcome, and how did you do so?
Nazeri: Not all open-protocol systems are truly "open." It is essential to review the fine details when integrating a tenant system into another open-protocol core-and-shell system.
Sullivan: When a building owner looking to save costs has a new BAS overlaid over an older pneumatic or electronic system, this can result in operational and/or interface problems. Again, we find the keys are: keeping it simple but effective, understanding the operation of the systems, and commissioning. The expectations of the final operation need to be clearly understood. Having an independent entity back-check the operation of all points in the system will ensure that the system operates properly.
Michael Walsh: A common issue in major renovations at existing facilities is the integration of two different manufacturers' control systems. The typical way to overcome this issue is to allow the different systems to communicate over a common communication language such as BACnet. Another example is when a building's control system is being replaced in its entirety. When developing options for replacement, the engineer must understand which existing equipment controllers will be compatible with the new system and which ones must be replaced, so it can be accounted for in the construction budget.
Arnold: We haven't had any problems with system integration or interoperability that couldn't be overcome with the addition of the appropriate interface card or gateway.