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Integration: electrical and HVAC systems

Learning objectives:

  • Understand how building systems can be integrated, such as electrical and mechanical systems.
  • Learn about building management systems and building automation systems.
  • Assess ways to integrate engineered systems to achieve greater energy efficiency in buildings.

Technology has changed the way modern buildings are designed and operated. It has improved the reliability and efficiencies of the modern electrical and mechanical systems. Equipment is more efficient due to advanced component design and the incorporation of onboard computer controls and logic.

Building management systems (BMS) are more advanced than ever and can operate the systems to much tighter tolerances. The improvements have changed the way today’s engineers can design and operate buildings to maximize energy consumption and minimize their impact on the environment.

To achieve these goals, the various building systems must operate together instead of working as stand-alone systems. Integration has compelled electrical and mechanical engineers to work more closely together during the various design phases so they can incorporate the required tools and logic to seamlessly operate the modern smart building.

The integrated design team

For many years, projects were designed by teams comprised of architects and engineers (civil, structural, fire/life safety, mechanical, plumbing, and electrical). This team approach worked well for most projects because the design expertise was contained within the group. The design team was a stand-alone component that had limited exposure with the construction team and the owner once the building was in operation. This relationship is illustrated in Figure 2.

Although each team was coordinating internally, the coordination efforts between the design team, contractor, and owner were disjointed and disconnected. This resulted in buildings that were designed with specific efficiency measures but constructed with systems that were more cost-effective than base design, which resulted in them not operating according to the original design intent. This dynamic needed to change as buildings became more complex due to advancements in technology, building materials, and construction methods. It was necessary for the traditional design team to expand and seek advice from specialized consultants who work for the architect (acoustics, vertical transportation, building envelope, audio/video, security and surveillance, information technologies, etc.) and nontraditional resources that work for the owner.

As building systems become more advanced and energy consumption becomes a prime driver in system design, it is imperative that the systems operate according to the design intent. Building owners have been turning to commissioning agents (CxA; often called commissioning providers, or CxP), energy engineers, and in some cases, various specialized trade contractors to certify the actual system operation meets the design specifications. In the past, these consultants and contractors were typically hired by the owner and operated independently of the design team.

In recent years, however, the various experts have become involved early in the design process and are integral members of any successful design team. This model has become so successful that many engineering firms have hired these consultants and contractors to provide an expanded service offering to their clients. Allowing these specialists to participate in the early phases of design is key to delivering a successful smart building to the owner.

These specialized disciplines can assist the engineers by providing operational feedback during design that can greatly influence how systems are sized, configured, and operated. This feedback can include but is not limited to:

  • Review of sequence of operations to incorporate practical experience
  • Preliminary electrical, heating, and cooling load profiles based on region and building type
  • Estimated energy consumption for proposed systems to identify the most efficient system option
  • Financial models to assist the owner in making informed decisions
  • Review of equipment submittals to assist the engineers in identifying variances
  • Review and analysis of potential value-engineering (VE) solutions proposed by trade partners.

The feedback loop between operations and design allows the integrated team to operate under a different model that includes more communication and coordination throughout the entire lifecycle of the building (see Figure 2). The operation-driven design model facilitates sharing of information between the design team, contractor, and owner. The model produces a building with integrated systems that are operated as they were designed and to peak efficiency. As the building ages, the operational feedback is used to tweak the systems to improve efficiency or identify areas of the building that may require maintenance or upgrades.

Coordination during the design phases

The design effort required to successfully integrate the building electrical and mechanical systems cannot be viewed as a single checkbox in the designer’s to-do list. Integration must be a conscious effort among the various design professionals involved in the project. As each member of the team begins their respective designs, information needs to pass freely from one discipline to the other. Coordination between the engineers must be intentional to deliver the appropriate information at the right time so as to minimize mistakes and prevent wasted effort.

For example, as the electrical engineer begins to conceptualize the electrical distribution system, that engineer will need to understand the impact that the mechanical systems will have on the electrical infrastructure serving the building. What are the estimated equipment loads? Where are the loads located? How does the equipment operate? The electrical engineer can make assumptions based on experience, but will need the input of the mechanical engineer to finalize the design.

As buildings systems become more advanced, collaboration during each phase of design is crucial to the successful delivery of a high-performing building. It is even more critical when design services are provided by multiple firms or the design is dependent on the input from architects and other specialized consultants. To make the collaboration effort meaningful, each member of the design team needs to understand what information is important to the other designers and when it is required.

Schematic design phase

The schematic design (SD) phase of the project is the starting point for every design and is the time where the electrical and mechanical engineers begin to conceptualize the building systems to meet the project needs. The intent of this phase is to investigate various system options and arrive at a clearly defined concept that meets the owner’s objectives. The SD phase defines the parameters that will influence how the building systems are sized and configured.

The concept design is typically conveyed through a basis-of-design (BOD) narrative and large-scale drawings that can demonstrate basic spaces, scale, and relationship of components. Once approved, this concept will guide the engineers through the design evolution of the various building systems.

During the SD phase, the electrical and mechanical engineers begin to investigate different system options that meet the needs of the project. Each discipline starts to perform calculations and develop technical schematics to define the various options.

Expected engineering tasks that require coordination and input from others at this stage are:

  • Review applicable building codes, building certifications (LEED, Green Globes, Energy Star, etc.), and design standards to identify impacts on the proposed building systems.
  • Determine the level of energy performance based on building-use type and define key metrics, such as energy use intensity or power usage effectiveness.
  • Estimate electrical loads for the project and begin coordination with the civil engineer and electrical utility.
  • Estimate mechanical loads (heating, cooling, water, sewer, and gas) and begin coordination with the civil engineer and utility companies.
  • Preliminary sizing of electrical and mechanical equipment.
  • Preliminary sizing of required plant rooms.
  • Preliminary electrical single-line distribution.

Coordination efforts between the various disciplines should begin to ensure that the proposed systems can integrate. At this point, much of the coordination is kept within the mechanical, electrical, and plumbing (MEP) design team. Critical information required to preliminarily size the electrical and mechanical systems include:

  • Estimated electric loads for the major mechanical equipment (chillers, cooling towers, pumps, air handling units, large fan systems)
  • Estimated heat-rejection rates of major electrical equipment (substations, transformers, uninterruptible power supplies, also known as UPS)
  • Preliminary locations of major electrical and mechanical equipment
  • Available power and voltage
  • Estimated UPS and generator loads (if applicable).

Design development phase

The design development (DD) phase of the project expands upon the concepts developed in the SD phase. The design-team members begin to focus more time on developing the technical aspects of the building systems and material specifications. At the same time, open issues identified at the completion of the SD phase can now be addressed and resolved.

The refinement of the system concepts and increased coordination help to minimize the possibility of major system revisions during the next phase of design. During this process, the relationship between each system and its spatial impact on the design is defined. The owner is now able to start envisioning what the project will look like when complete and how it will function. While most design issues should be resolved by the end of the DD phase, some will continue to be refined, resolved, or modified during the subsequent phases of the project.

The DD phase also is the point in the design where coordination efforts expand beyond the electrical and mechanical engineers to include the CxA and the energy engineers. The entire design team reviews the various system concepts, preliminary control diagrams, and sequences of operation. Preliminary load profiles are defined for the building to assist with preparing electrical, heating, and cooling loads. Based on this information, system modifications are made that will enhance the performance of the equipment and maximize energy savings.

The anticipated deliverables at this stage will include an updated BOD document, drawings of appropriate scale to convey the more detailed level of coordination and outline specifications that begin to define the quality level of the materials and system components. It also is important to note that many of today’s projects use these deliverables to produce preliminary construction-cost budgets or lock contractors into a guaranteed maximum price. At this point, it is imperative that each discipline is coordinating and disseminating the correct information to the entire design team.

During the DD phase, the electrical and mechanical engineers select the systems that best fit the function of the building and start to incorporate more detail into the technical design. Each discipline refines load estimates, calculations, and equipment sizing and develops plant-room layouts and system layouts. Expected engineering tasks that require coordination and input from others at this stage are:

  • Review proposed system design is in accordance with applicable building codes, building certifications (LEED, Green Globes, Energy Star, etc.), and design standards.
  • Define energy efficiency measures and incorporate them into system design.
  • Refine electrical-load estimates for the project based on the chosen design, and continue coordination with the civil engineer and electrical utility.
  • Refine mechanical-load estimates (heating, cooling, water, sewer, and gas) for the project based on the chosen design, and continue coordination with the civil engineer and utility companies.
  • Refine electrical and mechanical equipment sizing based upon selected system design.
  • Finalize plant-room sizing and layouts.
  • Develop system layouts detailing major horizontal and vertical infrastructure (ductwork, piping, conduits, bus ducts, etc.) pathways.
  • Refine electrical single-line distribution.
  • Develop BMS and metering control sequences and control diagrams.

Coordination efforts between the various disciplines intensify as more detail is incorporated into the design of the systems. The DD phase is also the start of coordination with the specialized consultants. Their input at this stage helps the design team to identify system modifications required to incorporate the technology that makes today’s high-performance buildings efficient and environmentally friendly. Information critical to continue coordination and integration of the electrical and mechanical systems include:

  • Revised electric loads for the major mechanical equipment (chillers, cooling towers, pumps, air handling units, large fan systems) and preliminary loads for secondary mechanical equipment (fans, fan coils, terminal boxes, heat pumps, split systems, dampers, etc.)
  • Revised heat-rejection rates of major electrical equipment (substations, transformers, UPS) and preliminary heat-rejection rates for low-voltage and information technology (IT) equipment
  • Revised locations of major electrical and mechanical equipment and preliminary locations of secondary electrical and mechanical equipment
  • Revised UPS and generator loads (if applicable)
  • Identify life safety equipment locations and power requirements.
  • Preliminary electrical-, heating-, and cooling-load profiles based on project-specific criteria
  • Preliminary BMS and metering control sequences and control diagrams
  • Preliminary electrical loads and locations for direct digital control (DDC) panels and devices
  • Preliminary energy modeling (if applicable).

Construction document phase

The construction document (CD) phase of the project is the culmination of the design effort. It is the point in the process where the engineers address the remaining outstanding issues and evaluate the proposed VE options presented by the contractors. If value-engineering options are proposed, the design team can evaluate the options and coordinate with the other disciplines to make sure a mechanical VE option does not adversely affect the electrical design or cost. This information, along with all the concepts and comments from the previous phases, is compiled into the final system design.

The engineers will provide detailed information about the technical aspects of the overall systems and the specified equipment that set forth the requirements for the construction of the project. During this process, the relationship between each system and its spatial impact on the project is finalized. The design team is tasked with coordinating the final design information between disciplines to ensure that all project requirements are satisfied. Coordination becomes even more important within the last few weeks of the design schedule to identify last-minute changes and the impact these changes may have on the designs of the other disciplines.

As the CD phase progresses, the role of the CxA and the energy engineers becomes more critical. This is the last opportunity for the design team to incorporate comments and suggestions based on a review of system concepts, control diagrams, and the sequences of operation. This feedback, usually based on operation experience, allows the designers to modify the systems with the appropriate technology and components required to achieve the proposed building performance. The system enhancements will make it possible for the building owner to control the building systems and collect analytical data to provide real-time feedback to the BMS. Without this operational feedback, the BMS cannot adjust system performance to achieve the anticipated performance and predicted energy savings.

The anticipated deliverables at this stage would include a final BOD document—drawings of appropriate scale that set forth the detailed requirements necessary for construction, and final specifications that define the requirements of the building materials, equipment, and systems. When the construction drawings are complete, the client will have sufficient information to secure contractor bids, obtain the required permits, and ensure that the contractor is building the project as the design team intended.

During the CD phase, the electrical and mechanical engineers complete the system design and incorporate final technical details. Each discipline finalizes load estimates, calculations, equipment sizing, plant-room layouts, and system layouts. Expected engineering tasks that require continued coordination and input from others at this stage are:

  • Perform a final review to ensure the system design is in accordance with applicable building codes, building certifications (LEED, Green Globes, Energy Star, etc.), and design standards.
  • Evaluate final energy efficiency measures and verify all components and modifications are incorporated into the final system design.
  • Calculate final electrical loads associated with the system design and verify that the system is fully coordinated with the civil engineer and electrical utility.
  • Calculate final mechanical loads (heating, cooling, water, sewer, and gas) associated with the system design and verify systems are fully coordinated with the civil engineer and utility companies.
  • Finalize the electrical and mechanical equipment sizing based upon final load calculations.
  • Finalize plant-room sizing and layouts.
  • Finalize system layouts detailing major horizontal and vertical infrastructure (ductwork, piping, conduits, bus ducts, etc.) pathways as well as all secondary and branch pathways.
  • Finalize electrical single-line distribution.
  • Finalize BMS and metering control sequences and control diagrams.

Coordination efforts between the various disciplines and specialized consultants continue as the design of the systems are finalized. At this stage, most of the systems are fairly defined and only require minimal modifications. The design should be nearing completion, and it is important that the communication between the disciplines and specialized consultants does not stop. Information critical to continue coordination and integration of the electrical and mechanical systems include:

  • Final electric loads for the major mechanical equipment (chillers, cooling towers, pumps, air handling units, large fan systems) and secondary mechanical equipment (fans, fan coils, terminal boxes, heat pumps, split systems, dampers, etc.)
  • Final heat-rejection rates of major electrical equipment (substations, transformers, UPS), low-voltage equipment, and IT equipment
  • Final locations of major and secondary electrical and mechanical equipment
  • Final UPS and generator loads (if applicable)
  • Final electrical loads and locations of the life safety equipment
  • Final electrical-, heating-, and cooling-load profiles based on project-specific criteria
  • Final BMS control sequences and control diagrams
  • Final electrical loads and locations for DDC panels and devices.

Bid and construction administration phases

The importance of the bid and construction administration (CA) phases is sometimes overlooked by the design team. In most cases, the design teams have limited exposure during the construction phase. The design-team involvement is usually limited to review of contractor shop drawings, response to contractor requests for information, perform a limited quantity of onsite observation visits, and address issues related to design as the systems are installed.

However, there is a unique opportunity for engineers to provide value to the owner during construction through continued coordination of the design. The engineers become guardians of the design during the bid and CA phases. The design team can work with the owners to de-scope the contractor bids and make sure that the integrity of the design is maintained. The design team can work with the CxA to implement the coordinated design that was agreed upon during the DD and CD phases.

Modern owners and developers are pushing the limits of building design and challenging today’s engineering professionals to become more creative with system design. The demand to bring projects to market quicker and more cost-effectively is reducing the margin of error during the design phase. Engineers must place more emphasis on effective communication and increased coordination between the disciplines to deliver a fully integrated building. Thorough coordination of the design has never been more critical.


Hans Grabau is executive director of mechanical at NV5. His expertise is in multiple market sectors including large mixed-use gaming and hospitality projects, mixed-use commercial developments, mission critical facilities, and central plant design both domestically and internationally.

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