Using the AEDG in large hospitals

To achieve energy efficiency in a hospital, engineers should fully understand the Advanced Energy Design Guide.


Learning objectives

  1. Understand the goals and objectives of the Advanced Energy Design Guide (AEDG) for Large Hospitals.
  2. Learn how experience gained during commissioning can impact building energy efficiency.
  3. Identify and apply cost-effective energy conservation concepts 

Figure 1: At St. Anthony Hospital in Lakewood, Colo., actual energy usage has been tabulated and graphed, with the AEDG 50% energy use target entered to calculate projected annual energy cost savings. Courtesy: Engineering Economics Inc.To achieve optimal performance levels in a health care facility, the Advanced Energy Design Guide (AEDG) for Large Hospitals is a useful tool (download the ASHRAE AEDGs for free). The process is well laid out, has specific methodologies established per climatic zone, and has energy performance expectations quantified in terms of Btu/sq ft. Energy use is projected to vary from 106,000 to 125,000 Btu/sq ft in geographic zones 1 thru 7 (continental United States) for HVAC, lighting, and receptacle/process loads. Slightly more than 50% of expected energy use in a hospital is related to HVAC systems and equipment and is therefore the focus of this article, followed by the relatively less significant impact of lighting and plumbing, beyond current code.

Other guides for hospitals and health care facilities include U.S. Green Building Council LEED for Healthcare, ASHRAE 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings, and the International Energy Conservation Code (IECC). States may also have various codes; check with the local authority having jurisdiction.

A 50% AEDG energy consumption target is less than half that of conventional hospital consumption—a lofty goal and one that most will say is unattainable. Obtaining usage this low will require pulling out all the stops, and as the AEDG states, employing integrated design practices and applying scrutiny to everything that either directly consumes energy or has an impact on energy use. It will require new practices that all designers and equipment planners will have to take to heart, working collaboratively to reduce loads and, in turn, consumption.

The following is a summary of lower cost/no additional cost design features, but the list should not be considered exhaustive. The AEDG includes additional information, which can be applied in pursuit of the 50% reduction goal. Some items included in the AEDG will require additional funding, and all will take an integrated design approach.

The commissioning process includes the publication of a systems manual. A systems manual is a composite of drawings, technical literature, sequences of operation, and explanation of system operating nuances for operator reference and training. It is not an operations and maintenance manual, nor is it meant as a replacement. The better systems manuals have one-line diagrams, floor plans with equipment locations, and Web links to items listed on the floor plans. If provided in electronic format, the information can be presented with a multimedia format to depict what you have, how it works (generically and as applied), troubleshooting features, and where to get support, parts, or service.

Once the design and construction are complete, the final product will be tested and performance will be validated, but the systems may not perform exactly as planned. Over the years, seasonal testing, revisions to set points, and revisions to operating practices based on system actions, reactions, and interactions may be required. The intent is to obtain the best possible results, short of capital intensive modifications.

The process defined by AEDG starts with project conception, followed by team selection, conceptual design, construction documents, construction, and operation. The following addresses these from an owner’s representative/commissioning perspective:

  • Project conception will be based on owner education, buy-in, and commitment. This should start with owner understanding of health care project design. Site and space planning is first, followed by design narratives provided by each design discipline. The owner’s project requirements (OPR) is assumed by the design team, based on their health care design experience, and is not typically published at the outset. These assumptions may be indicative of the actual project requirements, and must be clarified either prior to or during the earliest stages of project design.
  • The provisions of AEDG may not be known to the project designers. In recent years, health care construction been heavily based on applying the recommendations of the Health care Facility Guideline Institute (FGI), a well-known publication of health care design. While these guidelines define a higher standard for health care design, they do not address energy efficiency. That has to come from elsewhere, and the AEDG for Large Hospitals is a good start.
  • Team selection is similar to interviewing job applicants. On the first go, one will say all the right things. Further investigation and understanding of team dynamics is necessary. Does the design team believe in and practice energy conservation? Do they know the methodologies and apply them in practice? Will the team work interactively and collaboratively? For the team to function collaboratively, they must have the correct chemistry, and the owner’s representative must set the stage for the design team to break with traditional practices, pushing for creativity and energy efficiency, as well as higher performance.
  • Mechanical, electrical, and plumbing (MEP) system over sizing is the most frequent malady of new hospital design. One must understand, from a design perspective, there are no claims for over sizing, as there might be for under sizing. The practice will continue, and with few exceptions, equipment over sizing will be counterproductive to energy-efficient design.
  • Energy-efficient conceptual designs should be documented in a checklist and the OPR. The implications for how one will achieve a 50% reduction per AEDG must be identified and documented. The checklist, similar to a U.S. Green Building Council LEED rating checklist, should be used for planning and design. The owner and the design team should create the checklist with assistance of a third party that is knowledgeable in hospital design, energy-efficiency concepts, cost estimating, and technical feasibility.
  • A thorough review and assessment of project requirements, and AEDG or Energy Star goals, should be completed by the owner and the design team before the design process begins. The next step is the OPR, which must reflect what the owner expects the project to be, reveal the depth and breadth of the planning, and establish the guiding design principles for the project. While the OPR may have some elements of a design narrative, it should clearly state project requirements, to include the form of the project, performance objectives, and in the case of AEDG, energy-efficiency expectations.
  • In addition to checklists and the OPR, the expected Energy Star ranking, or maximum Btu/sq ft, must be identified. Both are tangible and quantifiable, and including them in the OPR is more effective than simply stating a desire for energy efficiency. Ultimately, utility usage will determine both, which can be metered with quantifiable results. Unfortunately, verification will not be possible until one year after occupancy, not while the design is under way.
  • The owner, the third party, and the designers must serve as advocates for the process, and remain active throughout the design with regular discussion and debate. While the designer is usually in charge of the effort, either the owner and/or the third party must have technical expertise to challenge and debate to establish the comprehensive truth of the concept and application. Owner advocacy is not an easy or simple task. It requires knowledge, intuition, communication, and commitment beyond opting for low first cost.
  • Every project has a budget, and all too often it is less than what is needed. Most concepts impact all disciplines, not just MEP systems, and understanding budget limitations during conceptual design may be the most important factor moving forward. How to do more with less is required, requiring knowledge and hard work to get there.
  • Cost implications must be addressed and regularly reviewed as the design progresses. Cost estimating will delineate all the variations, requires thorough knowledge of all the disciplines, and must establish the additions and deductions on a conceptual basis. The cost estimator is usually tasked to estimate based on experience, with only limited design documents upon which to base the estimate.
  • Unfortunately, the construction manager (cost consultant) is usually not familiar with the detail of mechanical and electrical costs, often relying on subcontractors to provide input. During the early stages, the subcontractors are in the queue for the job, with emphasis on having adequate budget for their portion of the contract, absent concern for economy and lower cost alternatives.
  • Computer models are used to predict loads and energy consumption, with the intent to define potential payback prior to or in conjunction with the design. However, computers are unable to conceptualize, and the model is only as good as the experience of the input engineer. The computer will give relative performance data but is unable to predict actual performance. In the HVAC world, there are an infinite number of variables, many of which can neither be modeled nor controlled. While useful, the team must understand the projections are relative, not finite.
  • One must acknowledge that HVAC energy efficiency is more than selecting energy-efficient equipment, motors, etc. It requires a systematic approach to HVAC design and integrated design concepts and application. Lower loads and the use of natural or more cost-effective energy sources will be required. Lastly, operating equipment efficiently, once installed, will yield the energy savings that will last for the life of the systems.

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