How to design medical buildings: Sustainability and energy efficiency
- Randall Ehret, PE, Senior Vice President, Environmental Systems Design, Chicago
- Timothy Larson, PE, LC, LEED AP, Principal, RTM Engineering Consultants, Milwaukee
- Melisa Rodriguez, PE, SET, Director of Fire Protection Engineering, LEO A DALY, Minneapolis
- Matt Volgyi, PE, LEED AP, Principal Engineer, Southland Engineering, Garden Grove, Calif.
- Mike Zorich, PE, LEED AP, Associate Principal, IMEG, Rock Island, Ill.
CSE: What unusual systems are owners requesting that help save energy and/or electricity when a space is unoccupied?
Volgyi: In intermittently occupied spaces, occupancy sensors that turn off lighting and turn down the air conditioning systems can save a lot of energy. Reducing the supply air may be challenging in health care buildings, as maintaining room pressurization may not be possible without return- or exhaust-air volume control. You can still save energy by resetting the room temperature requirement or simply closing the reheat valve during unoccupied hours.
Ehret: We are gaining more interest from our health care facilities for a quality continuous commissioning program.
CSE: Energy efficiency and sustainability are frequent requests from building owners. What net zero energy and/or high-performance systems have you recently specified in such facilities (either an existing building or new construction)?
Zorich: We designed two of the largest lake-coupled geothermal health care projects in the world. Both serve inpatient health care facilities. The most efficient, Great River Medical Center (GRMC) in Burlington, Iowa, has an actual energy-use intensity (EUI) of 96 kBtu/sq ft/year. Advocate Sherman Hospital (ASH) in Elgin, Ill., has an actual EUI of 188 kBtu/sq ft/year and water use of 20 gal/sq ft/year (an average facility is around 70). A typical ASHRAE 90.1 baseline facility is expected to have an EUI between 200 and 225 kBtu/sq ft/year. GRMC incorporates VAV as its primary means of conditioning while ASH’s design includes distributed water to air heat pumps. A variety of operational and occupational conditions account for the difference in energy use between the two facilities, but both pursued a progressive system that is producing great energy results.
Volgyi: We have not come across a health care project so far with net zero energy use. Due to the significantly higher energy use of such buildings, providing a net zero facility would cost significantly more than it would for other building types. We have designed several health care buildings with LEED Silver classification and 16% to 20% energy savings over ASHRAE 90.1, which still carries a cost premium but provides a payback. Be cautious with payback calculations. To achieve these levels, features with a 10- to 15-year payback will oftentimes need to be incorporated, which will significantly add to the project cost and impact return on investment.
CSE: What types of sustainable features or concerns might you encounter for such a facility that you wouldn’t on other projects?
Zorich: With any cutting-edge system at a health care facility, whether it is considered sustainable or not, you will encounter two major concerns. First, is the system reliable and able to operate 24/7? And second, does the system have the potential to have a negative impact on infection control? This is why systems such as natural ventilation, greywater reclamation, and others are not common in health care facilities.
Volgyi: Actually, the systems we have considered and used are similar to systems used on other building types.
CSE: What types of renewable or alternative energy systems have you recently specified to provide power for such projects? This may include photovoltaics, wind turbines, etc. Describe the challenges and solutions.
Volgyi: We have considered a variety of these options and have used photovoltaic systems, solar water heating, and cogeneration equipment where appropriate. The challenge is often the project budget, as all these systems are relatively high-priced items with long payback, which means they are often the first to get value-engineered out—most of the time for valid reasons.
CSE: What are some of the challenges or issues when designing for water use in such facilities? What types of low-flow fixture, water reuse, or other techniques have you designed?
Volgyi: Hand-washing is such a critical element for infection control that using low-flow fixtures will have to be handled with extra care.
CSE: How has the demand for energy-recovery technology influenced the design for these facilities?
Volgyi: Energy recovery is often considered to achieve the energy targets of these projects. Runaround heat-recovery systems work well for 100% OA systems located in the right climatic condition. Enthalpy wheels, due to potential cross-flow and infection-control concerns, need to be carefully considered. Heat recovery for boiler flues or heat-recovery chillers can be good applications due to the high hot-water use in these buildings.