©2012 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 54, no. 6, June 2012.
By Paul Marmion, P.Eng., Life Member ASHRAE
About the Author
Paul Marmion, P.Eng., is managing principal at Stantec Consulting in Vancouver, BC, Canada.
Hospitals, with their high ventilation rates and 24/7/365 occupancy, consume more energy than most other building types. An acute care hospital such as the Abbotsford Regional Hospital and Cancer Centre (ARHCC), a $355 million facility with 300 acute care beds, nine operating theaters, maternity and pediatric services, medical imaging, radiation cancer treatment, and a host of secondary staff and patient services, is no exception. To reduce the amount of energy consumed within this 61 756 m2 (664,736 ft2) facility it was necessary to rethink the typical hospital design practice.
The Private-Public Partnership (P3) process created an integrated team comprised of the funding agencies, the owner, architects, engineers, user groups, contractors and building operators. Their efforts resulted in an acute care hospital that uses 34% less energy than an equivalent code-compliant building, and resulted in an annual savings of $475,000, which during the 30-year contract of the P3 equals $14,250,000 that can be reinvested into patient care.
Under the P3 contract, the hospital’s design had to achieve at least three LEED energy points, which required the hospital’s energy performance to be at least 25% better than the ASHRAE Standard 90.1-1999, code-compliant building. At the time of design, this stipulated target was considered to be challenging for a green field acute care hospital.
To achieve the three LEED energy points and to validate the hospital’s operating energy, many possible ECMs (energy conserving measures) were analyzed by the design team with the assistance of the project’s energy consultant, using contractor pricing and advanced simulation software to achieve the best balance of energy efficiency and cost effectiveness.
The results of the analysis were validated using the project operators own energy database and energy analysis software. In addition to the energy design targets, the P3 contract required that the hospital’s operator establish a “baseline” hospital operating energy consumption cost so that yearly energy billing reconciliations can be made to validate actual operating energy consumption of the hospital. The contract also stipulated associated rewards and penalties based on the results of the yearly reconciliation. These stringent requirements made the energy simulation work critical with real-world consequences. A summary of the initial energy study results is in Table 1.
The hospitals design criterion for the hospital is:
- Heating: 1% outside design temperature = –10°C (12°F) in January;
- Heating degree-days below 18°C = 3100 (5580 degree days below 65°F);
- Cooling: 2.5% outside design temperatures = 29°C (84°F) DB and 20°C (68°F) WB in July; and
- Annual Rain = 1600 mm (63 in.).
When it comes to the energy efficiency of a building, the process starts with a high performance building envelope. For this building, the design used low-e, argon-filled glazing with selective shading coefficients for the control of the envelope’s related heating and cooling loads. This is complemented by an energy-efficient lighting system with a power density of 8.9 W/m2 (0.8 W/ft2) compared to a typical hospital density of 15.3 W/m2 (1.4 W/ft2). The next step was to develop an efficient and cost-effective HVAC system that would reduce the hospital’s operating energy and, at the same time, be compliant with all applicable hospital codes and standards, and meet the LEED requirements for indoor air quality and thermal comfort.
Due to the 30-year operating components of the P3 contract and operating cost guarantees, all energy-saving strategies had to be proven technologies with long-term reliability and repeatability. The use of aquifer water for heat pump heating and cooling, for example, was deemed to be too risky even though it has a fast payback and would have easily achieved the three LEED energy points.
Citation: ASHRAE Journal, vol. 54, no. 6, June 2012 ©2012
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