According to ENERGY STAR, the hospital facilities provide acute care services intended to treat patients for short periods of time, including emergency medical care, physician's office services, diagnostic care, ambulatory care, surgical care, and limited specialty services such as rehabilitation and cancer care. Since there are a wide variety of treatments hospitals can provide, their energy use intensity and baseline assumptions can vary. Some of the key differences arise from a change in ventilation rate and equipment load. This article highlights the impact on the hospital energy use for different types of hospitals.
The hospital building referred in this article is a prototype model generated by Pacific Northwest National Laboratory (PNNL) and located in Denver, Colorado. The energy code selected is ASHRAE 90.1 2016 version. Following table contains key inputs for this analysis:
// Energy Usage Intensity with default CFM rate (10 CFM/person)
Cove.tool automates the total CFM value based on 10 CFM/person rate for Hospital. The CFM rate varies from zone to zone in a hospital (e.g. patient room, physical therapy, operating room, etc.) which makes the total CFM estimation tricky as the floor plate distribution for different zones vary based on design.
The factors taken into account for automated CFM calculation are occupant density (ft2/person), total floor area (ft2), and the ventilation rate (CFM/person).
The automated inputs EUI breakdown is indicated in following images:
// Design Variation 1: Patient Rooms 70% and Physical Therapy 30% of the floor-plate
Table E-1 from ASHRAE 62.1 2007 version lists down the CFM/person rate for various healthcare facility zones. For calculating the total CFM of a hospital whose 70% floor-plate (168,987 ft2) is patient rooms and 30% floor-plate (72423 ft2) is physical therapy, let's keep the occupant density constant at 200 ft2/person.
The outdoor air rate for patient room is 25 cfm/person and for physical therapy is 15 cfm/person according to the Table E-1 from ASHRAE 62.1 2007. Therefore, the total CFM for this hospital design would be 26555.09.
After hitting the 'recalculate' button, total EUI went up by 2.27 kBtu/ft2. The graphs below indicate the updated EUI breakdown.
// Design Variation 2: Operating Rooms 40%, Patient Rooms 40% and Recovery and ICU 20% of the floor-plate
For calculating the total CFM of a hospital whose 40% floor-plate (96,564 ft2) is operating rooms, 40% floor-plate (96,564 ft2) is patient rooms and 20% floor-plate (48,242 ft2) is recovery and ICU, let's keep the occupant density constant at 200 ft2/person.
The outdoor air rate for operating room is 30 cfm/person, for patient room is 25 cfm/person, and for recovery and ICU is 15 cfm/person according to the Table E-1 from ASHRAE 62.1 2007. Therefore, the total CFM for this hospital design would be 30176.25.
After hitting the 'recalculate' button, total EUI went up by 2.95 kBtu/ft2. The graphs below indicate the updated EUI breakdown.
// Modifying the Appliance Load (Design 2 as an example)
The automated appliance load of 1 W/ft2 for hospital building type is taken from ASHRAE User's manual Table G-C. There are many designs where this load can be significantly higher based on the design. For example, it is not unrealistic to consider that the design 2, which consists of operating rooms, patient rooms and recovery & ICU, will have a heavy appliance load such as 3 W/ft2.
The modified EUI breakdown is shown in the graphs below:
Additionally, the key inputs like the heating system COP, Cooling system COP, Occupancy schedule, and Occupant density can be customized to reflect the project conditions more accurately. The customized values can be converted into template so that it can be used by different users within the firm. This can be achieved by checking the 'convert to template' box below the energy code dropdown.