Controlling humidity at Gold Coast University Hospital
Air Change shares how Gold Coast University Hospital’s HVAC system was designed to cater for the high humidity of the hospital’s subtropical location.
Detailed planning and the design stage process for the Gold Coast University Hospital (GCUH) started in 2005, with construction taking place later in 2008. In 2009, members of the Engineering Joint Venture (EJV) Mechanical Services Design team for GCUH started to source options for the hospital’s HVAC requirements.
Hospitals and health facilities have specific HVAC requirements due to the nature of the facility, and a system that could precondition a high volume of outside air was required for a large portion of the project.
HVAC REQUIREMENTS SPECIFIC TO HOSPITALS
In HVAC Design for Healthcare Facilities, A Bhatia from the Continuing Education and Development Engineering Inc notes that these include:
- the need to restrict air movement in and between the various departments (no cross-air movement)
- specific requirements for ventilation and filtration to dilute and reduce contamination in the form of odour, airborne microorganisms and viruses, and hazardous chemical and radioactive substances – ventilation effectiveness is very important to maintain appropriate indoor air quality
- different temperature and humidity requirements for various areas and the accurate control of environmental conditions, and
- design sophistication to minimise the risk of the transmission of airborne pathogens and to preserve a sterile and healing environment for patients and staff.
According to Bhatia, these requirements demand high quantities of outside air, along with significant treatment of this ventilation air, including cooling, dehumidifying, reheating, humidifying and filtration.
CONTROLLING HUMIDITY AT GCUH
The subtropical location of GCUH, which is near the coast of southeast Queensland, meant that humidity control for the high volume of supplied outside air was of critical importance.
To overcome this issue of high humidity, chilled water dehumidification units were selected. These units accurately control both temperature and humidity through inbuilt sensible plate heat exchangers, which provide the pre-cool, dehumidification and reheating of the incoming outside air. These functions are controlled via an integrated proprietary control system that integrates with the site’s building control management system.
A total of 13 chilled water dehumidification units and 13 energy recovery ventilators, ranging from 4000 to 7000 litres per second, were installed at the end of 2011. The dehumidification units also assist with building pressurisation and assist in preventing the ingress of moisture into the building.
ADDRESSING THE HIGH LATENT LOAD
The GCUH design team initially looked to the Green Building Council of Australia’s (GBCA’s) Health Facilities Design Tool to establish sustainable design principles. As the design tool does not make allowances for the subtropical climate in which the GCUH exists, however, achieving a high energy efficiency score was difficult. The high latent load created by the climatic conditions needed to be addressed directly to improve the facility’s overall energy efficiency.
The dehumidification units allow the HVAC system to efficiently control this latent load. The main source of energy efficiency attributed to the dehumidification units is that they provide pre-cool and reheating via the air-to-air counter flow plate heat exchanger only using fan energy; therefore, reducing the amount of energy consumed to condition the high air volume. EJV found that the cost of achieving a GBCA four-star Green Star was reduced by a factor of four and it became within reach of the budget.
GOLD COAST UNIVERSITY HOSPITAL: THE STATS
The Gold Coast University Hospital (GCUH) was the largest single hospital infrastructure project in construction within Australia at the time of writing. The project is being undertaken by Queensland Health and is worth $1.76 billion, according to Aurecon.
Lend Lease notes that, once completed, the latest expansion to Queensland’s health services will cover an area over 170,000 square metres and be over nine storeys high, with 2300 on-site workers having completed over eight million man hours of work. This addition to the Queensland health institution is set to replace the existing Gold Coast Hospital, which was built in the 1970s, and will include 750 new beds with specialist cardiac services, neonatal intensive care, neuroscience, cancer radiotherapy, seven new operating theatres and a trauma response area, including a helicopter retrieval service and rooftop helipad.
GCUH is located adjacent to Griffith University South Campus, and will also serve as a teaching and learning facility. The Gold Coast Campus already boasts state-of-the-art health facilities, including the $36 million Griffith Centre for Medicine and Oral Health. Environmentally sustainable products were integrated throughout the project to minimise its impact. These included energy efficient lighting, sustainable waste management and the use of recycled materials. Queensland Health’s GCUH is set for completion in December 2012.