Passengers on cruise ships like to wander in and out much as they would on dry land, i.e. without having to negotiate doors that open and shut as they pass. But creating such indoor/outdoor spaces onboard ships is demanding given the particular requirements of heating, ventilation and air conditioning (HVAC).
Humidity is a major source of those challenges e.g. creating cabins that feature doors which can be opened and thus re move an entire wall to the balcony, says Uwe Jakubowsky, engineering manager at Aerius, the German HVAC specialist.
If the temperature inside the cabin is kept low and the air outside hot and humid, as is often the case when the ship operates in warm climates, condensation starts to build within the space. Over pressurising the cabin offers a way to tackle the problem, he tells The Naval Architect.
Aerius supplies HVAC systems to the Edge class ships of Celebrity Cruises, which are being built at Chantiers del'Atlantique in France. These vessels feature Infinite Veranda cabins, in which the wall to the balcony slides to the sides and transforms one side of the cabin into outdoor space.
On the other hand, a glass panel can be raised to turn the balcony into inside space,with a floor to ceiling window facing the sea. Similar cabins are found on other recent newbuildings, such as P & O Cruises’ Iona, where they are called Conservatory Mini Suites.
Buffet areas are another location where such an arrangement would be quite welcome.In most cases, the main pool area lies in front of the restaurant and an open deck aft of it. People want to sit outside, so there is a heavy flow in and out. Automatic sliding doors are used to separate the indoor area from outdoor ones, and making these indoor/outdoor areas seamless poses its own challenges.
“In lido buffet zones, you need to use air locks, over pressurising the inside areas does not work,” Jakubowsky says. The ship’s forward motion creates a wind and if doors are open to a deck aft of the buffet, the airflow through the space becomes so strong that it cannot be sealed off with just over pressurising the area, he explains.
Humidity and safety
Joep Hopman, CEO of the Dutch HVAC system supplier Heinen & Hopman, comments that air can only be blown in by the HVAC system in indoor/ outdoor areas, other wise humidity and condensation becomes a problem. This leads to a loss of system efficiency in these areas, which he says amounts to the region of 25-30%.
Two questions have hampered efforts to better merge indoor and outdoor areas onboard cruiseships, says Vesa Marttinen, senior advisor at the Finnish consulting company Marine Cycles. “The first one is fire safety: what category spaces are we talking about in SOLAS terms. The second one relates to air conditioning. Removing humidity from the air in areas inside has been a problem,” he tells The Naval Architect.
Cruise ships operate in various climate conditions, with significant fluctuations in outside air temperature, yet the experience for passengers should always remain a pleasant one.‘Air curtains’ produced by the air conditioning system onboard have been developed to tackle these problems as well as indoor humidity issues, and the results have improved over the years.
However, when considering this method, operating costs from increased use of air conditioning capacity and capital expenditure linked to the increased capacity required from the air conditioning plant enter the picture as well.
“In recent times, there has been a lot of effort in the development of HVAC to allow air circulation without cooling it. Ultimately, the question is about whether passengers are able and willing to pay for any new experience onboard,” Marttinen says.
In the cruise industry, innovations onboard ships are often based on consumer trends that are taking place ashore. As the demand for a new innovation concept grows, cruise lines will need to introduce ones onboard, he concludes.
Esko Nousiainen, who heads the cruise business area at the Finnish HVAC specialist Koja, comments that commercial reasons drive the industry to introduce new features, including cabins that can be converted into indoor/outdoor areas. “There are quite a few new ships on order and many of them are due to enter service in the near future. There is a need for special features to make vessels stand out,” he adds.
However, given the fact that features such as these types of cabins involve both higher operating expenses as a result of increased energy consumption of the HVAC system and a rise in capital expenditure as well, they will be introduced in limited numbers and at higher end cabin categories.
