Trans RINA, Vol 156, Part C1, Intl J Marine Design, Jan - Dec 2014 considered as an overall index of feasibility. More
importantly it establishes the relationship between lighting performance and occupancy where by a zone that Is frequently unoccupied during the day cannot take advantage of daylight harvesting and so has a limited impact on lighting energy consumption In comparison to lounge and dining areas. This reduction in the ability to utilise natural light reduces the strategies influence on the total energy performance of the zone. Combined with the low lighting level required to satisfy visual requirements its influence is outweighed by cooling load and heating loads.
In addition, the methodology adopted to this zone may not be entirely appropriate due to its focus on sensible loads which are mostly affected by the convective and radiative thermal exchanges which occur between the zone and the external façade which otherwise behaves as the primary thermal interface. However, as defined by such codes as the ISO 7546 [33] ventilation and humidity requirements apply and in many cases latent loads can far exceed sensible loads. As the thermal model defined within this
occupants exchanges other
methodology does not account for the between balconies which may
allow hot humid air into the cabin and other zones, it is likely that
design elements such as humidity
control, ventilation rates, thermal set points, glazing types and shading have a greater influence on overall energy performance. Nevertheless the simulation results indicate that a minimized glazing percentage is adequate in providing the required lighting level of 150 lux with large shading devices reducing the influence of solar gains. This is preferred from the perspective of energy consumption. These observations have been transferred into design considerations in the latter part of this paper.
3.3 THE IMPLICATION OF MOBILITY
The previous section introduces the connections between, form, fenestration, and operational behaviour of the zone and evolves the concept of an idealized window size through a parametric methodology. The method however is somewhat limited as the observations made cannot be directly translated into design alternatives as it does not account for the mobility of the vessel to a given itinerary. Each annual simulation is based on a static position with specific design parameters. To account for this variation many designs in multiple orientations locations and configurations
determine variations and
were considered and evaluated to commonalities across the
climatic variation of the Mediterranean. To do this an idealized window size is established for each orientation in each latitudinal zone, as per the methodology explained in the previous sections and then tested in 3 other locations spanning a wide latitudinal extent that encompasses
the Mediterranean basin in 4 different
orientations resulting in 12 different configurations per each idealized window size. This is illustrated in figure 14, 15 and 16 where by variations for each orientation
Figure 12 identifying the ideal glazing size for a north facing lounge/ day area in Barcelona
© 2014: The Royal Institution of Naval Architects C-105
and location is considered against the mean of the entire data set.
The largest variance from the mean annual energy
consumption of the 12 designs occurred in the cabin zone, day/lounge zone and dining zone resulting in a maximum difference from the mean of, 16.8%, 10.4% and 4.0% respectively. The cooling loads as indicated in figures 7, 10 and 11 present themselves as the most influential in terms of the global energy consumption of any design. These loads are mostly affected by shading devices and the glazing SHGC factor; therefore the maximum variance from the mean decreases to 14.7%, 4.19% and 1.2% respectively when a deep overhang of 2.5m is used – a similar result would be expected from glazing with low-e coatings or finishes which affected the transmittance of long wave radiation. A deeper analysis of this variance shows that the north facing façade commonly shows the best energy performance for any given location indicating that a southern western and eastern orientation is most detrimental to the overall energy consumption of a design. This suggest that a west-east or east to west itinerary in the southern most parts of the Mediterranean would benefit mostly from shading devices given that such an orientation would present 50% of the ships façade to the southerly sun. This synergy is also reflected in table 10 and 11, where by the northern orientation is typically granted a larger glazing percentage
in accordance to the ideal thus glazing
methodology discussed in previous sections. This bias towards a northern orientation is due to the reduction in dominant loads such as cooling,
allowing the
benefits of daylighting to have a greater influence in the global energy consumption of the design. Furthermore, by improving the insulative properties of the glazing to the same u-value as the external wall, we see that greater glazing percentages are possible due to the reduction in conductive gains and losses as illustrated in table 11 where by the glazing type has been adjusted such that the main optical properties
remain the same but the
insulative properties are brought to be comparable to the main external wall.
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