It is important the Hawaiian primary architecture to be used in defining the developing and future architecture of these islands. Improving the energy efficiency of Hawaii’s buildings, both old and new, offers tremendous potential to save energy especially for the cooling needs. Therefor it is of major importance to follow the roles for the energetic design that the “Watson and Labs matrix” provides.
The combination of tropical sun and western architecture influences can dramatically affect new constructions regarding the heating load and can result in the requirement of an air conditioning system. However, thanks to the bioclimatic design, the reasonable analysis of all the parameters can influence the final energetic balance and lead to a more sufficient result.
Firstly, the orientation and configuration of a building are critically important due to their strong influence on the design of effective solar control and daylight systems, as well as their impact on the performance of naturally ventilated buildings. Building orientation determines the amount of solar radiation falling on the wall and roof of the building and the ventilative effectiveness of the building’s openings. Building shape also determines the depth to which daylight can penetrate and the effectiveness of cross ventilation.
Reduce Solar gains
In the case of Hawaii, it is desirable to minimize the wall area and especially glass area facing east and west. These orientations receive long periods of exposure to the hot summer sun and are difficult to shade effectively. However, the key effective shading is to intercept the heat outside the building. Overhangs and eaves are effective against the midday sun, particularly on the south side. For the lower morning and afternoon sun, vertical fins are desirable on the east and west façade.
Ventilation and air changes
The optimum orientation for ventilation depends on the window location as well as the direction of the prevailing winds. When windows are in opposite walls, rotating the building 45 degrees with respect of the prevailing wind direction provides the highest average velocities and the best overall distribution of the air movement within the space. Inlets for natural ventilation can often be designed for less optimal wind orientations, because the reduction of solar gains is more important. Lat but not least, it is desirable to have a compact plan to minimize the surface area exposed to the sun and exterior openings should be well sealed to minimize the loss of cooled air.
Heat transfer
In our tropical climate, the major source of heat gains is radiant heat through windows, roofs and walls. Therefore the selection of the building systems and the materials will dramatically affect the building's energy performance. To reduce the amount of heat that penetrates a building’s exterior envelope, the materials selected should be capable of reducing both conductive and radiant heat flow. For example, from an energetic performance standpoint, glazing materials should have a high daylight transmission and a low shading coefficient. As far as the walls and roof is concerned, when they are heavily exposed to solar radiation an effective and appropriate level of insulation should be determined. Stopping the flow of heat into a building through radiation may be more important in Hawaii, particularly in roofs, since they are the most exposed to the sun areas. Most forms of thermal insulation restrict conductive and convective heat flow by trapping layers of still air.
To sum up, a number of common features have been found in the different tropical regions. These features are independent of location, social organisation or religious affiliation. Though each tropical region is unique, they are all inextricably linked through shared patterns of climatic adaptations and by surprisingly specific but similar cultural forms and colonial influences that have evolved and diffused to meet their shared requirements. Building construction is determined by the distribution of naturally available building materials, one exemplar being palm thatch which is available and readily used in most tropical regions. The table listed below provides a summary of building evolution in four different tropical regions, highlighting the common features of traditional building and their modern adaptions. These modern adaptations provide the recommended design methods and materials for tropical regions.