Suvarnabhumi International Airport Bangkok - Innovative Climate Concept
The terminal’s envelope
Climate engineers examine a building in its entirety, and combine physical laws with technology in order to achieve optimal human comfort at a minimum of energy consumption. Bangkok’s climate has temperatures from 25°C–30°C, a high level of relative humidity and solar radiation, and solar altitudes near the zenith. An international airport requiring a constant air temperature (24°C) and 50–60% relative humidity, calls for continual cooling and dehumidification. This places high demands on the building envelope to minimise the effects of solar loads. The sheds in the terminal utilize fritted glass (95% opacity) on the north side, and solid panels limiting the solar gain to 1% of the radiation striking the south side. A cantilevered, louvered roof shades the 40-metre-high vertical glazing.
Floor cooling and displacement ventilation
Conventional air-conditioning of large-volume enclosures with internal building elements requires an inordinate amount of energy. By partitioning the building in zones of unconditioned spaces and cooled occupied zones, the total cooling demand is drastically reduced because it is only applied where needed. Two cooling systems are used. First, radiant floor cooling directly removes radiation striking the floor. The second system is an air displacement system, with controllable air stream supplying cool air to the space at floor level and at low velocity. In addition to using a portion of return air for the rejection of convection heat loads, the system provides the required cooled and dehumidified fresh air to the space.
Thermal air stratification
Because cool air is heavier than warm air, thermal stratification occurs in the building, supported by the radiant floor cooling (ill. 1). The air-conditioned zone extends only 2.50 m above floor level. In the higher levels the air is near ambient temperature; therefore, it is not necessary to insulate this part of the envelope. Due to thermal air stratification, this has no influence on the conditioned, inhabited spaces below.
Innovative three-ply membrane roof
In the concourses the same cooling principle was applied, but the circumstances are different. Transparent glazing and translucent panels alternate in the building envelope. The membrane roof had to fulfil a number of requirements. It must admit 1–2% of the sunlight, as diffuse light, in order to provide the basic ambient lighting (ill. 2); it does not, however, permit additional solar radiation to enter, in order to limit the energy gain in the space in use (ill. 3). In addition, the heat radiation from the roof must be reduced to approximately 40% in order to meet the energy consumption limitations. The newly developed membrane package consists of an outer membrane of Teflon-coated glass fibre, a coated inner membrane level, and transparent PC sheets on a steel-cable mesh. The inner, translucent membrane serves, in conjunction with the PC sheets, as a baffle. The coating on the side facing the interior has low emissivity characteristics. Low-e coatings block the radiative heat exchange between the warm membrane and the inhabited spaces. An additional advantage: instead of the roof’s heat radiation being reflected into the space, the cooled floor surfaces’ radiation is reflected by a thermal mirror, improving the occupants’ comfort.