Cool House at the National Orchid Garden, Singapore

Cool House at the National Orchid Garden
Cool House at the National Orchid Garden

The National Orchid Garden (NOG) in the UNESCO World Heritage Singapore Botanic Gardens displays the largest collection of orchids in the world. The NOG creates an ideal environment for plants from a wide variety of climatic zones, ranging from lowlands to high-altitude tropical mountain forests.

The Sembcorp Cool House was remodelled and integrated into the Tropical Montane Orchidetum. Much of the original cool house was preserved, but now the seamless expansion created a much larger space that is tall enough to provide visitors with both terrestrial and arboreal zones of the montane forest. It is emulated to a high mountain forest of 1,000 to 2,000 meters, with appropriate climatic conditions and ambient temperatures ranging from 60 to 73° F (16 to 23 °C). Thus, it displays a variety of orchids and other plants from the mountain forest - in a glass house on the equator! Each of the Orchidetum exhibit buildings has been expanded beyond its original size, nearly tripling the total exhibit space.

Transsolar advised on the facade, climate and energy concept. The challenge was to integrate the complex aspects of light and ideal growing conditions for plants in terms of air temperatures and humidity, with complex requirements for visitor’s comfort, while keeping the energy demand as low as possible.

The project began with a site visit, during which various measurements were taken. The measurements served as the basis for the project simulations and design decisions. The data from the measurements was used to create and calibrate a digital twin of the existing building. All passive elements or strategies proposed by Transsolar were measured and their effectiveness verified.

The lighting distribution within the Sembcorp Cool House was extensively simulated, calculated and evaluated in three dimensions. In addition to the glazing, the shading played a decisive role. In terms of comfort, these principles apply: high radiant temperatures require low air temperatures. Greenery significantly reduces radiant temperatures. With planting, air temperatures do not need to be as low to provide the same comfort.
The primary consideration was not the shadows from the park's surroundings of to architecture and trees during the course of the day, but because of the steeply shining sun, the shading from the vegetation in the glass house itself. Therefore, it was necessary to model plantings in three dimensions and define lighting conditions from the roof of leaves to terrestrial locations through simulations.

A considerable part of the cooling load is provided by misting and evapotranspiration from the plants. This was also taken into account in the complex thermal-hygric simulations.