Projects

It is not often that a retrofit is commissioned with the primary objective of improving occupant comfort. The retrofit of the Asian Development Bank (ADB) Headquarters in Manila, which commenced design in 2003 and was completed in 2006, is unique for two reasons. First, it was an enlightened initiative by the building's owner in direct response to perceived occupant discomfort. In some of the building's offices, this discomfort was due to little or no access to natural light. Second, the daylight enhancement system that was built remains one of the largest mirror reflectors ever installed in a building in Asia.

The ADB building was built and commissioned in the late 1980s; it is a sizeable office building with a deep floor plate in which some personnel have offices adjacent to the building's two atria. These atria—30 by 30 metres in plan, 9-storeys high—are capped with a pyramidal roof with a central skylight and continuous clerestory windows along the perimeter. Dense grillage beneath all openings limit direct entry of sunlight; the shading system is so effective that on a sunny day in Manila, the level of natural light at the base of the atria—used as a library and staff lounge—was measured at less than 100 lux, not enough to read a newspaper without the aid of electrical lights. The atria were effectively dark, gloomy spaces, disconnected from any sense of the outdoors.

Consultants from CPGreen (Singapore) were asked to propose a cost-effective method of increasing daylight levels. Initial ideas included a new fully glazed roof—which brought in abundant light, and also much heat—and new skylights cut into the existing roof structure. For a variety of reasons—such as minimisation of downtime and risk of typhoons during construction—it was decided that the solution should not require any replacement or puncturing of the existing building envelope. The consultants proposed a system of mirror reflectors—installed around the clerestory windows—to effectively catch and redirect daylight into the atria.

In addition to the new mirrors, existing grillage along clerestory openings was modified to have bigger openings; grillage in the central skylight was removed altogether. External roof eaves were cut and the internal roof soffit was repainted white, to improve internal reflectance.

Following the retrofit, onsite measurements showed a six-fold increase in daylight levels under sunny conditions, and a four-fold increase in daylight levels under overcast conditions, numbers that were consistent with simulations carried at the drawing board. At the atrium floor, light levels of 300 lux or more were attained 75 percent of the time during opening hours.

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