9.3 Sustainable & Green Design Principles

Sustainable & Green Design Principles

Passive Design First, Mechanical Systems Second

The ALE tests a specific hierarchy of decision-making that any sustainable design must follow: passive design strategies always come before mechanical systems, not alongside them as an afterthought. A design that first uses orientation, shading, and natural ventilation to cut heat gain, and daylighting to cut electric lighting demand, needs a smaller, cheaper, more efficient air-conditioning and lighting system than a design that ignores passive strategies and tries to compensate purely with equipment. This sequencing - passive first, active second - is the single idea sustainable-design exam items return to most often.

Daylighting uses window placement, orientation favoring the more easily shaded north- and south-facing facades discussed in the previous section, light shelves, clerestories, and skylights to bring usable daylight deep into a floor plate, reducing dependence on artificial lighting during daytime hours. Natural ventilation - cross-ventilation and the stack effect, both covered in the previous section - reduces or eliminates the need for mechanical cooling in appropriately sized and oriented spaces. Only after these passive measures are exhausted should a design turn to efficient mechanical systems, such as right-sized HVAC equipment, LED lighting, and occupancy or daylight sensors, to cover the residual load.

Water Conservation and Rainwater Harvesting

Water strategies matter in a country that receives heavy, concentrated monsoon rainfall during the Habagat season yet also experiences dry-season water stress in many urban areas. Key strategies tested on the ALE include:

• Rainwater harvesting: capturing roof runoff in cisterns or storage tanks for irrigation, toilet flushing, or washing, reducing demand on the municipal water supply and reducing stormwater runoff that would otherwise overload city drainage during heavy rains.
• Greywater reuse: reusing lightly used water, such as from lavatories, for non-potable purposes like landscape irrigation.
• Low-flow fixtures: reducing potable water demand at the point of use.
• Permeable paving and on-site retention: allowing stormwater to infiltrate and recharge groundwater rather than sheeting off-site, which both conserves water and reduces flood risk to the site and its neighbors, connecting directly back to the drainage findings from site analysis.

Energy-Efficient Materials and Systems

Once passive design has minimized the base load, material and system choices further cut energy consumption:

• High-performance or tinted, low-emissivity glazing reduces solar heat gain through windows without sacrificing daylight.
• Roof insulation and high-reflectance cool roofing slow heat transfer through the building's most sun-exposed surface, critical in a climate where the roof, not the walls, usually carries the largest solar load.
• Efficient lighting and HVAC equipment, such as LED fixtures and higher-efficiency, variable-speed air-conditioning units, cut the electrical load that remains after passive measures.
• Locally sourced and renewable materials, such as bamboo, engineered wood, and indigenous stone, reduce the embodied energy spent on transport and manufacturing compared with imported alternatives.
• On-site renewable energy, particularly rooftop solar photovoltaic (PV) systems, is increasingly specified given the country's abundant year-round solar resource.

Philippine Green Building Context

The Philippine Green Building Council (PHILGBC), incorporated in 2007, is the Philippines' recognized voice for green building practice and a member of the World Green Building Council's Asia-Pacific network. In 2009, PHILGBC established BERDE (Building for Ecologically Responsive Design Excellence) - the country's own, government-recognized National Voluntary Green Building Rating System, recognized by the Department of Energy. BERDE evaluates a project across multiple impact categories, including management, sites and community, energy, water, materials and circularity, and health and well-being, and awards a star rating from 1 to 5 stars based on the percentage of achievable points a project earns, with higher star levels representing progressively more exemplary environmental performance above the mandatory code baseline.

Separately, in 2015 the Department of Public Works and Highways (DPWH) adopted the Philippine Green Building Code as a referral code of the National Building Code (PD 1096), placing green building requirements alongside other referral codes such as the Fire Code and BP 344, the Accessibility Law, in the same regulatory family. Some local government units have gone further with mandatory local ordinances: Quezon City's green building ordinance, first adopted in 2009 and updated since, requires qualifying new buildings to comply with green site, energy, water, and material provisions, backed by tax-credit incentives for developers who exceed the minimum.

For ALE purposes, the exam distinguishes between the mandatory baseline set by PD 1096, the Philippine Green Building Code referral code, and applicable local ordinances, and voluntary certification through BERDE, which recognizes performance beyond that baseline. A design candidate should be able to identify which sustainable strategies are simply good, code-compliant tropical design practice - orientation, shading, natural ventilation - versus which represent additional, certifiable green performance, such as measured water and energy reduction targets, materials sourcing, and renewable energy generation, under a rating system like BERDE.

Quick Reference: Passive-First Sustainable Design Checklist

This passive-first sequence is the framework the ALE expects a candidate to apply to any sustainable-design prompt in the design problem.