Sustainable Design Overview
Sustainable design integrates environmental performance into every phase of a project, from site selection through material specification. The ARE tests both conceptual understanding (passive strategies, climate response) and applied knowledge (certification systems, energy metrics), primarily in PA and PPD.
Passive Design Strategies
Passive strategies reduce reliance on mechanical systems by working with climate and site conditions:
- Passive solar heating: South-facing glazing (northern hemisphere) with thermal mass to absorb and slowly release heat.
- Natural ventilation: Cross-ventilation and stack effect to move air without mechanical assistance.
- Daylighting: Orientation, glazing placement, and shading to maximize usable daylight while controlling glare and heat gain.
- Thermal mass: Materials (concrete, masonry, water) that store and release heat to moderate temperature swings.
- Shading devices: Overhangs, louvers, and fins sized using sun angle calculations to block summer sun while admitting winter sun.
These strategies are foundational to Site Analysis and inform early massing and orientation decisions.
LEED Certification
LEED (Leadership in Energy and Environmental Design), administered by USGBC, awards points across categories including Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, and Indoor Environmental Quality. Certification levels - Certified, Silver, Gold, Platinum - are determined by total points earned.
Key Prerequisites and Credits
- Energy and Atmosphere: Requires minimum energy performance, often verified through energy modeling compared to an ASHRAE 90.1 baseline.
- Water Efficiency: Reduced potable water use through low-flow fixtures, and reduced outdoor water use through native/adapted planting.
- Materials and Resources: Life-cycle assessment, Environmental Product Declarations (EPDs), and construction waste management.
For a quick-reference summary of credit categories and thresholds, see the Sustainability Cheat Sheet.
Energy Modeling
Energy models simulate a building's annual energy use based on envelope performance, HVAC systems, lighting, and occupancy schedules. Common uses include code compliance (ASHRAE 90.1 performance path), LEED credit documentation, and comparing design alternatives. Models output metrics like Energy Use Intensity (EUI), measured in kBtu/sf/yr, useful for benchmarking against targets like AIA 2030 Challenge goals.
Material Selection
Sustainable material selection considers embodied carbon, recycled content, regional sourcing, durability, and indoor air quality (low-VOC finishes). Life-cycle assessment (LCA) evaluates environmental impact from extraction through disposal, complementing the life-cycle cost concepts in Cost Estimation.
Water Conservation
- Indoor: Low-flow fixtures, dual-flush toilets, and greywater reuse systems.
- Outdoor: Native/drought-tolerant landscaping, efficient irrigation, and rainwater harvesting.
- Stormwater: Bioswales, permeable paving, and green roofs manage runoff on site - see Environmental Systems.
Envelope Performance
The building envelope is central to energy performance; insulation, air barriers, and glazing selection are covered in depth in Building Envelope, and mechanical system efficiency in HVAC Systems.
Exam Tips
- Know which passive strategy addresses which climate challenge (e.g., thermal mass in hot-arid climates).
- Understand LEED category weighting conceptually rather than memorizing exact point values, which change between versions.
- Be able to explain how energy modeling supports design decisions, not just compliance documentation.
Sustainable design spans PPD and PA - sharpen your knowledge with free practice questions on AREprep.