Sustainable Siting and Passive Solar Design

Global Targets and the Definition of Net Zero Energy Buildings

• Path to Net Zero: Key Milestones (IEA Reports):     * By $2030$: The goal is for all new buildings to be zero-carbon ready.     * By $2035$: Most appliances and cooling systems sold globally must be classified as "best in class."     * By $2040$: Target for $50\%$ of existing buildings to be retrofitted to zero-carbon ready levels.     * By $2045$: Target for $50\%$ of heating demand to be met by heat pumps.     * By $2050$: Target for $85\%$ of existing buildings to be retrofitted to zero-carbon ready levels.

• Zero Energy Building (ZEB) / Net Zero Energy (NZE) Definition:     * A building characterized by net zero energy consumption on an annual basis.     * The total amount of energy used by the building is equal to the amount of renewable energy created on-site.     * Alternative definitions include the use of off-site renewable energy sources.     * Underlying technologies to achieve this include heat pumps, high-efficiency windows, advanced insulation, and solar panels.

The Net Zero Energy Building (NZEB) Pyramid

• The development of an NZEB is conceptualized as a pyramid with hierarchical tiers, starting from foundational passive design to active renewable production:     * Foundation: Passive solar design.     * Tier 2: High-performance envelope (insulation and airtightness).     * Tier 3: Behavior (occupant usage and active practices).     * Tier 4: High-efficiency technology (EnergyStar, HVAC, heat pumps).     * Apex: Renewable Energy (Solar panels, wind turbines, geothermal).

Fundamentals of Passive Solar Building Design

• Core Principle: Passive solar design utilizes windows, walls, and floors to collect, store, reflect, and distribute solar energy as heat during the winter, while rejecting solar heat during the summer.

• Mechanical Involvement: This process does not involve the use of mechanical or electrical devices.

• Vernacular Techniques: Modern sustainable design draws inspiration from traditional, regional vernacular architecture techniques that adapted to local climates before the advent of modern HVAC.

• Key Design Elements:     * Site analysis to leverage local climate.     * Window placement, size, and glazing type selection.     * Thermal insulation and thermal mass.     * Shading strategies.

• Certification Body: The Passivhaus Institut (Certified Passivhaus) provides rigorous standards for these designs.

Climatic Site Conditions and Orientation

• Site Condition Factors: Consideration must be given to sun path, wind patterns, drainage, natural vegetation, and landscape features.

• Sun Path Optimization: Buildings should maximize passive solar gain in the winter and minimize it in the summer.

• Wind Patterns: The dwelling should be oriented to take maximum advantage of prevailing winds for natural cooling.

• Drainage and Runoff: Natural site drainage can be enhanced to utilize rainwater and runoff for outdoor irrigation purposes.

• Topographical Placement Based on Climate:     * Cold Climates: Houses are often placed midway along a slope to be protected from ridge winds and the collection of cold air in valleys.     * Hot and Arid Climates: Valleys can be utilized as they draw cool air at night.     * Hot and Humid Climates: Ridges are preferred as they are subject to year-round breezes and lower humidity levels.

• Shadow Management: A dwelling must remain clear of shadows from surrounding buildings. Minimum distance between structures is determined by:     * Height of the adjacent building.     * Grade of the land.     * Sun’s specific angle.

• Detailed Orientation Logic:     * Dwellings should receive the most direct sunlight throughout the day.     * The elongated side of the building should face south in the Northern Hemisphere.     * True South vs. Magnetic South: Orientation must be toward true (solar) south, which can differ from magnetic south by up to $20$ degrees.

Structural Shape and Internal Spatial Organization

• Building Shape and Efficiency:     * Larger surface areas correlate with greater heat loss.     * In general, a cube shape is more energy-efficient than an elongated rectangle due to a lower surface-area-to-volume ratio.     * Exception: In warm or humid climates, a stretched configuration is often preferred to facilitate cross-ventilation through openings at either end.

• Facade Strategy (Northern Hemisphere):     * North Facade: Receives little to no sunlight; openings should be minimized to prevent heat loss. In cold climates, doors and windows should comprise only $5\%$ to $10\%$ of the north facade. In warm climates, north-facing walls might provide natural light without significant heat gain.     * South Facade: Should feature large openings to allow sunlight entry. Heat acquired via passive gain on the south facade usually far exceeds the heat lost through the windows.

• Internal Zoning / Insulating Buffers:     * North Side (Buffer): Infrequently used areas like bedrooms, utility rooms, garages, or hallways should be placed here.     * South Side (Living): Essential living areas like dining rooms, kitchens, and living rooms should face south to maximize sunlight exposure where occupants spend the most time.

Shading and Thermal Control Strategies

• Seasonal Shading: Solar rays must be limited in summer to prevent overheating.

• Roof Overhangs: The width of the overhang is adjusted based on the altitude of the sun; it shades the dwelling from high-angle summer rays while allowing low-angle winter sunlight to penetrate.

• Light Shelves:     * Installed at approximately the two-thirds point of the window height.     * Shades the lower glazing portion while reflecting light into the ceiling space.     * Reflected light provides illumination without the intense heat gain associated with direct sunlight.

• Vegetation as Control:     * Deciduous Trees: Planted on the south side; they provide full foliage/shade in summer and lose leaves in winter to allow solar gain.     * Trees can also act as wind management barriers.

• Thermal Mass: Surface materials that absorb and store heat during the day for later distribution.

High-Performance Building Envelope and Technology

• Envelope Goals: Focus on higher insulation, airtightness, and the reduction of thermal bridging.

• R-Value Insulation Benchmarks (Strategy $5/10/20/40/80$):     * Windows: $R-5$     * Below Slab: $R-10$     * Walls Below Grade: $R-20$     * Walls Above Grade: $R-40$     * Roof: $R-80$

• Behavioral Adjustments: Includes active "vernacular" practices, smart thermostats, de-centralized temperature control, and general consumption reduction.

• High-Efficiency Technology: EnergyStar appliances, high-performance HVAC systems, and heat pumps.

• Renewable Energy Sources: Solar panels, wind turbines, and geothermal heat pumps.

Case Study 1: Texas Passive House (2021 Deep Freeze)

• Scenario: A Passive House owned by Trey Farmer during a record $144$-hour period of below-freezing temperatures in Texas.

• Building Specs: The house has solar panels and is intended to be "a little more than net zero," though it lacked battery backup, leading to power loss when the grid failed.

• Temperature Performance:     * The thermostat was set at $68^{\circ}F$; when the power failed at $1:00\,am$, it was $9^{\circ}F$ outside and $62^{\circ}F$ inside.     * The second night, the interior dropped to $53^{\circ}F$.     * The coldest recorded internal temperature was $49^{\circ}F$ on the third day.

• Comparisons:     * House 1 ($800\,sq\,ft$, built $1919$): Single-pane windows, no wall insulation ($R-80$ attic, $R-20$ floor). It dropped below $40^{\circ}F$ in just $5$ hours, hovering at $31^{\circ}F$.     * House 2 ($2,300\,sq\,ft$, built $2009$): Code-built, spray foam insulation. Dropped below $40^{\circ}F$ in $48$ hours.     * Rocky Mountain Institute Study ($2020$): Passive House envelopes can maintain safe indoor temperatures for over $6$ days before falling below $40^{\circ}F$.

Case Study 2: Florida Passive Cooling (Miami Beach and Beyond)

• Prairie House (Miami Beach):     * Cost: $\$15.2$ million luxury home; size: $3,200\,sq\,ft$. Architect: René Gonzalez.     * Design: "Porous" structure with courtyards and breezeways.     * Elevation: Building is elevated $14\,feet$ to avoid floods and allow cool air circulation under the floor.     * Impact: A single courtyard can lower energy bills by approximately $7\%$ on average (University of Cadiz and Seville study, $2021$).     * Roof: Covered in plants to shade the roof and cool the interior.

• Stillman House (Coconut Grove): Designed by Rufus Nims; uses louvered shutters to circulate air while providing shade.

• The Crossings (South Florida):     * Features $37$ windows and ceilings designed to capture rising hot air and vent it through high second-floor windows.     * Orientation: Angled to face prevailing southeasterly breezes.     * Vegetation: $50$ trees planted on a quarter-acre lot to shade the south-facing wall and the A/C condenser.

Building Codes and Evolution of Efficiency

• Implementation Methods:     1. Building Codes ("The Stick"): Mandatory legal standards.     2. Building Rating Systems ("The Carrot"): Incentive-based certifications.

• Evolution of Model Energy Codes (1983 vs. 2012):     * 1983 House (MEC):         * Wall Insulation: $R-13$         * Ceiling Insulation: $R-19$         * Floor Insulation: $R-6$         * Window $U$-value: $1.1$         * Air Leakage Testing: Not required.     * 2012 House (IECC):         * Wall Insulation: $R-20$         * Ceiling Insulation: $R-38$         * Floor Insulation: $R-19$         * Window $U$-value: $0.35$; Solar Heat Gain Coefficient (SHGC): $0.25$         * Air Leakage Testing: Mandatory.         * Lighting: $75\%$ high-efficiency lamps.     * Efficiency Gains: Stronger codes make homes up to $44\%$ more efficient, potentially saving nearly $\$400$ annually (in $2012$ dollars).

Building Certification Systems

• BREEAM: One of the oldest green rating systems; basis for many others. Star rating from $1$ to $6$. Certifies new construction, in-use buildings, and refurbishments.

• LEED (Leadership in Energy and Environmental Design):     * Certifies $2.2$ million square feet daily across $165$ countries.     * Levels: Certified ($40-49\%$), Silver ($50-59\%$), Gold ($60-79\%$), Platinum ($80\%+$).     * Credit Categories: Integrative Process, Location and Transportation, Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, Indoor Environmental Quality, Regional Priority, and Innovation.

• Green Globes: Offered via the Green Building Initiative; evaluates environmental sustainability, health, and resilience.

• WELL: Focuses exclusively on occupant health and well-being; requires an Energy Star score of $75\%+$ and annual reporting.

• Florida Green Building Coalition (FGBC):     * Over $29,000$ projects certified since $2000$.     * Criteria specific to Florida: hot-humid environment, topography, geology, and natural disasters.     * Includes standards for Single-Family Homes, Local Governments, Land Developments, Commercial Buildings, and Hi-Rises.

• Additional Certifications: NABERS, International Living Future Institute, NGBS Green, Greenguard, and CASBEE.

Sustainable Buildings at the University of Florida (UF)

• UF holds more sustainable building certifications than any other public higher education institution.

• Approximately $20\%$ of UF's total building inventory is sustainably certified.

• Rinker Hall: The first LEED Gold certified building in the state of Florida ($2004$).

• Larsen Hall: LEED Certified (Commercial Interior).

Group Project 2 Requirements

• Objective: Analyze the sustainability of a specific building on the UF campus.

• Tasks:     * Select a building (over $900$ available, first come, first served).     * Create a rating system with at least $5$ criteria (covering environmental, social, and economic factors).     * Assess if the building is sustainable based on the created criteria.     * Research existing ratings (LEED, WELL, Green Globes) and their scores.     * Propose $2-3$ specific improvements for sustainability.