Architectural Science Building Science and Environmental Design Study Guide

Chapter 1: Energy Use and Energy Efficiency in Buildings

• The Significance of Building Energy Consumption

  • Buildings are the single largest consumer of energy globally, accounting for approximately $40\%$ of global final energy use.

  • The built environment generates around $33\%$ of global carbon dioxide ($CO_2$) emissions.

  • Global building stock is expected to double in floor area by 2060, with the majority of growth in the Global South and sub-Saharan Africa.

  • In Ghana, the building sector consumes approximately $50\%$ of total electricity, primarily for space cooling.

  • The mismatch between energy supply and demand in Ghana, driven by air conditioning demand in a hot climate, has led to persistent load-shedding known as 'dumsor'.

• Types of Building Energy Consumption

  • Operational Energy: Energy consumed during everyday use and occupation. It includes:

    • Heating, Ventilation and Air Conditioning (HVAC): In Ghana, mechanical cooling represents $45\text{--}60\%$ of a building's total operational energy.

    • Artificial lighting for occupied spaces, circulation, and emergency systems.

    • Domestic Hot Water (DHW) for washing and cooking.

    • Plug loads and appliances (computers, refrigerators).

    • Vertical transportation (lifts and escalators).

    • This typically represents $80\%$ to $90\%$ of total lifecycle energy for conventional buildings.

  • Embodied Energy: Energy consumed in production, including:

    • Raw material extraction (mining, logging).

    • Manufacturing (cement production, steel smelting).

    • Transportation and logistics.

    • Construction processes (equipment and temporary works).

    • End-of-life (demolition and waste processing).

• Factors Influencing Building Energy Consumption

  • Climate and Location:

    • Solar radiation intensity: Ghana receives average global horizontal irradiance of $4.5 \text{ to } 6.0\,kWh/m^2/day$.

    • Ambient temperature: Coast ranges from $24^\circ C \text{ to } 32^\circ C$, while the north can reach $40^\circ C$.

    • Relative humidity: High humidity in the south ($70\text{--}95\%$) renders evaporative cooling ineffective.

    • Wind patterns determine cross-ventilation potential.

    • Microclimate factors include urban canyon effects and proximity to water.

  • Building Characteristics:

    • Orientation: An east-west long axis minimises facade exposure to low-angle sun.

    • Envelope insulation: Thermal resistance of walls and roofs.

    • Window-to-Wall Ratio (WWR): High WWR increases cooling loads if not shaded.

    • Thermal mass: Materials like concrete or earth absorb heat by day and re-radiate it at night.

    • Air tightness: Uncontrolled infiltration adds to sensible and latent cooling loads.

  • Occupant Behaviour ('The Human Factor'):

    • Thermostat set points: Reducing the air conditioning set point by $1^\circ C$ (e.g., $24^\circ C$ to $23^\circ C$) can increase cooling energy by $6\text{--}8\%$.

    • Lighting and appliance management.

    • Window management relative to air conditioning use.

• Energy-Efficient Design Strategies

  • The hierarchy is: passive first, active second, renewable third.

  • Passive Design Strategies:

    • Building orientation: North and south facades allow for horizontal overhangs.

    • Natural ventilation: Cross-ventilation and stack ventilation (buoyancy-driven airflow).

    • Thermal mass: Effective in Ghana's hot-dry north due to high diurnal temperature swings.

    • Daylighting: Strategically placed windows and light shelves.

    • Shading: In Ghana, shading east and west windows entirely and using generous north/south overhangs can reduce cooling loads by $20\text{--}40\%$.\n * Active Design Strategies:

    • High-efficiency HVAC: Inverter-type units have higher Energy Efficiency Ratios (EER).

    • LED lighting: Uses $60\text{--}75\%$ less energy than fluorescent lamps.

    • Building Energy Management Systems (BEMS): Real-time computer-based optimization.

• Building Envelope and Thermal Performance Metrics

  • U-Value (Thermal Transmittance): Rate of heat transfer through a building element. Measured in $W/m^2K$. Lower values indicate better insulation. Target values in temperate climates are below $0.3\,W/m^2K$.

  • Solar Heat Gain Coefficient (SHGC): The fraction of incident solar radiation entering through glazing (ranging from $0$ to $1$). Lower SHGC is better for hot climates.

• Energy Conservation Measures (ECMs)

  • Envelope: Roof insulation, cool roof coatings, double-glazing, air sealing, solar shading.

  • Mechanical: Inverter AC units, variable-speed drives, HVAC zoning.

  • Lighting: LED relamping, occupancy sensors, daylight-linked dimmers.

  • Behavioural: Thermostat setback programmes, occupant education.

  • Well-implemented ECMs can reduce operational energy by $30$ to $60\%$.

• Renewable Energy Integration

  • Solar Photovoltaic (PV): A standard $1\,kWp$ system in Ghana generates $1,400 \text{ to } 1,800\,kWh$ per year.

  • Solar Thermal Systems: Can meet $60\text{--}80\%$ of annual domestic hot water demand.

  • Net Zero Energy Building (NZEB): Generates as much energy on-site as it consumes annually.

• Energy Performance Assessment

  • Energy Performance Certificates (EPCs): Ratings from A to G.

  • Building Energy Simulation (BES): Software like EnergyPlus or IES-VE.

  • EDGE Certification: IFC/World Bank group standard requiring $20\%$ savings in energy, water, and embodied energy. It is the most widely applied green standard in Ghana.

Chapter 2: Lifecycle Environmental Performance Assessment

• Introduction to Lifecycle Assessment (LCA)

  • LCA is a systematic, quantitative technique for evaluating environmental burdens throughout a product's life.

  • Governed by ISO 14040 (principles) and ISO 14044 (requirements).

  • Standards include EN 15978 for whole buildings and EN 15804 for Environmental Product Declarations (EPDs).

• The Four Phases of LCA

  1. Goal and Scope Definition: Purpose, system boundaries (e.g., cradle-to-grave), and the functional unit (typically $1\,m^2$ of net floor area per year for 50 years).

  2. Life Cycle Inventory (LCI): Collection of all inputs (energy, water, materials) and outputs (emissions, waste).

  3. Life Cycle Impact Assessment (LCIA): Translating inventory into indicators like Global Warming Potential ($kg\text{ CO}_2\text{-equivalent}$), Ozone Depletion Potential ($kg\text{ CFC-11-equivalent}$), and Primary Energy Demand ($MJ$).

  4. Interpretation: Reviewing results to identify significant contributors and assess robustness.

• Building Lifecycle Stages (EN 15978)

  • A1–A3 (Product Stage): Raw material extraction, transport to factory, and manufacturing.

  • A4–A5 (Construction Process Stage): Transport to site and installation.

  • B1–B7 (Use Stage): Maintenance, replacement, operational energy (B6), and water use (B7).

  • C1–C4 (End-of-Life Stage): Demolition and waste disposal.

  • D (Beyond System Boundary): Potential benefits from reuse and recycling.

• Whole Life Carbon: Embodied vs. Operational

  • Upfront embodied carbon (A1–A5) is released before occupancy and cannot be offset by future efficiency.

  • In highly energy-efficient buildings, embodied carbon can account for $50\text{--}80\%$ of whole life carbon emissions.

Chapter 3: Domestic Architecture in the Ghanaian Context

• Ghana's Climatic Zones

  • Hot-Humid Coastal Zone: High temps ($25\text{--}32^\circ C$) and heavy rainfall ($800\text{--}2,000\,mm/year$). Natural ventilation is the primary cooling strategy.

  • Hot-Dry Savannah Zone: Temps can reach $40^\circ C$. Diurnal range can exceed $15^\circ C$. High-thermal-mass construction and night ventilation are key.

• Characteristics of Ghanaian Residential Architecture

  • Traditional Vernacular:

    • Compound house plan: Rooms around a central open courtyard.

    • Earthen construction: High thermal mass buffers temperature extremes.

    • Thatched roofs: Insulative and breathable, yet fire-prone.

    • Verandas: Shaded transition zones.

  • Contemporary Housing: Dominated by sandcrete blockwork and corrugated metal roofs. This has low thermal mass and poor insulation, creating "thermally uncomfortable" environments.

• Low-Carbon Local Building Materials

  • Compressed Earth Blocks (CEB): Mixture of soil and $5\text{--}10\%$ cement. CEBs have $90\%$ lower embodied carbon than fired bricks.

  • Bamboo: Reaches maturity in $3\text{--}5$ years. Comparable to mild steel in tension when treated with borax.

• Urbanisation and Housing Demand

  • Urban population was over $57\%$ in 2020, growing at $3.4\%$ annually.

  • Accra faces a housing deficit of $1.7\text{ million}$ units.

Chapter 4: Building Regulations and Standards in Ghana

• Legislative Framework

  • The Buildings Act (1958): Outdated colonial legislation.

  • Local Government Act (1993, Act 462): Empowers MMDAs for development control.

  • Town and Country Planning Act (2016, Act 925): Modern land use governance.

  • Ghana Building Code (GBC) 2018: The first comprehensive national technical standard.

• Structure of Ghana Building Code 2018

  • Part A: Administration and permit procedures.

  • Part B: Structural design loads and foundation requirements.

  • Part C: Fire Safety (resistance ratings, escape routes).

  • Part D: Accessibility (Standards from Act 715/2006).

  • Part E: Environment (drainage and sanitation).

  • Part F: Energy (minimum U-values and AC efficiency).

• Environmental Regulations

  • Environmental Impact Assessment (EIA): Required for buildings over $5,000\,m^2$ or in sensitive locations (LI 1652, 1999).

  • Riparian Buffer Zones: Setbacks from watercourses ranging from $30\text{ to } 100\,metres$.

• Enforcement Challenges

  • $60\text{ to } 80$ percent of urban construction in Ghana is informal.

  • Reforms include digitalisation (E-permit systems), risk-based inspections, and incentives for compliance.

Chapter 5: The Nature-Building Relationship

• Ecological Impacts of Buildings

  • Land Transformation: Includes soil sealing and habitat fragmentation.

  • Urban Heat Island (UHI): Urban areas are $3\text{--}7^\circ C$ warmer than rural surroundings due to dark surfaces and canyon geometry.

  • Hydrological Alteration: Impermeable surfaces accelerate runoff and cause annual flooding, notably in Accra.

• Green Infrastructure Elements

  • Green Roofs:

    • Extensive: Shallow substrate ($60\text{--}150\,mm$).

    • Intensive: Deeper substrate (>150\,mm) for shrubs and trees.

    • Benefits: Retaining $50\text{--}90\%$ of rainfall and mitigating UHI.

  • Living Walls: Cool facades through shading and evapotranspiration.

  • Sustainable Urban Drainage Systems (SuDS): Permeable paving, bioswales, rain gardens, and retention ponds.

• Biophilic and Regenerative Design

  • Workplaces with biophilic features report a $15\%$ reduction in absenteeism, a $6\%$ increase in productivity, and a $15\%$ improvement in wellbeing.

  • Biodiversity Net Gain (BNG): Leaving biodiversity in a measurably better state ($+10\%$ ideally) after development.

  • Regenerative Design Spectrum: Moving from Sustainable (minimising harm) to Restorative (restoring conditions) to Regenerative (acting as a productive ecosystem participant).

• Climate Resilience Projections (2050)

  • Average temperatures in Ghana are projected to rise by $1.5\text{--}3.5^\circ C$.

  • Coastal erosion affects assets in the coastal zone, which are among the fastest-eroding in West Africa.