Green Buildings are a subset of Sustainable Buildings. Hence, a green building may not necessarily be a sustainable building.
Green buildings requires an integrated design approach and should include the following specific performance aspects
- Structural design efficiency
- Energy efficiency (Fuel consumption of non-renewable fuels)
- Water efficiency
- Land consumption
- Materials & resource efficiency
- Greenhouse gas emissions
- Impacts of site ecology (environmental protection)
- Waste Management (Solid waste / liquid effluents)
- Indoor air quality, lighting, acoustics
- Longevity, adaptability, flexibility
- Operations and maintenance
Sustainable buildings should be neutral with regard to greenhouse gases, habitat, biodiversity destruction and water use (Fuller and Tayler, 2010). Sustainable buildings will include all of the above but differs in that it questions the ability to achieve green building performance indefinitely. Sustainability implies a regenerative capacity to sustain itself forever. Sustainable buildings also include
- Social and economic considerations
- Urban / planning issues
As per the three pillars of sustainable development, the challenge is to reach social sustainability, economic sustainability and environmental sustainability. This translates in housing development to be ‘cultural and social household requirements, affordability for initial and ongoing costs with reduction in climate change contributing factors such as greenhouse gas emissions, resource intensive building inputs, etc. Consumer demands and societal needs will impact the development of sustainable housing to create customisable construction to suit occupant needs, affordable construction of zero carbon construction and housing. This can only be achieved through an integrated design approach that looks at all levels of the building life cycle.
Consumers will demand affordable customisation. They are no longer satisfied with generic, monotonous products; rather, they prefer to purchase customised products.
Producers will require a marketable and reproducible green home. Semi-custom homes with moderate standardisation and customisation. Mass Custom Home as separate from a ‘ready built-home, semi-custom home and a home.
Society will demand ecological responsible design and green products.
Four influences on construction projects will be COST (affordability), QUALITY (design/product quality) and TIME (fast and on time)
Context of sustainability and sustainability models has been previously explained. Similarly, sustainable construction has also evolved.
Sustainability requires the following criteria and sub-criteria
- Engineering: Functional, Performance
- Economics: Expenditures, Revenue, Investment in innovation and R&D
- Environmental: Resource use (land, materials, energy), Residuals (impact on biosphere, air, water, land)
- Social: Health and safety, accessibility, acceptability
The framework for assessing infrastructure systems
Life cycle of a building
According to Crawford (2013) sustainable buildings must
- Resources consumed at or less than the rate at which they can be replenished
- Damage to the environment at or less than the rate at which it can naturally recover
Activities included in a building’s life cycle include: raw materials, transport, construction, banking, insurance, communications, marketing, etc.
Sustainable construction requires the review of the greenhouse gas emissions throughout the production of buildings. greenhouse gas emissions are present as embodied energy, in transport, operationally and in the disposal of related waste.
Embodied energy is present in all the stages, both direct and indirect. Treloar (1997) defined embodied energy as ‘the resources (energy, water, raw materials) required by all the activities associated with a production process and the share of resources used in making equipment and other supporting functions (direct and indirect)’.
Steps to quantify embodied energy:
- Specify materials or products (types and quantities)
- Multiply each material quantity by respective embodied energy coefficient
- Sum the embodied energy
As a rule of thumb, the energy efficiency of buildings can be generalised as follows:
- Building structure ~40%
- On-site input energy < 5%
- Transportation < 5%
- Road transport: Embodied energy is about 4 times more than shipping
- Reused materials up to 95% saving of embodied energy compared to virgin materials
- Recycled materials up to 90% savings of embodied energy
Place to get recycled building materials
Typical embodied energy for anew commercial building is 20 to 30 GJ/m2 and new residential property is 10 to 20 GJ/m2. The average house is ~ 240 m2
Embodied energy of an average house = 15 GJ/m2 * 240 m2 = 3600 GJ.
This is equivalent to 111 111 L of petrol energy:
3600 GJ / 0.032.4 GJ/L (energy density of petrol) = 111 111 L
Equate to ~ 1, 400, 000 km travel by car (1 L = ~12 km)
The earth’s circumference is 40,075 km so this would equate to travelling almost 35 times around the world.
Annual life cycle greenhouse gas emissions (LCGHG)
Where L: Service life of the construction (yr)
GE: Embodied GHG emissions (kg CO2-e)
GT: Transport GHG emissions (kg CO2-e)
GO: Operational GHG emissions (kg CO2-e)
GD: Disposal GHG emissions (kg CO2-e)
Embodied GHG emissions (kg CO2-e)
ai: EE per unit of each material (kg CO2-e/ kg) -aka- CO2 intensity ratio
Mi: Mass of each material (kg)
Transport GHG emissions (kg CO2-e)
bi = EE per unit of each material (kg CO2-e/ kg)
Di = Distance of transport (km)
Mi: Mass of each material (kg)
Operational GHG emissions (kg CO2-e)
ci: Full fuel cycle emission factor of each type of energy used(kg CO2-e/ MJ)
E: Annual operational primary energy consumption (MJ/yr)
Gr: Annual GHG from solid, liquid & gaseous residues from operation (kg CO2-e/ yr)
Disposal GHG emissions (kg CO2-e)
dk: Disposal GHG emissions per unit of each material (kg CO2-e/kg)
Mk: Mass of each material (kg)
This value could be negative or positive