Site Selection and Materials (Leaving Cert Construction Studies): Revision Notes
Sustainability and passive design: Site selection and materials
Understanding environmental sustainability
Environmental sustainability examines how human activities affect the natural world. Every process, material, and action we take impacts our surroundings. Current concerns about climate change, resource depletion, and carbon dioxide emissions make it crucial to take responsibility for our environmental impact.
The greenhouse effect occurs when gases in the atmosphere trap heat from the sun, causing Earth's temperature to rise. This happens when fossil fuels are burned, creating holes in the ozone layer. Building construction contributes significantly to this problem through material production and energy consumption.
Sustainable development principles
Sustainable development means meeting today's needs without preventing future generations from meeting their own needs. This approach requires considering long-term environmental impact rather than just immediate benefits.
The "cradle to grave" approach examines how materials are made, transported, used, and disposed of throughout their entire life cycle. This comprehensive view helps identify environmental impacts at every stage of a building's existence, from initial design through to eventual demolition and disposal.
Site selection for sustainable buildings
Design philosophy
Site selection for sustainable housing differs significantly from conventional approaches. Traditional methods adapt the site to suit the building through landscaping, access changes, and topographical modifications.
Sustainable housing takes the opposite approach - the building is designed around the existing site.
This philosophy means working with natural features rather than against them. For example, if a tree exists in the middle of a site, sustainable design incorporates it into the building rather than removing or relocating it. This approach reduces environmental disruption and maintains the site's natural ecosystem.
Carbon footprint reduction
Plants and grasses can be integrated into building designs to help offset their carbon footprint - the amount of CO₂ emissions produced through energy use, transport, and lifestyle activities. Green roofs and living walls are practical examples of how vegetation can be incorporated to reduce a building's environmental impact.
Sustainable and renewable materials
Material classifications
Sustainable materials are products that either come from waste from other industries, are renewable, or have a low carbon footprint (meaning minimal fossil fuel energy was used in their production). These materials help reduce environmental impact whilst maintaining building performance.
Renewable materials form a subset of sustainable materials. These can be produced indefinitely because they can be replenished naturally. When a tree is cut down, another can be planted to replace it. Plants and biomass are prime examples of renewable building materials.
Straw bale construction
Straw, grass, and reeds have been traditional building materials for centuries. Modern sustainable building practices are reviving these materials, combining them with contemporary construction methods to create more environmentally friendly homes.
Construction methods
There are several approaches to straw bale housing:
- Some use straw bales as structural elements that bear the building's weight
- Others create wooden frames for structural support and use straw as insulation within the walls
Advantages of straw bale construction
- Cost-effective: Relatively inexpensive compared to conventional materials
- Renewable resource: Straw can be continuously harvested
- Good insulation properties: Provides effective thermal performance
- Readily available: Agricultural waste product that's widely accessible
Disadvantages of straw bale construction
Key Challenges to Consider:
- Moisture susceptibility: Can rot in damp conditions without proper protection
- Bulky material: Requires thick walls, reducing internal space
- Limited acceptance: May face building regulation challenges in some areas
Zinc roofing
Zinc is gaining popularity as a sustainable roofing material for environmentally conscious buildings due to its beneficial properties and environmental credentials.
Material properties
Building-grade zinc sheeting combines zinc with copper and titanium to maximise flexibility and strength. The material is typically joined with seamed connections and offers several unique characteristics:
- Self-healing: Over time, zinc develops a protective layer that provides waterproofing and chemical resistance
- Malleable: Can be shaped into designs impossible with traditional slate or tile roofs
- Durable: Lighter than slate whilst maintaining long-term performance
Environmental advantages
- Low toxicity: Safe for human health and environmental exposure
- Highly recyclable: Nearly 100% recyclable because it doesn't rust or degrade significantly
- Clean water runoff: Doesn't contaminate soil or groundwater with harmful chemicals
- Low manufacturing cost: Recyclability reduces production expenses
Economic considerations
The primary disadvantage of zinc roofing is its high initial cost - approximately twice the price of conventional tiles or slates. However, its longevity and recyclability may offset this expense over the building's lifetime.
Energy efficiency in sustainable design
Energy efficiency focuses on reducing the amount of energy needed to provide building services and comfort. This involves identifying wasteful energy uses and implementing solutions to minimise consumption.
Common energy waste occurs when heating systems operate whilst windows remain open, as the heated air simply escapes outdoors. This represents a clear example of how poor coordination between building systems can lead to significant energy loss.
Effective sustainable design addresses such inefficiencies through:
- Improved airtightness: Preventing uncontrolled air leakage
- Enhanced insulation: Reducing heat transfer through building fabric
- Controlled heating systems: Operating heating only when and where needed
- Efficient appliances: Using equipment that minimises energy consumption
These measures work together to create buildings that require less energy for heating, cooling, and operation whilst maintaining comfortable living conditions.
Key Points to Remember:
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Sustainable site selection means designing the building around existing site features rather than modifying the landscape to suit the building
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Sustainable materials include waste products from other industries, renewable resources, or materials with low carbon footprints from production
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Renewable materials like timber and straw can be continuously replenished, making them environmentally preferable to finite resources
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Straw bale construction offers good insulation and cost benefits but requires careful moisture management to prevent deterioration
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Zinc roofing provides excellent durability and recyclability but comes with high initial costs that may be offset by long-term performance