On sustainable building materials

  • March 28, 2024
  • Posted by: OptimizeIAS Team
  • Category: DPN Topics
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On sustainable building materials

Subject: Environment

Section: Sustainable development  

Context:

  • India is witnessing an unprecedented construction boom, with over 3,00,000 housing units erected annually. This growth brings economic opportunities and improved living standards but also poses significant environmental challenges.

Details:

  • The building sector, a major energy consumer, accounts for over 33% of India’s electricity usage, contributing to environmental degradation and climate change.
  • The India Cooling Action Plan forecasts an eight-fold increase in cooling demand between 2017 and 2037, emphasising the need for thermal comfort while reducing active cooling demand.

How can the construction sector become energy efficient?

  • The construction sector can increase its energy efficiency by focusing on reducing energy and cooling demands, exacerbated by economic growth, urbanization, and climate change.
  • Implementing measures like the Eco-Niwas Samhita (ENS) and the Residential Energy Conservation Building Code are pivotal.
    • Eco Niwas Samhita (ENS) is a Residential Energy Conservation Building code developed by BEE.
    • The code sets standards to limit heat gain and loss and ensure adequate natural ventilation and daylighting potential.
    • The Ministry of Power launched the Energy Conservation- New Indian Way for Affordable & Sustainable Homes (ECO Niwas) in 2018.
  • The ENS introduces the Residential Envelope Transmittance Value (RETV), a measure of heat transfer through a building’s envelope, advocating for an RETV of 15W/m2 or less to enhance indoor cooling efficiency, occupant comfort, and reduce utility costs.
  • Despite these guidelines, the prevailing construction practices rely on quick, energy-intensive methods emphasizing active cooling, compromising thermal comfort.
  • There’s a notable gap in awareness regarding climate-appropriate design and architecture, partly due to misconceptions about the initial costs of constructing climate-responsive buildings.
  • This highlights the need for a shift in perception and increased educational efforts towards sustainable building practices.

What materials are optimal?

  • In warmer climates across four Indian cities, the study found Autoclaved Aerated Concrete (AAC) blocks, red bricks, fly ash, and monolithic concrete (Mivan) to be popular building materials.
Building materialsDescription
1. Autoclaved Aerated Concrete (AAC) blocksAAC is concrete that has been manufactured to contain closed air pockets. AAC is one-fifth the weight of concrete.

AAC blocks can be used for loadbearing structures up to 3 storeys, and AAC panels can be used for cladding.

AAC has medium thermal mass and provides very good thermal insulation.

AAC is relatively easy to work with but can also be easily damaged. Specific construction techniques are required.

AAC used externally should be coated with a vapour-permeable, water-resistant finish. Render to blockwork must be a proprietary mix compatible with the AAC substrate.

2. Fly ashA by-product of combustion of coal in electric utility or industrial boilers.

  • It can be used as a building material for various purposes.
  • It’s commonly used as structural fill for road construction and fly ash can be used to make bricks, ceramic tiles, plaster, Portland cement, and ready-mix cement.
  • Other building materials that may contain fly ash include hot mix asphalt, grout fill, wallboard, concrete pipes, and concrete bricks.

Benefits:

  • Cost-effective alternative to Portland cement
  • Increases durability and workability of concrete
  • Helps prevent cracking or expansion and reduces permeability
  • Resistant to sulphates and alkali-aggregate reactions
  • Recycles coal burning waste and reduces CO₂ emissions

Challenges:

  • Longer drying and setting times
  • Delayed setting in cold climates
  • Slow strength development in cold climates
  • Air-entraining admixtures may be necessary
  • Requires safe disposal according to EPA regulations
3. Monolithic concrete or Mivan technology
  • Mivan Shuttering is a fast-paced construction technology which offers strength and durability to a building by use of Aluminum Framework System.
  • Mivan Technology reduces the construction time by almost the half in comparison to conventional practices. It minimizes the need of skilled labour and completely eliminates the labour intensive activities such as masonry and rendering.
  • On the structural front, the technology makes the buildings more seismic-resistant and durable, since there are lesser number of joints, the building faces reduced leakages, hence requiring negligible maintenance.

Comparison of these materials:

  • Monolithic concrete is preferred by developers for high-rise buildings due to its speed, strength, quality, and scalability, being chosen for over 60% of buildings currently in design and construction phases.
  • However, AAC blocks stood out in RETV evaluations, demonstrating the lowest heat transfer values across various climates, thus identifying them as thermally efficient.
  • Comparative analysis showed monolithic concrete has significantly higher embodied energy — 75 times more than AAC blocks for the same wall area, indicating a greater environmental impact.
  • Red bricks, while requiring the most construction time, have moderate embodied energy but contribute to resource depletion and waste.
  • Mivan technology, on the other hand, allows for the fastest construction, especially beneficial for taller buildings.
  • Despite the environmental and sustainability concerns associated with each material, AAC blocks emerge as a preferable option. They strike an effective balance between low embodied energy and efficient construction time, making them a more environmentally friendly choice compared to red bricks and monolithic concrete, which have higher embodied energies and associated environmental impacts.

Challenges and prospects:

  • Current reliance on materials like Mivan, despite its efficiency, poses sustainability issues due to its high embodied carbon and poor thermal comfort.
  • The challenge for the construction industry is to innovate and produce building materials that are not only cost-effective and scalable but also durable, fire-resistant, and offer excellent thermal performance and climate resilience.
  • There’s a need for interdisciplinary collaborations focusing on integrated design to improve aspects such as building orientation, Window Wall Ratio (WWR), U-value (heat transfer rate) of building components, glazing performance, and active cooling systems.

Source: TH

Environment On sustainable building materials