Thermal insulation

Lakshagriha – the Palace of Lacquer – finds its mention in the Sanskrit epic of ancient India, Mahabharata. It was a palace designed for the Author: Gaurav Srivastava, Assistant Professor, Civil Engineering, IIT Gandhinagar. Pandavas by the Kauravas with highly inflammable material, lacquer, and was meant to annihilate the Pandavas in their sleep. Those who have seen lacquer work (e.g. in bangles and artefacts) may recall that it burns with a vibrant flame and melts as it burns just like wax. Most modern buildings utilize energy efficient envelops, also called the façade system or curtain wall system. These façade systems have two main purposes: first is to render a visually distinctive and attractive exterior to the building and second, and perhaps more important, is to provide thermal insulation to the building. Thermal insulation is a crucial component in the design of HVAC systems and the overall energy consumption can be reduced significantly if the building being air conditioned is insulated well from the surroundings. Low energy consumption is a crucial parameter for a building to be considered green. Insulating materials are categorized by their so-called R-value – a measure of how well a material resists the flow of heat. The greater the R-value, the better a material is for thermal insulation. Typical polymeric materials used for insulation such as polyurethane (PU), and extruded expanded polystyrene (XPS) have R-values ranging between 5-8 ft2.°F.h/(BTU.in). While these materials are excellent insulators, they are highly inflammable and easily catch fire in temperatures between 300-400 °C (lacquer burns at around 250°C). Consequently, naïve use of such materials can lead to large-scale and uncontrollable building fires. The most notable recent fire involving the façade system occurred on 14th June 2017 at the Grenfell tower in London, which completely gutted the newly installed insulation and façade system worth GBP 12 million. The whole building burnt for more than 24 hours and caused casualties, severe injuries, panic, and economic setback. Indian buildings have also witnessed façade related fires in recent times. Recent research studies held at IIT Gandhinagar showed that a fire initiated at the ground floor of a building with an inflammable façade system can reach the second floor in 5 minutes. Fate of a combustible facade system after a test fire at the facade testing facility at IIT Gandhinagar While we are continually building taller and greener buildings, perhaps it is time to pause and assess the materials we choose for the new buildings. It is worth noting that the use of non-combustible materials in facade systems is gaining popularity, which is a good sign. The key, however, lies in how well we adapt our building design to include such materials. As well all know, there are no free lunches, and materials with enhanced fire behaviour may come at a greater cost. Are we as a society, willing to invest a little extra to save lives? Even if one decides to go this extra mile, there are always doubts on the performance of new materials due to the lack of proper building codes in India when it comes to fire performance of facade systems. Thus, the choice of right materials, appropriate design, and proper execution with sufficient attention to details, is the need of the hour. Efforts from all stakeholders – architects, engineers, policy makers, regulators, contractors, educators and end users – will be required to ensure that we are not building modern lakshagrihas for ourselves and for the future generation.

Thermal insulation

Dealing with Modern Lakshagrihas