There are many myths and misunderstandings around sustainability in construction. First, the belief that what is sustainable must inherently be technological, complicated or out of reach. Or that the products will necessarily be more expensive, will be made of recycled materials or will not be so aesthetically pleasing. When it comes to material specification, there is often confusion. Is steel more sustainable than bamboo? Would it be better to use a material that is said to be sustainable, but which goes through numerous industrial processes, or one with a low level of processing? The answer is not so simple, and there are various comparison mechanisms to help guide us. But this is an important consideration to make, as one of the main ways the construction industry can help reduce its carbon footprint is to select materials with the lowest general contribution to emissions and environmental impact. Natural slate, which can be used for roofing and facades, is a great example of this.
The most commonly used methodology to understand the real impact of a product or service is the so-called Life-Cycle Assessment. This is a technique for the assessment and quantification of possible environmental impacts associated with a product or process, which compiles the inputs, outputs and overall potential environmental effects of a product along its life cycle. This covers the extraction and processing of raw materials, manufacturing, distribution, use, recycling and final disposal.
Some components are important to analyze, such as:
- The product's incorporated energy: All the energy required to extract, process and transport the material and deal with production waste.
- The durability of the material: The longer the durability, the lower the impact.
- Its potential for reuse, recycling or recovery.
If we apply these factors to natural slate, it performs well in all three. First, it is a product with low incorporated energy, as it requires only minimal processing when extracted. Once extracted, the rock is divided into the desired thickness and finalized. Its incorporated carbon value is 16%–at the most–of those of other roofing materials, although there is a large variation in incorporated carbon depending on the place of extraction and other factors.
Another key factor is its durability. The pieces can last up to 100 years, although it is common to have to replace a few. This causes the incorporated energy value to lower even more. In addition, it is an easily reused material. As explained by Cupa Pizarras, a world leader in natural slate, “this can be seen in conservation areas and in historic buildings in Scotland, where second-hand slates are still being used for repairs and maintenance, 60 years after the Scottish industry ceased to operate. Recovered slate stocks provide a ready source for locally available material.”
During its transformation process, slate requires less water, consumes less energy and pollutes much less than any other facade or roof material alternative. As an example, to be produced, slate consumes 6 times less energy than fiber cement or 135 times less water than zinc. This is why the independent database Inventory of Carbon and Energy (ICE, University of Bath), highlights natural slate as the material with the lowest amount of adverse impacts on the environment.
Natural slate can be applied as roofs, but also as rainscreen and ventilated facades. To learn more about the application of the slate on roofing and facades, visit Cupa Pizarras in our catalog.