Eco-friendly green roof solutions: Investigating volcanic ash as a viable alternative to traditional substrates

This research investigates the potential of volcanic ash as a green roof material, focusing on its thermal conductivity, physical characteristics, and permeability. Laboratory tests were conducted to determine thermal conductivity under different moisture conditions using two measurement devices, TLS 100 and HFM 436/3/1 Lambda. The results revealed that thermal conductivity increases with higher moisture content, indicating improved heat conduction as the material becomes more saturated with water. Particle size distribution analysis demonstrated that the majority of volcanic ash particles fall within the range of sand and gravel, providing a porous and well-draining material. Sand-sized particles create interconnected voids, facilitating efficient water movement, while gravel-sized particles enhance structural stability and load-bearing capacity. The limited presence of silt-sized particles further validated the material's suitability for green roof applications. Permeability tests on loosely compacted volcanic ash revealed higher permeability at 0% compaction, aligning with intended green roof configurations. This high permeability ensures effective drainage, preventing water accumulation and promoting healthy vegetation growth. At 20% compaction, the material still effectively managed water under potential compaction forces, striking a balance between drainage and water retention. Visual examination of green roof samples demonstrated that volcanic ash substrates resisted weed growth due to the absence of fertilization. While the commercial substrate exhibited better vegetation development due to added nutrients, volcanic ash substrates supported vegetation survival throughout the summer period with an irrigation system, reducing maintenance and lifecycle costs. In conclusion, the research findings indicate that volcanic ash possesses desirable thermal properties, a suitable particle size distribution, and favorable permeability characteristics for green roof applications. Its potential as a sustainable and cost-effective alternative to commercial substrates is evident, offering resilient urban landscapes with reduced environmental impact. Further exploration and optimization could solidify volcanic ash as a valuable component in advancing green roof technologies, promoting sustainable urban development.