Green Roofs Made Lighter

Vegetated green roof not only adds aesthetic value but also play a pivotal role in sustainability goals, managing rainwater runoff and mitigating the heat-island effect. They also serve as thermal buffers for the building underneath, cooling the buildings during warm weather and insulating them during cold weather. For these reasons, the global market for green roofs is set to increase by over 8 billion dollars by 2027.

However, incorporating green roofs into urban landscapes presents challenges, particularly supporting additional dead loads these systems create on roof structures. Lightweight aggregates (LWA), like expanded shale, clay and slate (ESCS), solve this challenge while contributing to vibrant and effective rooftop gardens.

Lightweight Aggregate Reduces Dead Load on Roof Gardens

Saturated and drained ESCS green roof media weighs approximately 75-90 pounds per cubic foot (pcf). This is because ESCS aggregate’s kiln-fired manufacturing results in an unconnected network of pores that helps substantially lower its density and weight.

Being lighter, the media allows design teams to reduce dead loads from a green roof than would have been possible with conventional soil mixtures. As a result, ESCS aggregates improve the possibility of achieving vegetated green roofs on retrofit projects where existing structures may not support heavier loads, increasing green cover in urban areas.

ESCS as a Planting Media on the Rooftop

Combining ESCS with organic soil components creates a lightweight yet robust soil medium that is an ideal planting media for green roofs. Because the aggregate is produced by expanding and vitrifying the select materials in rotary kilns, its interstitial voids act like tiny reservoirs that absorb and store moisture and water-soluble nutrients, creating a sustainable environment for plant growth. In fact, the angular nature of ESCS promotes uniform water retention and oxygen penetration, resulting in healthier plant roots.

For example, the extensive four-acre green roof on the Nashville Music City Center utilized lightweight expanded clay aggregates with varying organic components. The application fostered plant growth in the urban landscape which helped mitigate the heat island effect and offered a welcome respite for birds and insects. It also helps reduce stormwater runoff.

Stormwater Management Made Possible With ESCS LWA

ESCS LWA on green roofs can help facilitate low-maintenance stormwater drainage. The material allows for more efficient infiltration and greater water-holding capacity, slowly releasing moisture as the surrounding soil dries. Taking this on-site approach to stormwater management not only aids a structure’s environmental goals but also reduces the pressure on a city’s stormwater infrastructure.

The Nashville Music City Center benefited from ESCS’s stormwater management properties including filtering and collection of over three million gallons of stormwater in 2019, reducing the center’s municipal water usage by 51 percent. The application contributed to the project’s LEED Gold certification.

For the People and the Planet

ESCS LWA’s lightweight properties and water absorption capabilities not only ensure structural integrity but also foster thriving rooftop ecosystems. In fact, the ESCS mixture offers a sustainable and practical solution for a variety of low-impact, green infrastructure applications that benefit both people and the planet.

To learn more about ESCS for your project needs, contact us today.