Roofs are our unsung heroes, providing protection for people and assets, giving character to individual buildings and meeting the challenge of every new day: weather events, foot traffic, climate changes. Over the years, roofing has evolved immensely from the types of roofing materials used (thatch and reed back in time), to the advancement of construction practices. Functionally, a flat roof protects a building’s structure. Green roofs however, deliver additional benefits. They not only absorb rainwater and provide insulation but yield private and public benefits, promote human connection, reflect environmental and social conscience and provide solutions to urban heat island effect. Sound like a tall order? Read on.
Green roofs are partially or completely covered with vegetation planted over a waterproofing membrane and potentially a root barrier, drainage and irrigation system. There are several types of green roofs including:
EXTENSIVE:
- Relatively shallow with a depth of 3-5 inches
- Lightweight roof system
- Low/minimal maintenance
- Common plant choices include mosses, sedums, herbs, succulents and low-growing grasses (drought tolerant plans with shallow root systems)
- Lower cost to create/install
SEMI-INTENSIVE:
- Depth of 5-7 inches
- Medium weight roof system
- Mid-range maintenance and cost to create and install
- Supported plants include select perennials, sedums, ornamental grasses, herbs and little shrubs
INTENSIVE
- Thicker depth of 7-24+ inches
- Heavier roof system
- Higher maintenance including regular irrigation
- Can support a variety of plant life including shrubs, small trees, perennials, lawn, rooftop farming
- Most expensive to create/install
Urban greening is a means to beautifying building structures and an identifiable signal of the green building movement. For many developers and landlords, a green roof provides new space for innovative and attractive amenities with public and private benefits.
For commercial enterprises, accessible green roofs provide an opportunity to differentiate their facilities, and increase perceived value and marketability. Rooftop amenities available to building tenants can include co-mingling spaces, patios and restaurants, along with architectural landscaped areas. Such amenities provide great spaces for employees to relax, and culturally, is good for business.
Green roofs are thought to be good for the community, decreasing stress through their pleasing landscapes, giving myriad opportunity for human connection and reconnecting us with nature. Community structures with green rooftop spaces often serve as community hubs allowing for local food production such as co-op’s, providing improved levels of nutrition and empowering the local community. Young people benefit from recreational facilities, playgrounds, and the opportunities living roofs provide to learn about plants, green roof benefits and roofing technology.
Planting the rooftops of urbanized areas brings many environmental benefits including improved energy efficiency through reduced cooling and heating costs. Green plant life helps to capture airborne pollutants and filter noxious gases which improves the health and wellbeing of people. And the benefits extend beyond humans, considering green roofs provide good habitat for a variety of insects and wildlife.
Green rooftops help to moderate and lower urban heat island effect, which is defined as an urban area that is warmer than the surrounding rural areas due to human activity. Dense downtown areas and paved surfaces amplify and trap heat and can drive temperatures up dramatically with negative consequences such as higher air pollution, reduced nighttime cooling, and negative effects on human health. Green rooftops help to moderate and lower urban heat island effect through the cooling effect of the dew and evaporation cycle, and by light that is absorbed by rooftop plants and vegetation (instead of being converted into heat energy).
Popular in Europe, green rooftops are gaining attention in North America as urban planners look for socially responsible ways to mitigate diminishing natural spaces and increase the environmental attributes of city landscapes. At ILD, we’re pleased to have tested green roofs around the world, including some of North America’s most iconic sites: the 9/11 Memorial Plaza, the Library of Congress Packard Campus, Soldier Field and Maggie Daley Park. Because vegetation and amenities will cover the rooftop membrane, it’s critical to conduct testing for water tightness before installation of the green roof and again after the overburden is laid. It is also wise to consider ongoing intelligent rooftop monitoring technology to protect the investment and provide peace of mind well into the future.
View some of the world’s most interesting green roofs here: https://www.architecturaldigest.com/gallery/green-roof-living-roof-designs