A rooftop garden or a green roof can be as simple as containers and raised beds to roofs covered with soil and plants. While the terms are often used interchangeably there are differences which we explore below.
Green roofs can be as simple as a 2 inch covering of hardy groundcover or as complex as a fully accessible park complete with trees (not recommended for the traditional/conventional residential dwelling). While both green roofs and rooftop gardens provide environmental benefits, give sanctuary to animals and insects and do their part to improve air quality, a green roof is designed for maximum environmental benefits. By absorbing heat and acting as insulation, a green roof reduces energy needed to provide cooling and heating. While rooftop gardens provide shade and partial insulation, they will never provide the same benefits because rooftop gardens do not cover the entire roof of a building.
Other benefits of green roofs are: decrease in the production of associated pollution and greenhouse gas emissions by lowering air conditioning demand; and improving human health and comfort by reducing heat transfer through the building roof thus improving indoor comfort and lowering heat stress brought on by heat waves.
Green roofs focus on efficiency and lightness, while rooftop gardens are more aesthetic and created for their beauty or utilitarian purposes. Rooftop gardens can be created with the use of containers and raised beds and for far less than a green roof.
Though initially more expensive to install than conventional roofing, the financial benefits of a green roof are realized over the lifetime of the roof. The cover protection that a green roof provides means a longer life span compared to conventional roofing materials. Its natural insulation properties help buildings retain heat in the winter and protect the black tar from heating up in the summer thus reducing the energy needs for the building.
Regardless of whether you are installing a rooftop garden or a green roof there are certain issues to take into consideration.
- Care must be taken to ensure that the building is structurally sound and can hold the additional weight.
- Safety, for those on the roof and for those passing by on the ground. Ensure that equipment, containers and furniture are safely secured and that nothing is protruding upward from the floor of the roof.