A new development in the planning stages in Allston is calling for the addition of a rooftop farm. Located at 44 North Beacon Street, the 54-unit residential project would boast 16 condos and 38 apartments ranging in size from studio to three-bedroom units. The green roof system would serve as an extension to the existing roof and would include plants as well as a drainage system, a root repellent system, a filter cloth, a light-weight growing medium and high-quality water-proofing. But what exactly is a green roof and what are the benefit and disadvantages of this type of system?
What is a Green Roof?
A green roof is a roofing system that involves placing some sort of vegetation on the top of a human-made structure, typically a building of some sort. A green roof system may be modular with a filter cloth, drainage layers and some sort of growing media with plants located in movable grids that are often interlocking. They may also be built-up with each component of the system installed separately. While green roofs are still relatively uncommon in the United States, they are well-established in Europe. This has led to a multi-million dollar market for green roof products in many European countries.
What are the Public Benefits of a Green Roof?
Green roofs provide a number of benefits to the public. These include:
- Aesthetic beauty
- Waste diversion
- Air improvement
- Moderation of urban heat
- Stormwater management
Due to the daily dew and evaporation cycle of plants, placing them on a roof helps to reduce the Urban Heat Island (UHI) effect, thereby helping the environment while also reducing the burden placed on HVAC systems. Green roofs can also help to reduce the distribution of dust and other particulate matter, thereby reducing the production of smog.
Green roofs can also assist with stormwater management, with 70 to 90 percent of the precipitation that falls during the summer being retained by the roofs. In the winter, they still retain 25 to 40 percent of the precipitation that falls on them. The water is then stored by the substrate and taken up the plant where it is returned to the atmosphere through evaporation and transpiration.
Of course, a green roof can also provide new amenity space to the area. This can be in the form of a community garden, commercial space or recreational space.
What are the Private Benefits of Green Roofs?
Green roofs also provide benefits to the owner of the building. Some of these benefits include:
- Improved energy efficiency
- Fire retardation
- Noise reduction
- Increased durability of the roofing membrane
Of course, a green roof can also be used to increase the marketability of a building. In fact, studies have shown that having a green roof assists with sales while also increasing property value due to the increased efficiency they provide.
The site for the Allston development was purchased by Boston Real Estate Collaborative in 2017 for $3.5 million. Construction of the u-shaped building, which will be seven stories tall when completed, is expected to be finished by 2021.