Green roofs come with tons of benefits from sustainability, improved insulation, collecting stormwater, and reducing the effects of urban heat islands in big cities. But how much do they cost? Do you have to pay an arm and a leg to receive an ounce of the benefits of having a green roof? Today, we dive into how much it costs to install or replace a green roof and why it might pay off greatly in the end.
Benefits of Green Roofs
Green roofs are built on flat roofs to create a sustainable but functional green space on the roof. They feature a layer of soil or bedrock, grasses, and other low-level ground cover plants, and perhaps some rocks and concrete paths or seating areas to make it usable to residents or employees at a commercial property. They offer many benefits, including;
- Improved stormwater management
- Collects 80% of rainwater compared to 20% on standard roofs
- Energy cost savings
- Improves air quality
- Reduces greenhouse gas emissions
- Reduces urban heat island effects
- Improves building insulation
- Extends the life of your roof
- Opportunity for urban agriculture
- Provides home to local wildlife
- Provides a green space for residents or employees
- Easy to maintain — install and let it do its thing
For commercial building owners looking to improve sustainability practices and save money on energy costs, a green roof is ideal. They work great in urban areas by providing a glimpse of green in an otherwise concrete jungle.
Installing a Green Roof
Installing a green roof can vary greatly depending on the layout, the type of soil and plants used, and the plan to make it a functional space with seating areas and pathways. Green roof installation definitely a lot more planning and research compared to other types of flat roofs. You want to ensure you choose the right grass and plants to effectively provide you with energy cost savings and maintain a relatively self-sustaining system. In general, there are two types of green roofs: intensive and extensive, which we will detail below.
Intensive Green Roofs
The more time-consuming green roof is intensive. Intensive green roofs hold up to 150 lbs per square foot, so they require a building to withstand that. They are also much more like a garden where the owners choose various types of plants that require more care and tending. This type of green roof is exceptionally great for roofs used as an entertaining space or to maintain a rooftop garden. As the name suggests, caring for it is far more intensive and requires diligence in choosing which plants to plant and caring for them regularly.
Extensive Green Roofs
On the other hand, extensive green roofs are more self-sustaining and are planted using local plants that can grow and sustain themselves on their own as they would in the wild. This means choosing grasses and ground-cover plants that are non-invasive that can live and thrive with just an annual weeding and fertilizing. It’s important to choose native plant life that is also drought-tolerant to ensure the roof can sustain itself while insulating the building and doing its job as an efficient roof. These extensive green roofs are strictly for a green roof’s environmental and economic benefits and not so much for functionality.
Green Roof Installation Costs
Green roofs can be costly depending on the type of green roof installed, the square footage, and the landscaping going into it. A/nd extensive green roof will be the most economical option as it generally requires a simple layout (if not the entire roof area), some soil, planting the native species of plant, and letting it maintain itself. The intensive roofs are much more expensive due to the high maintenance required to maintain and the higher cost of purchasing more customized plants and vegetables to plant.
Factors that affect the cost of your green roof include location or climate, the quality of the roofing membrane underneath, how accessible the roof is, how much weight it can hold, cost of construction and installation (varies by contractor), and maintenance costs. These can all drive up the cost of your green roof replacement.
Choosing to go with an extensive roof can save a ton of money upfront and in the long run. Recover Green Roofs out of Boston determined that intensive roofs cost anywhere from $20 to $200 per square foot, while the most cost-effective extensive roofs are closer to $10 to $50 per square foot. Keep in mind that installing a green roof can extend the life of your roof by 300% or more when well maintained. That’s a long time and a lot of cost savings if done right.
If you are still struggling to decide whether to go with a green roof vs. a standard flat roof option, some tools can help. The University of Arizona created this green roof calculator to determine the energy performance (and cost savings) associated with your green roof. You can also compare the cost of green roofs to other flat roofs or other roofing materials for consideration here.
