Known as living roofs, eco-roofs, and vegetated roofs, green roofs offer many benefits to the user. The process of growing living plants on the roof of a home or building has been shown to dramatically decrease cooling costs for the building while enhancing stormwater management and air quality for the area.
There are several types of green roofs, which leads to a wide range of associated costs. The average homeowner, creating an extensive green roof for a 1,500sq.ft. roof, can expect to spend between $15,000 and $30,000, with most paying around $22,000 for the project.
Green Roof Installation Cost | |
---|---|
National average cost | $22,000 |
Average range | $15,000-$30,000 |
Low-end | $12,000 |
High-end | $40,000 |
Most people consider three basic types of green roofs, along with two subsets that may be used in special cases. For residential purposes, only extensive roofs are an option, unless installing on a multi-residential building.
Type of Green Roof | Average Cost |
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Extensive Roof | $10 to $20 per sq.ft. |
Semi-Intensive Roof | $15 to $30 per sq.ft. |
Intensive Roof | $25 to $35 per sq.ft. |
Blue-Green Roof | $25 to $35 per sq.ft. |
Bisolar Roof | $25 to $35 per sq.ft. |
An extensive green roof is the most common and least expensive type of green roof, with costs ranging from $10 - $20 a square foot 1. They consist of a thin layer of soil, with continuous coverage of growing material. They are fairly lightweight and can be installed on roofs with a pitch from 0º to 30º. They are virtually maintenance-free once set up and do not require irrigation.
A semi-intensive roof is often referred to as a rooftop garden. It is heavier than an extensive roof and usually has plants in modular containers rather than free-growing. When constructed on a concrete roof, visitors can walk around the growing medium. Costs start at $15 a square foot 1 and range to about $30 a square foot 1. They require more care and maintenance, as well as irrigation, but can provide a more sculpted appearance.
Intensive roofs are very heavy, with a thick layer of soil. They allow the most customization for the rooftop but are the most expensive, with costs ranging from $25 - $35 a square foot 1. They must be installed on a flat, concrete roof and require a lot of care and maintenance as well as irrigation. These are not normally practical for residential buildings but can produce extremely dramatic and beautiful results.
The blue-green roof is designed for city usage in areas that see very heavy rainfall and need rain storage and management. They combine rain storage techniques with green roof technology, so they have fewer plant options. They require a flat, concrete roof that can bear the weight. They cost $25 - $35 a square foot 1.
A biosolar roof is a green roof that has solar panels installed. It may be intensive or semi-intensive and usually has modular growing mediums rather than complete coverage. The green roof portion costs between $25 - $35 a square foot 1, with the solar panels costing an additional $18,000 - $20,000. They are not normally installed on residential roofs due to the weight.
The pitch of your roof dictates, in part, which type of green roof system you can use and whether you can install a green roof system at all. Intensive green roofs must be installed on concrete roofs that have 0º pitch. Extensive green roofs can be installed on roofs with a pitch up to 30º but preferably less than 20º. The closer to flat the roof is, the easier time you will have installing the growing medium and plants.
Depending on the type of green roof you choose and the pitch and material of your roof deck, you may be able to have either a modular or built-in 2 system. Modular systems involve using plants in trays, so you can better customize the appearance of the roof and create walking paths. The trays, however, are usually heavier and reserved for commercial buildings with concrete roof decks and intensive systems. Extensive rooftops are generally built-in 1 with total coverage because they are lighter and can be installed on a variety of roofs, including those with moderate pitches and standard plywood 3 roof decks.
Tray systems are used for extensive and semi-intensive roofs, and they feature a thin layer of soil or planting material contained within the system. The tray acts as a barrier between the plants and the structure beneath, preventing any excessive growth, protecting the roof, and keeping the plants secure and locked together in an enclosed system. Costs of a green roof tray system range from $10 to $30 per square foot.
Labor makes up a significant portion of the cost of a green roof, mostly because the process of creating one can be labor-intensive. Getting the materials onto the roof, constructing the layers, and installing the plants is extremely time-consuming and can cost $5 to $10 a square foot 1 in labor.
Roofs with a steeper pitch or have very intricately designed patterns for growing cost significantly more than roofs that have seeds mixed into the growing medium prior to installation. For a 1,500 sq.ft. roof, expect the labor portion to make up roughly $10,500 of the $22,000 total.
Green roofs are essentially built up or installed in layers. Every installation should start with an assessment from a structural engineer to determine how much the roof can hold per foot 2. Not every roof is a good candidate, and some roofs require substantial work before installing a green roof.
A roof barrier, which is usually a type of heavy plastic, is spread over the roof to make sure that the roots do not penetrate the roof deck. If the roof has walls or if there will be walking paths, these are lined with some kind of gravel. Then, the moisture retention layer is placed, which looks similar to egg crating. A filter fabric goes on top of this, which is what will hold the growing media or soil.
Soil is placed on the filter fabric, and then the plants are installed. This may be done through seeds, by planting seedlings and small plants, or by installing trays of ready-grown plant material. Installation takes place over roughly 5 to 7 days, but it will take several weeks for the plants to establish themselves.
Plants for a green roof vary, depending on the area where you live and your climate. Just like plants that grow in the ground, the plants for your green roof do best if they grow well in your climate. Wildflowers and sedum do best, but you can also plant grasses and a range of other plants. Some of the better choices include aromatic herbs, clover, groundcover, and succulents. For an extensive green roof, the plants should be able to grow in under 5 inches of soil. Plants for an intensive green roof may be able to have a deeper root system.
Extensive green roofs, which are most often used for residential homes, do not require watering. However, semi-intensive and intensive roofs do. In most cases, you need an irrigation system 4 designed into the roof itself, both for drainage and to allow for proper irrigation and spread so that all plants receive the correct amount of water. Also, you do not want any large puddles of water. This can be done through tubing as well as by using water-storing mats. It is also important to note that many green roofs rely on plants like succulents because they store water and do not require as much irrigation. So, natural rainfall may be all that is needed.
Green roofs have numerous benefits for the user. They have been shown to reduce cooling costs for buildings by as much as 25%. They also help manage stormwater runoff in areas with a lot of rainfall and can improve air quality when installed in urban environments or on large, city-wide scales.
Green roofs are also attractive, and some can be very low-maintenance, extending the lifespan of the roof itself. However, the setup costs for a green roof are high. They are expensive, and more intensive green roofs can only be created on concrete roof decks that can handle their extreme weight.
While many people like the idea of a rooftop garden, it is not easy or possible to achieve in most residential settings. In the winter months, a green or living roof may not look as attractive because the plants may not be evergreen. Intensive green roofs set up on commercial buildings also require a lot of maintenance and irrigation to help them stay their best.
Green Roof Maintenance Costs
The amount of maintenance your green roof requires has a lot to do with the type of roof and plants you install. An extensive roof that is well-established does not require a lot of ongoing maintenance. You may want to fertilize it occasionally or water it in times of drought. Otherwise, extensive roofs are relatively self-sustaining.For an extensive roof, expect to pay $0.75 to $1 per square foot in maintenance costs each year.
Intensive roofs, however, need more work. If you have a rooftop garden, it may require the same level of care as any decorative garden bed. You also need to irrigate regularly and check to ensure that the drainage systems are operating properly. Your roof should be inspected regularly to make sure that it holds the weight of the green roof properly with no moisture problems or leaks. For an intensive roof, annual maintenance costs range from $1 to $1.50 per square foot.
When comparing the costs of green roofs and conventional roofs, it is important to look at both the short-term and long-term costs. In the short term, green roofs are more expensive than conventional roofs because the installation and material costs are higher overall. However, in the long term, having a green roof can actually save you money compared to a conventional roof.
A green roof provides insulation to the home, reducing the energy needs and thereby lowering the amount of money you spend on utility bills during the year. Not only that, but a green roof also protects the roof structure from things like the sun, rain, and snow, extending the lifespan of your roof and minimizing the amount of repairs that need to be done. General maintenance costs are also lower for green roofs than conventional roofs, and studies have shown that green roofs can save home and building owners thousands in the long term when compared to conventional roofs.
Unless you have a new roof installed to support a green roof, your existing roof should be inspected prior to installation. Roofing inspections cost anywhere from $50 - $500, depending on the size and level 5 of inspection.
Green roofs often outlast conventional roofs by many years. The exact length of time depends on many factors, such as the type of green roof, climate, and building type.
You do not need to mow a green roof, and most are fairly low-maintenance.
A green roof is made up of layers that help protect the roof from moisture, followed by soil and living plants.
Green roofs help reduce cooling costs for the building, manage stormwater runoff, and improve air quality.
This depends on the type of roof. Generally, only intensive green roofs can be walked on.
Cost to install green roof varies greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.