Intensive Green Roof Cost Per Square Foot
The cost to install an intensive green roof ranges from $20 to $40 per square foot. These roofs require more planning, installation, design, and maintenance and, as such, could cost upwards of $200 per square foot or more. Intensive roofs are more common in cities, such as on the top of an apartment building or large corporate office.
In some circumstances, you can install a semi-intensive green roof. A semi-intensive roof is similar to a rooftop garden and runs as low as $15 per square foot.
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Benefits Or Green Roofs
Green roofs offer a number of hydrologic, atmospheric, thermal and social benefits for the building, people and environment:
- Reduces the volume and speed of stormwater runoff leaving the site
- Improves the quality of water that returns to the storm system and watersheds
- Reduces ambient air temperatures and increases humidity levels in the surrounding areas
- Filters and binds dust particles, filters airborne toxins to improve air quality
- Increases energy efficiency
- Increases building roof membrane life by protecting the underlying components against ultraviiolet and thermal degradation
- Provides habitat for a diversity of wildlife species
- Increases aesthetic appeal and useable green space for tenants
- Increases property value
Benefits Of A Green Roof
Green roofs can be pricey, especially if youre retrofitting your house to accommodate one. But if you have the means, they pay off economically, environmentally and aesthetically.
I think the number one reason homeowners get them is the cool factor, says Mumford. Would I rather look at an ugly garage roof from my second-story bedroom window, or a green roof thats obviously sustainable?
Some other benefits of green roofs include:
Developers and contractors can also benefit from incorporating green roofs into buildings. If a development requires green space, sometimes a green roof qualifies, allowing more surface room for parking and other needs. Green roofs can also ease compliance with stormwater retention codes.
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Do Green Roofs Reduce Flooding
Since green roofs contain living plant life, they readily absorb rainwater on impact.
The soil and vegetation act like a sponge, soaking up the rain before it runs off onto the ground.
Since they capture such a large concentration of water, these roofs significantly reduce the amount of rain that accumulates on the ground, reducing the chance of flooding in the nearby surrounding area.
Soak Up The Rain: Green Roofs
Green roofs have a layer of plant material that absorbs water like a sponge. They capture water when it rains, slowly releasing it through evaporation and plant use. Green roofs can significantly reduce the amount of rain water that would otherwise run off an impervious roof surface. Green roofs can also help reduce building energy usage and noise levels while increasing the durability and lifespan of the roof compared to conventional roofs.
Green roofs are being increasingly used in urban areas where space constraints limit the use of other stormwater management practices.
Note: Structures must be able to support the loading of green roof materials under fully saturated conditions.
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Operation & Maintenance Costs
Its important that you understand how green roof maintenance is carried out.
Consider the following:
- Is your maintenance performed by you or by a 3rd party?
- What materials need to be replaced?
- How is the climate in your area?
- What plant species do you have?
- How much irrigation do you need to perform?
Although there is no data related to maintenance cost reduction over the years, usually extensive green roofs require less maintenance than intensive green roofs.
In the first years, green roofs usually have more irrigation needs and re-planting may be needed due to plant inadaptation.
The below figure shows the operation and maintenance costs of extensive, semi-intensive, and intensive green roofs obtained from the following .
The average maintenance costs vary significantly from country to country and are as follows:
- Extensive green roof -4,28 /m2/year
- Semi-intensive green roof 7,77 /m2/year
- Intensive green roof 5,64 /m2/year
Eco Green Roofs And The Environment
The green roofs attractive appearance also has serious eco benefits. This environmental angle is whats helping to fuel the green roof trend across the world. From private residences to commercial properties, eco green roofs are popping up everywhere.
Even cities like London are pushing for their construction throughout the centre, praising how their eco-benefits help improve urban areas. Lets explore exactly what the green roof environmental benefits are.
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What Drainage Does A Green Roof Need
A green roof installation consists of a number of layers, and needs to follow some basic principles. Firstly, soils can potentially have a negative impact on the waterproofing layer. Therefore it is standard practice to have a protection layer on the surface of the roof this is essentially a puncture-resistant geotextile.
I often dispense with conventional drainage layer, and instead weave dry shingle river channels across the green roof to move excess rainwater to the outlet. This approach also has the added value of giving some pattern and topography to the finished green roof.
Dusty Gedges
Although green roofs store rainwater, there needs to be adequate drainage too to enable excess water to drain off the roof. The conventional approach is to use a plastic eggshell-style drainage layer, but there are natural alternatives. A gravel layer was traditionally used on the continent, but it is heavy and increases the load on the roof. I have recently seen a cockleshell layer being used on a number of small green roofs cockles make a lightweight alternative to gravel.
In order to stop the soils washing out, a filter sheet is installed above the drainage layer. This also needs to run up the sides of all perimeters. This later lets the water move through, but holds back the fine particles of soil.
What Grass Roof Systems Are Available
There are three basic types of green roof: intensive , extensive and semi-extensive .
Intensive systems consist of a thick layer of soil in which a variety of grasses, herbs, flowers and shrubs can grow. These need to be accessible gardens and can even be used as a recreation space. They provide a valuable habitat for wildlife but place significant weight on the building and need substantial roof support. They offer good insulation and better water absorption than the thin types, but need a lot of care.
Extensive green roofs are generally made up of a shallow layer of substrate planted with low-growing, stress-tolerant grasses, mosses and sedum. These lightweight systems require little maintenance. The insulation quality is relatively low and extensive systems always incorporate conventional insulation.
Semi-extensive systems have slightly greater depth than extensive systems but constructed on the same principles to allow for a greater diversity of plants. It is also relatively low-maintenance.
A meadow roof brings this single storey extension from to life, while also improving the space’s insulation.
Intensive systems and meadow roofs need to be designed in, as they are heavy and the supporting structure needs to be designed to carry the weight. Extensive and semi-extensive roofs are less of a problem. They offer less water retention and insulation, but are easier to install and maintain.
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Can You Grow Food On A Green Roof
Yes! They are excellent for growing food and are used extensively for this purpose in urban settings.
These unique roofs provide much-needed space for gardening a variety of delicious fruits and vegetables, and in some cases, even fruit trees!
Although, in theory, all green roofs can grow food, its best practice to try this intensive form of gardening on a flat roofed surface.
What Are The Four Main Benefits
Living roofs have many ecological and economic benefits, making them one of the most effective and impactful sustainability options available.
Lets take a look at the top four benefits.
Rainwater Buffering
When rainwater hits the roof, its vegetation absorbs and purifies the water before discharging the excess into the sewage system.
This process ensures cleaner water enters the sewer systems, reducing the load on the sewage purification system.
It also reduces the chance of flooding and helps stabilize groundwater levels.
Air Purification
Its no secrete that plants are powerful air purifiers by removing contaminates and CO2 from the atmosphere and converting them into clean oxygen.
Green roofs effectively help purify the air, reducing emissions and providing clean, fresh air.
Ambient Temperature Reduction
One relatively unknown specialty of plants is their ability to cool the surrounding area.
In fact, plants absorb a whopping 50% of sunlight and reflect another 30% drastically reducing the ambient temperature in the direct vicinity.
The result is a cooler internal building temperature which can lead to substantial air conditioning savings and an overall temperature reduction in the city of up to 3 degrees!
Increases The Roofs Life Span
Since a green roof offers protection against the elements, it can expand your conventional roofs lifespan to as much as forty years or longer!
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Who Can Design And Install Green Roofs And Walls
A Green Roof Professional should be the professional of choice on any green roof project, and many of our GRPs are also equipped to design and install green walls. Some jurisdictions specify that a GRP be part of any green roof design team.
Because green roof systems include materials not found on conventional roofs, we recommend that you choose a qualified roofing contractor with experience in green roof installation to install the non-living components . Contractors can be found in the Green Pages Industry Directory.
You can also contact a roofing consultant, who will assess your roofing design needs, ensure quality control and recommend a suitable green roof system.
Best Plants To Use On A Green Roof
Whats your local climate like? Which plants are readily available to you? Do you have an intensive, semi-intensive, or extensive green roof system?
All of these questions go a long way towards figuring out the best plants to use on a green roof, specifically, your green roof.
But lets have a look at some examples for an intensive/semi-intensive and extensive green roof system.
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Costs And Financial Benefits
A properly designed and installed extensive green-roof system can cost $108$248/m2 while an intensive green roof costs $355$2,368/m2 However, since most of the materials used to build the green roof can be salvaged, it is estimated that the cost of replacing a green roof is generally one third of the initial installation costs.
With the initial cost of installing a green roof in mind, there are many financial benefits that accompany green roofing.
What Are The Benefits Of A Green Roof
When it comes to roofing, green roofs are, without doubt, one of the more visible signals that you have built a sustainable home. There is a lot of cynicism that they dont actually serve enough eco purpose to be worthwhile, but they do have some genuine benefits:
- they absorb heat from the sun
- they absorb CO2
- they absorb a large proportion of the water that falls on them
- they provide a degree of insulation more cooling the building in summer as opposed to staying warm in winter
- critically, they replace the ecology that the building stands upon.
Green roofs also serve an aesthetic purpose, helping to soften the look of rooftops and blend buildings into the natural environment.
A green roof is, in ecological terms, a great and simple thing to do. It replaces the ecology the new house sits upon, thereby replacing the habitat that a house takes away. Used over a whole roof, a green roof will be the single overriding design influence on the house as well as impacting on the construction, right down to the foundations.
But green roofs do not necessarily need to be applied to the whole roof, or even the house itself. If the roof is accessible, having just a section planted is visually pleasing and a step in the right direction. Alternatively, install a green roof on an existing shed or garage, or install an extensive system on a flat-roofed extension.
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Finding Cool Roofing Products
Cool roof qualifications, such as minimum values of solar reflectance and thermal emittance, vary by standard or program, location, building type, and roof slope. Therefore, there is no single definition of a cool roof. However, the Rated Products Directory of the Cool Roof Rating Council reports the solar reflectance and thermal emittance of thousands of roofing products.
Green Roof Cost Benefit Analysis
The report includes the cost benefit analysis for green roofs as well, and offers data including:
- GSA green roof report estimated that green roofs on commercial and public buildings provide a payback, based on 50 year average annual savings, of about 6.2 years nationally, internal rate of return of 5.2%, and an ROI of 224%, based on a net present value of $2.7/square foot.
- Primary green roof costs are related to installation and maintenance.
- Primary economic benefits of installing green roofs are lower energy costs, less frequent roof replacement due to greater durability, reduced stormwater management costs, and creation of job opportunities.
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The Downsides Of Green Roofs
There can be some drawbacks to installing a green roof. These are mostly to do with the risks associated with poor construction and the cost of some green roofs. Its important to consider these potential issues before you install your own.
The biggest risk is around getting the installation wrong and causing damage to your property, including roof leaks, root penetration and even roof collapse. If you decide to install your own green roof, make sure you follow a clear construction plan. Our how to guide to green roof construction has everything you need to know about installing your own green roof but for complete confidence you should use a professional.
When it comes to price, its true that green roofs are an investment – theres no such thing as a cheap green roof although at Permagard we work hard to offer high quality at a reasonable price.
Youll need to take into consideration the cost of all elements of your green roof system. If you choose a contractor to build your green roof, youll also need to factor in this additional cost. While these upfront costs can seem expensive, remember that once installed, the ongoing maintenance costs are very little.
Moderation Of Urban Heat Island Effect
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Through the daily dew and evaporation cycle, plants on vertical and horizontal surfaces are able to cool cities during hot summer months and reduce the Urban Heat Island effect. The light absorbed by vegetation would otherwise be converted into heat energy.
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UHI is also mitigated by the covering some of the hottest surfaces in the urban environment – black rooftops.
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Green roofs can also help reduce the distribution of dust and particulate matter throughout the city, as well as the production of smog. This can play a role in reducing greenhouse gas emissions and adapting urban areas to a future climate with warmer summers.
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How Much Does A Green Roof Cost
The cost of a green roof varies considerably depending on the type and factors such as the depth of growing medium, selected plants, size of installation, use of irrigation, and whether they are to be accessible on inaccessible – intensive, semi-intensive, or extensive. Intensive green roofs typically require greater investment but confer the benefits of accessibility. An installed extensive green roof with root repellent/waterproof membranes may be installed for $10-$24 per square foot. While green roofs typically require a greater initial investment, it is important to keep in mind that they can extend the life of the roof membrane and reduce the heating and cooling costs of your building. Speak to a qualified Green Roof Professional about the range of costs and benefits for different green roof systems and designs.
Green Roof Installation Labor Cost
At $5 to $10 per square foot, green roof labor costs make up a significant portion of the installation price because its an intense and time-consuming job. For a 1,700-square-foot roof, you can expect to pay between $8,500 and $17,000 in labor alone. That price could go up if your roof has a steep pitch or complex design patterns.
Installation costs run higher if you need to replace your existing roof. Removing a roof costs between $1 to $5 per square foot.
Living roofs can work on flat or sloped roofs, though flat roofs are more common. Installing a flat roof costs between $3,200 and $9,000.
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What Is The Purpose Of A Green Roof
These roofs have many different purposes, benefiting both the homeowner and the environment.
They dramatically reduce electric costs by providing insulation, thermal mass, and shade to the building.
When it comes to the environment, green roofs provide a much-welcomed urban habitat for animals and plants, increasing local biodiversity.
What Can I Plant On A Green Roof
The best green roofs in the long term tend to be ones that a re planted and seeded. This approach allows the roof to develop and adapt to the particular circumstances on any given green roof.
There are now UK nurseries and seed companies that can supply plants for green roofs. Small plants should be used with plug balls of around 55mm. These small plugs have plants with a small leaf area, meaning theyre less susceptible to water stress and can respond better to the conditions on a green roof. Pre-grown solutions are another approach, whether sedum or wildflower blankets. For sedum blankets we would recommend at least 80mm substrate, and for wildflowers at least 150mm.
If you are going to plant a green roof, choose a wide selection of wildflowers and sedums:
- Non-native alpines and bulbs such as crocus and dwarf iris can be planted too.
- Many bulbous plants are adapted to suffer extreme cold and extreme heat.
- Muscari is a classic plant of the Turkish mountains theyre covered in snow throughout the winter and experience the Anatolian summers and as such, is a great option for green roofs.
- Another bulbous plant that is a must is chives, which are hardy and will stay in flower even in droughts.
- Autumn bulbs like cyclamen and Colchicum autumnal bring colour later in the year.
- Choose native wildflowers that benefit wildlife too, such as Vipers bugloss and birds foot trefoil.
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