APEX GREEN ROOFS: FREQUENTLY ASKED QUESTIONS
What is a green roof?
Green roofs (otherwise known as vegetated or vegetative roofs, ecoroofs, or living roofs) consist of a vegetated roof covering which is planted over an existing roof structure. The plant medium and soil is placed over a protective waterproof membrane and a drainage layer system. A green roof can completely or partially cover a roof's surface and still be considered a "green roof" Sometimes, but not always, green roofs are combined with rooftop container gardens. Green roofs absorb water, create a living habitat, provide insulation, and help clean the air. Read all benefits of green roofing here...
How do I get started if I want a green roof installed on my building?
EXISTING COMMERCIAL & RESIDENTIAL BUILDINGS:
First and foremost, determine how much weight the existing roof can support (otherwise known as the total "dead load"). It is also important to know the exact pitch of your roof, if applicable. This information can usually be found in architectural drawings or blue prints. If you do not have these documents for your building, then we recommend that you hire a structural engineer to assist you. We may be able to help recommend a reputable structural engineer in your area should you need one. You will also need to know what type of waterproofing system exists on your roof, or what type of waterproofing method you may have plans to install. If you are not sure what type of waterproofing system you have, it is likely that we can assist you in determining this. Knowing the total dead load, pitch, and waterproofing method of an existing roof structure allows Apex Green Roofs to determine the best options for design and construction of a green roof system. Once you know these variables, please contact us.
NEW COMMERCIAL & RESIDENTIAL BUILDINGS:
Blueprints and architectural drawings will have the information Apex Green Roofs needs in order to determine the best green roof installation system for your roof plan. We can both design and build your green roof system, as well as work with your architect to best meet your goals. If you are in interested in involving Apex Green Roofs in your project, and/or you would like to review our green roof specifications, please contact us.
How much does a green roof cost?
The cost of a green roof can vary depending on the conditions of the roof, the total surface area, and the type of green roof system to be installed. As a general guide, an extensive system can range from $8-$15 per square foot, a semi-intensive system can range from $15-$25 per square foot, and a intensive system can cost $25+ depending on the ultimate depth of the installation, plant varieties, aesthetic goals, etc.
While the installation of a green roof requires a larger initial investment up front than a typical non-vegetated roof, a green roof will last 3-4 times longer than a typical roof (an estimated 60-80 years). This is because the plant membrane protects the surface of the roof membrane from exposure to UV rays and weather conditions (primarily rain and ice). Sun and rain break down the surface of the roof much more rapidly when the surface is exposed.
In addition, green roofs can reduce your heating and cooling energy costs up to 30%. The best energy savings tend to occur on the largest buildings, but even small residential buildings will see some energy savings.
In some cities and towns, grants and subsidies exist which can help fund the installation of a green roof. Tax incentives for installing a green roof exist in some parts of the country as well. Check with your local government to see if this is an option for you.
What are the structural requirements of my building in order to have a green roof installed successfully?
As a general rule of thumb, the saturated contents of our lightest green roof system weigh 7lbs per square foot per inch thickness. Therefore, your roof must be able to support at least this much weight.
Do I need irrigation on my green roof?
We feel that irrigation defeats the purpose of a green roof (to absorb storm water) and we do not recommend it for our extensive system installations which are composed primarily of sedums species. However, non-sedums, or herbaceous plants, may sometimes require irrigation depending on the plant material. Therefore, irrigation systems may be a necessity with certain semi-intensive and intensive systems which can be deep enough to support herbaceous plant varieties.
Are native or non-native species grown on a green roof?
A green roof is not a native environment due to the amount of heat, exposure to the sun, wind, and rain the plant systems must endure in order to survive in such a habitat. Sedums are native to coastal, alpine, and desert climates and are therefore more adapted to changing weather conditions which can be harsh at times. They are ground covering plants by nature and do very well in a green roof environment. Herbaceous native plants tend to require irrigation to survive. In some installations, native species can thrive if given the correct conditions and proper care.
Can a pitched roof support a green roof system?
Yes - a green roof can be installed on almost any roof pitch, however the price of the green roof system will increase with the pitch of the roof simply because more materials are needed in order to support the vegetation, and these roofs may require more initial maintenance while the plants establish themselves. The maximum pitch for a roof without the use of slope retention materials is 2:12.
What is the difference between green roof module systems, and built-in-place green roof installations?
Module systems are essentially green roof plants grown in moveable trays or crates, while an extensive or intensive system is built onto the surface of the roof. See the table below for a detailed comparison of tray systems vs built-in-place systems summarizing their benefits, costs, and installation requirements. Download this table
|Topic||Tray Systems||Built-In-Place Systems|
|Lead Time||Minimum of 3 months (plants are pre-grown in nurseries)||2 week lead time (typical extensive systems are planted with cuttings or plugs)|
|Maintenance||Can be initially less maintenance than built-in-place systems. Coverage will decline after installation as conditions are less ideal than in a nursery environment.||Initially more maintenance when established with plugs and cuttings, though similar when established with pre-vegetated mats.|
|Cost for typical 4” extensive system||$13-20 per sq ft tray||$9-$15 per sq ft (which includes 8 maintenance visits $13-20 per sq ft tray over 2 years)|
|Waterproofing||Covering all areas of the waterproofing material can be more challenging, depending on the dimensions of a roof. In many cases, gaps expose areas of the membrane to the sun/weather which will shorten the life of the roof.||Built-in-place systems cover the entire surface of the waterproofing membrane, therefore preserving it and extending the life of the roof.|
|Design||Less design flexibility (ex: curves, irregular angles, pitches)||Complete design flexibility|
|Leak Detection||Same requirements||Same requirements|
|Retro-Fit Roofs||Plastic (non-biodegradable) tray systems are good for those who wish to have a green roof and will be retro-fitting existing roofs with older waterproofing membranes. Trays have the ability to be moved more easily than a built-in-place system. They are also convenient for DIY homeowners looking to build their own residential green roof system.||Ideally, a built-in-place system would last 40+ years by protecting the waterproofing membrane from UV and temperature fluctuations. We typically recommend this type of installation on a waterproofing membrane that is less than 3 years old to maximize the life of the roof.|
|Aesthetics||Trays almost always visible, edges do not conform to curved edges or sharp angles.||Continuous vegetation; edges of the roof are continuous, limitless design options with curved spaces, angles, and pitch.|
|Plant Health||Depending on the type of tray plant health can be compromised as plants cannot share the resources of water and nutrients as easily.||Time proven complete eco-systems where plants adapt to the microclimate conditions of the roof surface.|
|Product Quality||Many manufacturers will not warranty anything but the module and soil. Modules ex poised to the sun on the edges are typically not warranteed.||40-70 years experience in Europe and USA. Fully warranteed plants and components as well as single source options.|
|Pitched Roofs||Not recommended – tray systems are likely to lose their shape or break apart on pitched roofs.||Can be installed on almost any pitch|
What happens if I have a leak on my roof?
EFVM (Electric Field Vector Mapping) testing is one method of testing we use in order to find the source of the leak quickly and efficiently. In this method of leak detection, an electric current triangulates where the leak is to within a foot of the source of the leak. As part of your warranty with Apex Green Roofs, if you have a leak, we will conduct EFVM testing in order to find the source and we will then patch your roof membrane and repair any damage to the living roof system that may have occurred due to the required repair work. Some roof systems are not EFVM compatible, and therefore require a more manual leak detection process. Therefore, warranties for non-EFVM compatible roofs can be slightly more expensive than those which are EFVM compatible.
What type of waterproofing should I have on my roof surface before installing a green roof system?
We recommend waterproofing systems that are compatible with EFVM (Electric Field Vector Mapping) testing, including TPO, PVC, and liquid plastics. Some roof systems like EPDM, are not compatible with Electric Field Vector Mapping, and asphalt can be easily eaten away by plant roots. A green roof system can still be installed on non-EFVM compatible roofs, however, certain precautions may need to be taken to either add a protective surface (root barrier) to the roof membrane before installation, or the overall warranty cost may need to be increased to cover the manual leak detection process on non-EFVM compatible roofs.
What kind of warranty plan can I have for my green roof?
Apex Green Roofs offers a full 10 year warranty on plant materials and green roof components. Should a leak exists at any point, we will help source and repair the leak using EFVM (Electric Field Vector Mapping). Roofs that are not EFVM compatible can still be covered by warranty, however, this warranty may cost more due to the manual leak detection process certain roofs may require.
In addition, we include 2 years of maintenance with all of our contracts. While a green roof is generally very low maintenance, it is important to check that the plants are establishing themselves well, and much of this process occurs within the first two years.
How are municipalities encouraging green roofs?
• Up to $5K per towards installation
• Fast-track permitting
• Density bonus
• Waived fees
• Required if developer receiving city assistance
New York, NY
• Tax credit of $4.50/sq ft up to $100K, beginning in January 2009
• Stormwater fees funding $500K available to FY09 projects
• Fast-track permitting
• Density bonus
• Up to 35% discount on stormwater charge
• Required if developer receiving city funds
• $50/sq meter grant (~$4.70/sq ft)
• Up to $10K for single family homes and $100K for other property owners