A commercial building’s roof can be a perfect space for green roofing. If you are considering converting your building’s roof from standard to green, you need to know a few things. Let’s get started.
What Are the Benefits of Having a Green Roof?
A green roof offers certain benefits over a traditional flat roof:
- It helps reduce stormwater runoff. Instead of the rainwater pouring off the roof to the ground below, some of it gets absorbed by the soil and plantings.
- It improves energy efficiency. The plantings and their infrastructure offer a layer of insulation against the roof, making it easier to cool and heat the building below.
- It improves air quality. The plantings help convert carbon dioxide into oxygen. Some plants also help absorb other air-borne pollutants.
- It offers a habitat. Green grass, flowers, trees, and other plantings offer a place for birds, insects, and even small mammals to call home.
- It lasts longer than a traditional flat roof. A green roof can last two or even three times longer than a traditional flat roof installation.
- It offers extra gathering space. With the appropriate structures and access, the green roof can be a gathering and socialization spot for the building’s occupants and guests.
Are There Different Kinds of Green Roofs?
Green roofs are usually categorized by the depth of the soil and the types of plants involved.
An extensive green roof has a shallower level of soil with drought-resistant plants which can exist without deep depths of soil. The extensive type is lighter because of its shallower depths.
An intensive green roof uses deeper levels of soil to hold more varieties of plantings. Roofs which look like a park with grass and trees are the intensive type. This type of green roof is heavier than extensive green roofs and may require additional support.
Some green roofs combine extensive and intensive roof elements. There may be extensive areas which include grass and smaller plants. Then mixed in are a few larger intensive areas containing small trees or bushes.
What Goes Into Making a Green Roof?
Green roofs can be installed on just about any roof. However, they are most common on roofs with a pitch of 3:12 or less. That is a three foot of rise for every 12 feet of roof.
Installing a green roof on a flat or shallow sloped roof is fairly straightforward. It involves laying down multiple barriers between the roof and planting medium. This prevents rot and roots from reaching the roof deck.
The next steps go something like this:
- Install a waterproof membrane.
- Lay down a plastic sheet to prevent root penetration.
- Layer on foam insulation to increase R-value
- Place a drainage mat.
- Frame the sides to prevent soil loss.
- Add soil and plants.
- Use water to settle the soil and to provide water to the plants.
Another option is to set trays down on top of the waterproof barriers.
What Is Involved with Green Roof Maintenance?
In the first year, it’s important to check the plants every couple of weeks to ensure they are properly rooting and not experiencing too much stress. After the first year, monthly or quarterly inspections are usually enough.
Ongoing maintenance involves a number of activities:
- Controlling weeds
- Monitoring moisture levels
- Fertilizing the soil
- Deadheading plants
- Removing debris
- Controlling insects
Many roofs require irrigation systems to maintain adequate moisture during drier seasons. Irrigation can involve hand watering, drip installations, or overhead spray. Drip is preferred in most applications as it conserves water and does not require manual intervention.
The types of plantings and the design of the roof can affect maintenance needs. A manicured public space filled with grass and other higher-maintenance plantings will require more attention than a roof planted with drought-resistant native plants that require no trimming.
Is a Green Roof Worth the Investment?
The main drawback of a green roof is it can be double or triple the price of installing a traditional flat roof. If you are retrofitting a green roof, you need to consider whether the structure can support the additional weight. It may mean you have to add additional support before installing the green roof. Some green roofs do require extra maintenance.
Is it worth the investment? A green roof, properly installed, can last twice as long as a standard flat roof. It also helps enhance the energy efficiency of the building, offers extra space for humans and nature, and improves air quality in the area.
You have to decide if the extra costs involved are worth the benefits a green roof offers. If you are interested in learning more about a green roof, contact A-1 Property Services. We offer full design and installation services for your green roofing needs.