6. The Big Green: Green Roofs vs Roof Gardens

According to Kenji Lopez (2009) from the The Phi Project, a green roof doesn't refers to painting the roofs green, or having plants in pots, but to a change into the use of technology for an ecological function to improve the habitat or to save in energy consumption. He defines it as a "a roof of a building that is partial or totally covered with vegetation, either directly on it or a cultivation medium", that serves an ecological function.

As you can see a green roof takes a lot more that putting a bunch of plants together. Involves the use of technology to redesign and improve the area where it will be placed, specially on creating a a suitable area for plants to grow on what used to be solid surface mad of concrete. That's why it's called a "change into the use of technology".

Green Roofs are very cool to look at, but they have way more benefits than just making a rooftop look good.  As you will see these have many uses than just the visual aspect.  Some uses and benefits are:

• Cultivate fruits, vegetables and flowers
• Improve building climate
• Prolong the roof's usable life
• Filter contaminants and heavy metals from rain water
• Reduce the risk of flooding
• Work as an acoustic barrier
• Protect biodiversity on urban areas
• Diminish the loos of heat from building during winters, reducing energy consumption.

According to the Chicago Specialty Gardens (2009) these two terms are often used interchangeably, but there are significant differences between green roofs and rooftop gardens. Even tough both are installed on top of buildings (which are structurally suited for such installation). and both utilize plants and  benefit the environment..    

So lets compare:

A green roof , like your lawn, is generally flat, thin (4-6” of soil) and planted with a family of short plants called sedum. Sedum is drought tolerant and can take extremes of heat and wind while protecting the roof membrane from the sun’s UV rays and providing environmental benefits like storm water management, ambient temperature stabilization, soundproofing, etc.

A rooftop garden , on the other hand, is like your backyard patio space – but on top of a roof. Almost anything you can put into a ground level patio can be installed on a rooftop. Large and small plants. Barbecue grills. Furniture. Lighting. Stone, wood, water features, spas, sound systems, even putting greens. Just about anything is possible.

To make it more simple I guess we can actually quote a statement on the Chicago Specialty Gardens web page:

  " the difference between a green roof and a rooftop garden is kind of like the difference between a turf lawn and a patio garden bed with trees and shrubs".      

:-)

What we meant with this title is that making a Green Roof is a difficult but mostly expensive , so we actually would need lots of money to do it.

First, they require a thickness of soil considerable to cultivate big plants and traditional grass which means preparing the area with layers of soil .

According to Green-buildings.com (2008), a member of the United States Green Building Council,  in the United States of America the cost for a green roof would range from $10 to $25 per square foot or $108 - $269 per square meter (one square meter = approximately 10.76 square feet). More sophisticated green roof (or green wall) installations can cost from $25 to $100 per square foot, or $269-$1075 per square meter or more.

On the next pictures you can see a common five layer preparation for a green roof, where the first membrane layer is commonly the most expensive one.

It's important to say that certain countries, states and cities have economic incentives to encourage the installation of green roofs.

As you can see it takes a lot of preparation and money to actually create a green roof. That will end up changing our initial approach to our project.  We finally came up with a solution. 

Want to find out what we did? 

Just keep going and you will see!!

After getting a clearer picture of the BIG difference between Green Roofs and Roof Gardens, we knew that we could not build Green Roofs at our school mainly because of our budget, which wasn't much at all.  So , we came out with a great approach that ended up being a more cost effective approach to solving our problem. 

Want to find out what we did and and how we did it?

Stick around and see how we came out with
"the  76 cents solution" !