Green Rooftops are a great addition to any residential or commercial building for several reasons:

• Provides natural insulation
• Provides sound insulation
• Reduces utility bills
• Visually appealing
• Reduces water runoff
• Prolongs roof life span
• Reduces Urban Heat Island effect
• Increased green area for converting CO2 into Oxygen

What are Green Roofs?

Green Rooftops are roofs that are prepared for sustaining plant life on them. They usually involve a layer of soil with growing grass, turfgrass, shrubery, and sometimes even trees. In some cases, the layer of soil is replaced by other man-made material that allows vegetation to grow on it. There are two types of Green Roofs:

• Extensive Green Roofs
  These are lighter, cheaper green roofs which usually require little maintenance. They're made of only 2.5 to 6 inches of soil or other growing material, usually don't need extra irrigation beyond rain, and will only require normal maintenace of any roof (for example, clearing of roof drains). Also, due to the shallowness of the soil, these types of green roofs don't usually require any structural changes.
   
• Intensive Green Roofs
  These are heavy duty green roofs, usually called "Roof Gardens" which do require regular maintenance and irrigation. The soil depth starts at 8 inches and can support medium to larger plants, even trees. Due to the heavy load on the roof's structure, roof gardens usually require a roof structure with sustaining high load-bearing capacity.

Improved Insulation

Environment Canada found in a study that a 1-story building with a green roof of around 4 inches of soil and grass would require 25% less cooling in the summer. Another study found that 6 inches of soil and grass reduced transfer of heat from the outside by 95%, as well as reduced loss of heat to the outside by 26% when compared to a regular roof. Another study has shown that having a green rooftop can reduce inside temperature by 20 degrees Fahrenheit during the summer months.
All in all, studies are pointing to the fact that installing a green roof greatly reduces heating and cooling needs as it minimizes heat exchange with the outside.

But the advantages of having a green roof don't stop at thermal insulation: green roofs also offer improved sound insulation. Soil actually reduces lower frequency sounds, while the vegetation traps higher frequencies. Overall, studies have shown that green roofs may reduce sounds by 50 decibels.

Preventing Water Runoff

When rain hits the ground it is normally absorved by soil, plants, and other organic material in its way into underground water tables. In heavily populated areas green spaces are replaced by buildings, sidewalks, and roads which bounce off rainwater instead of allowing it to seep through the ground. And so the excess water washed off roads and buildings collects oil, chemicals, animal waste, and many other impurities and bacteria before finding its way into storm drains, which in turn drains without any water treatment directly into rivers and other waterways.

Water runoff is a huge problem for any city, especially those with flash-flooding problems. Maximizing the presence of green rooftops means that some of this rainwater will be kept in the area and any impurities it carries will be broken down locally, instead of concentrating in waterways. Studies have estimated the water runoff mitigation of a green roof to be an average of 70%.

Urban Heat Island Effect

Heavily populated areas are usually 2 to 10 degrees hotter than surrounding areas, a fact so generally accepted that weather reports often differentiate between downtown and suburban temperatures. One of the major factors of UHI is the heavy presence of asphalt in roads, concrete in sidewalks and buildings and tar on rooftops, all of which are great for collecting heat from the sun.

Because of the thermal properties of these material, heat from the sun is collected during the day and radiated at night, which can be appreciated especially at night during summer and throughout winter, and can even have an impact on rainfall. To put it in numbers, in a study made by Austech Roof Consultants in a 91 degree day, the temperature of a black tar roof reached 154 degrees. The green roof's soil oscillated between 88 and 100 degrees.

Extended Roof Life

Having a green rooftop prolongs the lifetime of your roof as it prevents extreme temperature changes, which often result in the contraction and expansion of the roof materials, causing the weakening thereof. Due to this protection from the elements, a roof's life span could be doubled, which translates into savings well into the thousands of dollars.

Aesthetic Appeal

It is a common known setback that living in extensive metropolitan areas normally means restricted access to green spaces and the tranquility and sense of freedom they offer. Apartment buildings with accessible green rooftops are therefore especially attractive to tenants as they provide access to a green space, a place to walk their pets, and a greater sense of privacy and safety absent from public parks.

In addition to being attractive to its own tenants, neighboring buildings overlooking these green spaces also profit through the aesthetic appeal of their neighbor's green rooftop, raising property value.