How Does a Green Roof Work?

Green Roofing View From top

Commercial Green Roofing

A green roof also referred to as a living roof, is where the roof of a structure has a garden growing over a waterproof membrane. It has become common in large cities on high-rise apartment buildings so that residents can get fresh vegetables or enjoy blooming flowers. A green roof may have a root barrier with a drainage and irrigation system in place.

Today, more businesses are taking an initiative to be more proactive in our environment and have seen the green roof benefits are many. Building owners are seeing green eco roofing to be more than a trend and are reaching out to find more green roofing solutions they can implement.

We are going to answer some common questions about this trend, and hopefully, we will provide you more information that will help you make an educated decision on installing a green roof on your building.  

Why are green roofs eco friendly?

A green roof aka a living roof has gained popularity because there are so many benefits to having one. The first thing about them we can benefit from immediately – they are pretty to look at! But other than the simple beauty aspect, they are eco-friendly with these 4 facts supporting that claim:

  • A black tar roof is the traditional roof, which attracts heat. A green roof absorbs heat and provides the building with a layer of natural insulation. With a green roof of 6” deep, a building can see up to 75% reduction of energy during the summer because the air conditioning isn’t working as hard.  With less demand from the air conditioning, air pollution is decreased and so are greenhouse gas emissions.
  • In urban settings, heat is absorbed and gets trapped. A green roof can reduce the condition referred to as Urban Heat Island Effect, which is the absorption and trapping of heat.
  • The plants on a green roof removes air particulates and produces oxygen as well as provide a natural shade for the building. Because of that natural shade, experts have determined that the lifespan of the roof is two times as long as the traditional black tar rooftops.
  • A green roof will reduce storm water runoff by absorbing the water, slowing it down in urban settings where the surfaces are hard, giving the runoff no place to go except in the sewer system that is often overworked already. Even in the summer months, 90% of the precipitation is collected by a green roof and up to 40% in the winter.

Do green roofs provide insulation?

There are various types of green roofs to choose from, and the level of insulation will be affected by many factors. The moisture level will decide on the effectiveness of its insulation factor, and that can vary from climate to climate. As such, there is no U-Value given for a green roof, but normally, the deeper the layers, the better the insulation. A consideration that should not be forgotten when installing a green roof is the weight of it will put additional strain on the structure.

How do you maintain a green roof?

There isn’t any simple answer to this question. Like any garden, a green roof will require some level of maintenance, and the more involved the green roof, the more involved the maintenance. Some basic general tips for maintaining a green roof are:

  • Weed and remove the unwanted: With soil, you get weeds and it is important to remove those weeds so that your plants can take hold.
  • Route all drainage away:   Keep the plants away from the border and roof edge as well as the gravel areas, drain outlets, and any other areas of roof penetrations. Plants can clog drains and cause big problems.  
  • Add compost: Twice a year, autumn and spring, add nutrient-rich compost. This feeds the plants and replenishes the soil.
  • Weed and remove the unwanted: Yes, with birds and wind dropping seeds onto your green roof and before you know it, there is a might oak, or some other tree, sprouting in the middle of your garden.  Chances are your roof wouldn’t be able to support a tree’s weight, so once a month, do a walk-through and pull up any unwanted growths.
  • Water sparingly: A green roof should not be watered as often as a typical garden because of the additional weight it can put on the roof.
  • Watch for diseases and pests:  Watch for diseases and pests that may take to your green roof. A green roof is meant to increase biodiversity, which means it will attract insects, sometimes unwanted insects and pests, which could bring about diseases.
  • Keep a detailed maintenance diary:  This will help you with scheduling checkups and what was found each time. You can also make notes as to what does well in your green roof garden and what doesn’t do so well.

Are green roofs expensive?

With concerns of global warming and our natural resources dwindling, coupled with the cost of utilities increasing, having a green roof has gained in popularity for both businesses and residential structures.

When the cost of a conventional roof as compared to a green roof, the cost for installing a green roof was more than the conventional roof, but the ROI was double or more than the cost over the lifetime of the green roof. Almost 2/3 of the savings recognized came from reduction of required energy to cool and heat the building.  

When it comes to the expense of maintaining a green roof, it is important to plant what is natural to the region. This will save the need for irrigation as well as having to replace plants that don’t survive the climate of the region.

Flat Roof With Eco Friendly

What is the difference between green roofs intensive vs extensive types?

An intensive green roof is common among commercial structures and incorporates various plant sizes and types to create a large green area. There will be grass and ground cover, as well as flowers, shrubs, and some trees with walkways where people can enjoy and interact with nature. Some will add benches and tables, planter boxes and ponds, even water features to create a relaxing area.

An extensive roof is common among residential structures, both single-family and multi-family, primarily for the maintenance benefit they provide and where walking on the roof is less likely. They are also found on the outbuildings such as garages and sheds. This type of green roof is considered a low profile with high performance so that the additional weight on the roof is minimal.

How long does a green roof last?

Having a green roof isn’t all that new, but the popularity has picked up again as we have already discussed here. While the roof membrane must be protected and the weight-bearing of the structure must be considered before installing a green roof, they can expand the lifespan of a roof. When we look at green roofs in Europe from the 1960s, you will see they can last anywhere from 30 years and for as long as 50 years.

Overall – A Green Roof Is Worth The Commitment

The details and facts that we have presented here are proof that a green roof can be a commitment of money and time, but it also shows that there are many benefits to having one too. Take the time to do your own research, starting with verifying the strength of your roof top for the additional weight and what native plants will provide the best results. Call 513-342-8544 today for green roof installation in Cincinnati, OH.