What is a Living Roof?
A living roof is one that is partially or fully covered with living greenery, whether it is flowers, herbs, vegetables, shrubs, or other plant growth.
What are the Benefits of a Living Roof?
There are several benefits of a living roof, including:
- Energy savings. Living roofs provide excellent insulation. They can make the surface of your roof 30 to 40% cooler. They can also help your home retain heat on the inside during cold weather.
- Sound insulation. A living or green roof can provide surprisingly effective environmental sound absorption.
- They can reduce water runoff from a roof by more than 60%. That retention of rainwater can help prevent localized flooding. After months of drought like we’ve experienced in the Bay Area, the recent heavy rains often cause water to pool around buildings with inadequate drainage.
- Longevity. A living roof can last around 40 years.
Where Can You Find Examples of a Living Roof?
You can find them on commercial and residential buildings. San Francisco’s Academy of Sciences has a living roof that covers 87% of its 2.5-acre rooftop. It is a wonderful example of a roof that helps regulate the interior temperature of the building while providing a habitat for a wide variety of plants and animals.
San Francisco includes at least two other commercial buildings with green roofs. The California Pacific Medical Center redesigned their hospital in 2019 with a number of environmentally friendly options, including five green roofs.
You will also find a garden as the central element of the living green roof at STEM Kitchen and Garden in Mission Bay. They use the roof space to grow seasonal fruits, herbs and vegetables which they feature in their restaurant offerings. It is a great place to enjoy the rooftop view, while sipping a drink.
The San Francisco Planning Department’s Resilience and Sustainability plan includes a Climate Resilience section recognizing the value of putting San Francisco rooftops to productive use. Chances are the city may become a great center for green roofs.
Effective January 1st, 2017, San Francisco became the first U.S. city to mandate solar and living roofs on most new construction. With the passage of this legislation, between 15% and 30% of roof space on most new construction projects will incorporate solar, living roofs, or a combination of both (San Francisco Planning).
If you are interested in seeing living roofs on residential buildings, a drive up the coast to Sea Ranch will provide you with several examples. Some people are looking at them anew, exploring their use as an alternative to conventional roofs when it comes to fire prevention.
What Kind of Climate is Right to Have a Healthy Living Roof?
A living roof will differ from one climate to another. It isn’t like installing a conventional roof. Rainfall and temperature changes will impact your choice of materials and the plants you choose.
A living roof is heavier than the average roof, so you’ll need to know if your home’s structure will support the added weight.
What Types of Materials Will You Find on a Living Roof?
Just as the kind of living or green roof you choose will be impacted by the climate your home is located in, the material will differ according to the type of green roof you choose.
Other factors that impact the materials needed will be the building codes for your locale. There are two kinds of living roofs. One is extensive (soil layer of 6 inches or less) and the other is intensive (soil layer of more than 6 inches). Also, green roofs are better suited to flat, rather than sloped roofs.
The basic structure is as follows:
- Waterproof membrane. The first layer is a monolithic type of waterproof membrane (rubber or plastic) on top of the roof decking.
- Plastic sheeting that acts as a way to isolate the roots of what is to be planted comes next.
- A layer of insulation is next.
- Then, you’ll want a system for drainage.
- Filter fabric or geotextiles function as a way to allow water to pass through the layer while keeping the soil itself from migrating through the fabric.
- Next comes the layer of soil.
- The final layer is the plants themselves.
- In most climates, irrigation is also a consideration.
Who Might be a Candidate for Having a Living Roof Installed on their Home?
A living roof is a considerable investment. The benefits already listed, like energy savings, sound insulation and longevity make it a good investment for homeowners who are willing to put in the extra maintenance.
In Marin, Sonoma and Napa County drought resistant plants that favor less water are best. Homes with flat roofs work best, but accommodations can be made for roofs with slight slopes.
Is There a Type of Home That Should Not Have a Living Roof installed?
Homes with steeply sloped roofs are not a good design for a living roof. Another consideration is where you live and what type of mini-climate your home is located within.
What is Required to Have a Living Roof Installed?
Permits are required for reroofing projects and living or green roofs are no exception. The requirements may vary from region to region, so you’ll want to check with your municipality’s building department before moving forward with a project.
Due to the added weight and more intricate design of a living roof, it is a good idea to work with a professional who has experience with living roofs. You may also want to work closely with a local plant nursery to get advice on the plants that will work best in shallower soil and are suited to your particular climate.
If you are considering a new roof and would like to get an estimate or want to explore roofing materials in more detail, contact us today. One of our experienced professionals would be happy to help you.