By Rebecca Naughtin
Green roofs have become more and more achievable over the past few years, with numerous products coming onto the market and a greater understanding of green roof construction and benefits. Here is an introductory guide to what the advantages are, whether a green roof would suit your house, and how you can go about getting one.
Why build a green roof?
Green roofs provide a variety of benefits to you and your home, from reducing energy costs through to effective insulation, filtration of air (depending on the species of plants you choose) and, of course, aesthetic beauty. There are also benefits that help on a larger scale, such as reduction of the urban heat island effect, retention and reduction of stormwater run-off into our oceans, and increasing the natural habitat of fauna within urban environments. All of these benefits add up to creating a better living environment that can also increase the value of your property.
Would a green roof suit my house?
This is an important question, the answer to which will be dependent on whether you want to retrofit a green roof to your existing home or include in a new-build design.
Important factors to consider are:
How big will the green roof be? Will the roof be sloped? Will it require a lot of substrate or will it be shallow? What kind of structure underlies your existing roof? How will it drain? How will it be watered? Answering these questions will begin to determine whether a green roof is suitable for your home. I would also recommend engaging a professional with knowledge in green roofs before beginning any works.
I've decided to build a green roof. How do I do it?
You will need to plan if you want a green roof that can be walked on, as this is an "intensive" green roof that requires more substrate, more structure and will cost more money. On the other hand, if you want a green roof that will not be traversed, you can build an "extensive" green roof that will be lighter, require less substrate and be more economical.
Both will require an engineer to determine whether your existing or proposed roof structure will be suitable. Remember, you aren't just accounting for the weight of the soil and plants but for the weight of absorbed water from heavy rains and the like.
Which professionals do I need?
You will need to engage an engineer to determine your roof's load-bearing capacity for dead loads, live loads and transient loads. You can then either engage professionals who solely deal in green roofs, or you may engage an architect who has knowledge of green roofs and their design. If you do engage an architect or designer, ensure they have experience with plant species selections, or engage an additional professional such as a horticulturist. This will be one of the key aspects to the success and beauty of your design (not to mention hopefully resulting in a sustainable garden that does not
require huge quantities of water).
Are there ready-made products I can use?
Some professionals may have product recommendations specific to your project, such as modular systems that are easy to install, maintain and remove if need be. These can be economical and hassle free, though can place some limits on the design and whether it will be sturdy enough to walk on.
Are there any site-specific factors to consider?
Within the design and planning phase for your green roof, you will need to consider choosing the species of plants for your specific space. Some aspects to consider include: wind, rainfall (amount and duration), sun exposure, environment temperature and fluctuations, and personal aesthetic choices. There are many guides on what species are recommended for green roofs, though again it's best to consult a professional who has worked in your area.
What elements make up a green roof?
Your green roof will be made up of multiple layers, including but not limited to: a layer of vegetation, growing substrate, filter sheet, drainage layer, protection mat, root barrier, and waterproofing. It is important to note that different types of green roofs have different constructions and needs, as well as the fact that there are varying products on the market. Always consult a professional.
How will I maintain my green roof?
You will need to plan how you will maintain your green roof, check for any potential leaks, plan how often plants may need to be pruned, and calculate how much irrigation is required, if any. You will also need to have planned whether access to the roof is possible and, if so, how to best go about it in a safe manner. Also, be sure to monitor your plant growth to ensure plants are healthy and, if not, determine why.
Whichever green roof you build – no matter how small or large – ensure you consult professionals to reduce risk of leakage, structural problems and plant health problems.
Enjoy your new beautiful green roof!