With changes to both building codes and the public’s attitude to environmental issues, making old and new buildings more sustainable has never been more relevant. Though they’re still a bit of a niche in Australia, more green roofs are appearing on new homes every year and this trend is continually rising. But what is a green roof house design and how exactly do they work? Let’s take a closer look at green roof house designs.
What is a green roof house design?
A green roof incorporates a natural, growing medium and vegetation into the roof design. The growing medium can be either soil or a growing mat, while the vegetation can be any plant. A green roof can include a roof garden, and grass, and can be partially or completely covered in vegetation. There is also the option for green walls, also known as vertical gardens. The living vegetation creates a very unique look for your roof surface.
The idea of green roofs can date back to various ancient civilisations, including the Vikings who would lay turf on their structures and call it ‘sod roofs’, and its current popularity can be attributed to its sustainability factor. Though quite common across Europe, green roofs are less common in Australia, though they’re starting to see a rise in popularity.
An essential part of most green roofs and walls is a waterproof membrane between the soil and the house itself. Other features that are incorporated into a green roof layout usually add to the design’s sustainability, for example, solar panels or a watering system.
Structural capability
Usually, modern green roofs tend to be flat roof designs, however, any roof structure, including curved or sloping, could potentially have a green element to it. The essential thing is that you’ll need a structure that can withstand the extra weight that comes with a roof garden. With a green roof potentially weighing 180-500kgs per square metre, you’ll require a stronger physical roof structure to ensure everything is safe.
How much does a green roof house cost?
There’s no getting around that a green roof house is likely going to cost you more than a traditional roof. The reason for this is there are a lot more factors in designing and constructing a green roof than there are with a conventional roof. You also need to be aware that there are limited short-term financial returns with green roofs and they do require maintenance. If your interest in sustainability is purely to save money, a green roof may not be the best option for you.
The price of a green roof is hard to estimate because they can vary so much in scope and design. Just like regular gardens, roof gardens have a wide range of possibilities, so many that’s impossible to account for them all in this article. However, some factors that will influence the price of any roof include:
- Size of the project
- The complexity of the design (a green roof or green wall is going to be more complicated than average).
- The builder you hire
- Location, both in terms of how far your contractor needs to travel and the difficulties of the location itself.
- Materials used for the build.
- For green roofs, the plants you choose and how many.
What are the advantages of building a green roof house?
With some countries making a strong push for more homes to have green roofs, there are obviously some advantages to this design. Let’s take a look at some of the top reasons you should consider a green roof for your home.
Eco-friendly and sustainable
The main reason choose to go with a green roof is for the eco-friendly and sustainability. Plant life increases bio-diversity which has a range of benefits including improving air quality, providing homes for
We highly recommend talking to a landscape architect or someone who understands plants before planting anything on your roof garden. The last thing you want is for a plant to have a larger root system than your garden can handle.
Boosts Thermal Performance
A well-designed and installed green roof can substantially reduce the heating and cooling requirements of your home. This in turn means lower air conditioning and energy bills, and who doesn’t like the sound of that? In the city, temperatures tend to be higher and therefore a green roof could create an urban heat island effect which will help cool your home.
Though a green roof does provides significant thermal insulation, it’s currently difficult to get accredited insulation values for green roof construction in the Australian Building Industry. Therefore, to ensure your house meets the requirements of the National Building Code, you may have to install more traditional insulation methods, regardless of how effective your green roof is.
Can increase your roof’s lifespan and durability
Green roofs need to be designed for longevity, lasting upwards of fifty years. The extra structural integrity will increase your home’s durability, plus the soil will help your building’s pest and fire resistance.
Improved drainage
Moisture can cause all sorts of issues when it gets into your building structure, so decent drainage systems. Your green roof will absorb water, plus a substrate and sedum drainage layer will help deal with any extra water. Moisture issues can be incredibly destructive to your home, causing mould, mildew and even structural damage to your home. Therefore, quality drainage is a must, especially in rainy areas.
Better Sound Insulation
If your building is in a noisy area, like an urban space, busy neighbourhood or near a road, soil and vegetation will provide a natural sound insulation for your new home. These acoustic insulation benefits
What are the disadvantages of building a green roof house?
No design is perfect for everyone and green roofs are no exception. Here are a few things to consider before going ahead with a green roof on your home.
More expensive than traditional roofs
Green roof construction, design and maintenance are all going to cost more than a traditional roof, regardless of whether you’re building from scratch or adaption existing buildings. There are many reasons for this including the more intricate design, the additional materials, the plants you need to buy and then keep alive, the soil you’ll need, etc.
More Maintenance
All that vegetation requires upkeep to keep your home looking its best. One way to reduce maintenance is to use native plants from your area. A native plant will have evolved to survive and thrive in your area, whereas an exported plant will require you to put in more effort to mimic its natural habitat.
Increased Weight Load
With all that soil and vegetation comes a lot of extra weight and you need to be 100% your roof design can handle this. For such a unique project, you will need a building designer or architect to help create a safe and functional roof structure. This is especially true in Australia where there aren’t as many green roofs as in other countries.
May have issues with resale
Due to how few green roofs are on the Australian property market, it is a little difficult to determine what their resale value is like. Potentially, you could be ahead of the curb, especially if green roofs become more common and mainstream over the next few decades. Every house purchase is a gamble, but at the moment, green roofs are less tested on the market and currently are seen as a niche, acquired taste.
What are the most popular green roof house designs?
No two green roofs are quite the same, however, they can usually be divided into one of the following categories.
Extensive green roofs
An extensive green roof has a thin soil profile and is best suited for a roof with a sturdy foundation. These designs don’t lend themselves to general access (in other words, you won’t be able to have lots of people on your roof). Because of this somewhat thin soil profile, any plants should have shallow root systems to avoid any structural damage to your home. This would be the go-to choice for people looking to turn existing roofs into green roofs, though you’ll need to consult an expert about whether this is doable.
- Less maintenance
- Can be installed on some existing buildings.
- for a green roof, these are the most economical designs.
- Less thermal and sound insulation benefits, but still some.
Intensive green roofs
An intensive green roof has deeper soil or substrates which allows you to grow larger plants or in some cases, even trees. Intensive green roofs need to be designed as part of the building from the beginning, as the structure will need to have the inbuilt capacity to handle what you’re asking of it. Unlike extensive roofs, intensive green roofs can be accessed by people. They also require frequent maintenance and upkeep. Some other characteristics include:
- Tend to be the most expensive green roof option due to structural requirements.
- Soil planted can range from 200m to 1m+ deep.
- Increased thermal and sound insulation benefits.
Green walls
Green walls, sometimes called living walls, are a similar concept to green roofs… except it’s on the wall. Some of the most common types of green walls include:
- Green facades – pots or vines on the wall
- Living walls – more similar to green roofs, living walls involve a growing medium such as mats or vessels supported by a framework to grow lightweight plants.
- Passive – these are plants that happen to grow on the wall but don’t require a growing medium.
Green Roofs vs the Competition
Most of the below designs could potentially be green roofs.
Flat Roof Designs
Curved Roof
Skillion Roofs
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