FREQUENTLY ASKED QUESTIONS
1. Am I required by law to have a living roof?
If you live within the city limits of Toronto, then as of January 31, 2010, you will fall under the jurisdiction of Green Roof By-law PG25.3. However, unless you are planning to build a mansion that’s over six stories high, you will not be required by law to make your roof a living roof. Even factory buildings will only be forced to turn ten per cent of their total roof space into living roof. If your home has a floor plan of less than two thousand square metres, then greenifying your roof is completely optional. But it is most certainly advisable!
2. Aren’t living roofs a bit radical?
No, far from it. Living roofs have been built in Northern Europe for hundreds of years. The modern living roof movement began over forty years ago in Germany; today, over ten per cent of all the roofs in that country are living roofs. Living Roofs are considered to be a conventional feature in that culture; North Americans are simply arriving late in the game. If you’re interested in seeing what a real radical vision for the greening of urban areas look like, do a search for the work of Freidensreich Hundertwasser or Malcolm Wells.
3. What does a living roof consist of, exactly?
The components that are standard to all green roofs are: a waterproofing layer directly on top of the existing roof; a defensive layer to prevent the puncturing of this waterproofing layer; a drainage layer to prevent overflow in the event of a deluge; the growing medium, a layer of healthy, fertile soil, several inches thick; and the plants themselves, of course. Some roof systems also have special containers that the growing medium sits in. Although it separates the plant life into distinct containers, it enables the roof system to be built — or disassembled --with great speed.
4. How would having a living roof contribute to the environment?
Living Roofs contribute to the environment in three main ways. First of all, they increase the amount of plant life that can absorb greenhouse gases out of the atmosphere, like CO2. Secondly, they retain rainwater in their rich water, which eases the burden on municipal sewage services, preventing the contamination of our precious water supply. And thirdly, they add habitat for non-human animals that have been marginalized by industrial development almost to the point of extinction, preventing the collapse of the circle of life upon which we all depend.
5. What is a “white roof”?
A “white roof”, also commonly called a “cool roof”, is essentially a regular roof that has been plastered and painted white. Granted, there are certainly some ecological benefits to a installing a “white roof”. Light-coloured objects reflect light energy, and dark-coloured objects absorb light energy, so darker roofs are going to absorb the sun’s rays and get hotter quicker. Roofs plastered and painted in lighter colours will reflect more of those solar rays, maintaining a cooler indoor temperature and reducing your cooling bill. This is why, when you travel to the sun-soaked Mediterranean, almost all houses have white roofs.
6. Is a “green roof” better than a “white roof”?
So, which of the two systems is better? A white roof or a green roof? It is not so cut-and-dried, both of the systems have their positive qualities. But I would argue that the green roof is a more ecological roof. Sure, the white roof will reduce fossil fuel use and cooling expenses. But the green roof will reduce both your cool and heating expenses. And it will absorb CO2, and it will slow down stormwater runoff, and it will provide a habitat for wildlife. And it’s much prettier to look at! So when you take all of the positive factors into account, there’s really no contest between the two, a green roof is far more ecological.
7. What kinds of plants go on living roofs?
For all intents and purposes, there are no major differences between a living lawn and a living roof. The only caveat is that the type of plants that you use is dependent upon the amount of soil that you install, which is in itself dependent upon how much weight your roof can structurally support. And of course, these plants must be capable of surviving cold Canadian winters, just like anything that grows in your garden. That said, you can grow all kinds of edible and medicinal plants, just like you would in your back yard, as long as you have easy access to your roof. But if regular access to the roof is problematic, then you should probably stick to low-maintenance ornamental plants.
8. Do living roofs require artificial irrigation systems?
It all depends on what you’re growing up there, and what you’re going to be using the roof for. If you’ll be growing food crops or colourful ornamentals up top, then it goes without saying that they will require regular watering. But if you don’t plan on spending any leisure time up on the roof, and you won’t be able to see it from the street, then aesthetics aren’t a concern. Even if there’s a heat wave, drought-resistant plants will weather out the dry spell and bounce back when the rains eventually return.
9. What happens in the winter when the city is covered in snow?
Once again: think of your back yard, blanketed in a layer of soft snow. The green grasses have dried up and turned brittle yellow-brown. All living things with their roots in the soil have drawn themselves into the ground, much as a bear hibernates in winter. Come spring time, once the snow melts and the weather warms up, the seeds sprout again and the blades of grass poke through the earth, green and youthful. It is no different with a living roof. It won’t require replanting ever year, only a little bit of regular maintenance at the start of the season.
10. Does a living roof provide a building with any extra insulation?
Living roofs certainly do provide a measure of insulation. There is no automatically-calculated R-value or U-value for living roofs, since it is not a standardized industrial product. But there is no question that they significantly reduce the amount of heat loss during the winter months, as well as cut down on the heat gain during the summer months. And the living roofs provides not only thermal insulation but acoustic insulation; if you live in a relatively noisy neighbourhood, you will notice a reduction in decibel levels.
11. Is every building capable of supporting a living roof?
Almost every roof is capable of supporting a living roof. Installing a living roof means adding several inches of soil and a couple of layers that separate the soil from the original roof itself, and these add weight to the roof. So if the roof is poorly constructed, or if it was not engineered to withstand distributed loads, then it would be unwise to build a living roof on top of it. But in Southern Ontario, because we receive significant snowfall, our roofs are designed and built to bear the weight of several feet of snow for months at a time. So a little bit of soil isn’t going to make a big difference.
12. Can a roof with a steep pitch support a living roof?
There are several different kinds of living roof systems, and some of them are quite capable of containing the soil on a roof with a steep pitch. In fact, even if that roof exceeds 45 degrees, is more vertical than it is horizontal, as in an A-frame house, it would still be capable of supporting a living roof. In those instances, we use the same system as we would in a Living Wall. So if it can work perfectly on a straight wall at an incline of 90 degrees, then you know it’s not going to be a problem at significantly less than 90 degrees.
13. Is a living roof more likely to leak than a conventional roof?
Statistically, a living roof is no more likely to leak water into your home than a conventional roof. It is all dependent upon the quality of the work of the original roofer. True, plants will extend their root systems deep into the soil, and if proper precautions are not taken, these could puncture the roof liner, allowing water to leak through. That’s why professional living roof installers add an additional rigid layer that prevents these root systems from digging any deeper than the depth of the soil. Your living roof should last at least as long as a regular roof, and it will probably last much, much longer. And should your original roof begin to leak, we can remove the living roof layers with relative ease, and replace them after the proper repairs have been made.
14. Is a living roof more likely to catch on fire than a conventional roof?
Let’s ask this question a little differently: Is a grass lawn any likelier to catch on fire than an asphalt lot? Have you ever heard of anyone’s front yard going up in flames? Grasses on a roof are identical to grasses on a lawn, they’re just one or two stories higher off the ground. In fact, if you have a living roof and you live in Germany, you actually receive a reduction in your fire insurance premiums, not an increase! And if you still have any lingering doubts about what would happen if a living roof caught on fire, then I encourage you to view this video on YouTube.
15. Does a living roof have to take up the entire surface area of the roof?
There’s no reason why a roof would have to be exclusively used to grow plants. A solar hot water heater would make a great addition to any roof. Maybe you want to create your own electricity by installing some solar panels up there, as well. Perhaps you’d prefer to use part of the roof for a wooden deck to kick back and relax on. Or you might need a few square feet to mount an antenna or satellite dish. Any of these needs are perfectly compatible with a living roof, there’s no reason to have to choose one or the other.
16. Can I put solar panels on top of a living roof?
Sure, there’s no reason why you couldn’t put solar panels on a living roof. Solar panels are a whole other ball of wax, but in brief: you wouldn’t want to cover the entire roof with solar panels, only a small part of it, so the rest of the roof can be covered in soil. The two main reasons why you would only want a few solar panels instead of a whole roof rack full of them are that one, they are very expensive, and two, a single-family home doesn’t use enough electricity to justify the installation of so many panels. You aren’t running any heavy industrial machinery in your house, only a few appliances! So a handful of panels will suffice, leaving lots of room for a living roof.
17. Can I re-use the water that drains through the living roof?
Of course you can! This necessitates a more thorough discussion about rainwater collection. But in brief, collected rainwater can be used in a variety of ways. You can use it to water your garden. You can use it at hand-washing stations. You can use it to fill conventional toilet bowls. Just ensure that the roof drains to a food-quality rain barrel or an agricultural quality water tank, and start to save precious water. As an added bonus, you’ll be doing even more to prevent an overload of the sewage systems that pollute our fresh water lakes.
18. Does the addition of a living layer affect the lifespan of a roof?
There is debate in the industry about exactly how the installation of a living layer affects the longevity of a roof. There is consensus that it provides protection from the elements, and thus lengthens the life of its component parts. An industry organization in the United Kingdom claims that turning a regular roof into a living roof at least doubles its life. Other American organizations make even greater claims. Ultimately, if the workmanship is of professional quality, you can be sure that the living roof will last a lot longer than a “dead” roof!
19. What is a green roof on my house liable to cost me?
There are many variables that have to be factored into the equation. But to give you some general figures so that you can figure out if it’s even in the budget: a living roof is likely to run between $100 and $250 per square metre. Let’s say that the footprint of an average small building in the City of Toronto is about 35 feet by 40 feet, which would means an area of approximately 140 square metres. That would mean you are looking at an installation cost of $14,000 to $35,000. No, that’s not chump change! But it pays for itself over time. Call us with more information about your roof to receive an accurate estimation of what it would cost you.
20. Will a living roof require expensive regular maintenance?
Again, the easiest way to understand the maintenance costs for a living roof would be to think about the maintenance costs of a healthy lawn. Depending upon which varieties you choose to plant in your front yard, either they could require a great deal of attention, or else they could pretty much take care of themselves. Unless you are planning to use it as a patio, you probably don’t want to climb up on to your roof too often. So we would recommend planting the roof with hardy, drought-resistant grasses that do not require a lot of water. You certainly won’t have to pay anyone to mow your roof! Ultimately, the amount that you intervene with what’s growing up on your roof becomes an individual aesthetic choice.
For more information, check out the following Green Apple Pie articles:
To see local examples of Living Roofs, check out the following Green Apple Pie image galleries:
