Being Green – Up On the Roof

Hi Folks:

Well, The Drifters did it first…

So, I wanted to talk about roofs today, but before I get into that I wanted to start with something that at first blush doesn’t seem to have anything to do with building at all.  I think it does…

The idea for this came from a woman who was at a conference I was attending.  I don’t know her name, but whomever she is, I’d like to thank her.  I’ve used her idea several times, mostly with school groups.  Basically what I do is to gather the assembled group into a circle, produce a ball of string from my pocket, and tell everyone we’re going to recreate a simple ecosystem – say the forest or field we happen to be standing in at the time.  One person in the group takes the end of the string and s/he begins by being one element in this ecosystem.  For example, “I’m a robin.  I make my nests out of bits of twigs and leaves, I eat berries, earthworms and insects, and if I’m not careful I can be eaten by small raptors or foxes.”  While holding onto the end of the string, s/he then tosses the ball across the circle to someone else, who adds the next connection to our web. “I’m a mouse.  I live on the forest floor in my mouse house, I eat seeds and nuts and berries and sometimes small insects and things, and I can be food for snakes, foxes, coyotes, owls, and most everything bigger than me.  I make up for this by having large families.” Holding onto the string, s/he tosses the ball across the circle… and on it goes, someone being the wolf, someone being the oak tree, someone being the crow, someone being the raspberry bush, etc. until everyone is holding onto the string.  What becomes readily apparent is that we have created a simple web of life, with the string crossing and crisscrossing the circle.  Everything is connected.  This becomes more apparent when I tell everyone that I’m going to be a force that disturbs this ecosystem – could be human, could be a major storm, doesn’t matter.  I go around the circle and randomly tap people on the shoulder, and when I tap someone on the shoulder, s/he pulls on the string s/he is holding.  The important thing is that it doesn’t matter which section of the string gets pulled, the entire web moves (the fun part is rewinding the string back into a ball without tangling it).

I mention this because traditional house building isn’t often seen as integrated but as a series of unrelated systems.  There’s the plumbing, the wiring, the framing, etc.  What we’re seeing more and more with green building – LEED, Built Green, the Living Building Challenge and PassivHaus for example, is that all of these systems are and must be connected, not only within the house itself, but also between the house and its immediate environment, and even beyond that.  I mention this here because I wanted to talk about roofs, but roofs do more than simply keep out the elements.  First we have to start with the roofing materials themselves.  Probably the most common roofing choice today (for angled roofs) are asphalt shingles.  I don’t like to pick on anyone in particular, but asphalt shingles are simply a horrible idea.  They’re popular because they’re cheap and reasonably durable (avg. 12-20 years), but they’re petroleum-based, they off-gas into the atmosphere, and while it is possible to recycle them into paving material, “according to the National Association of Home Builders, in the US asphalt shingles account for an estimated 1.36 billion pounds of waste in landfills every year.“  That’s a scary number.

So, what are the alternatives?  Well, there are many.  Each has its own pros and cons.  Slate is one.  On the plus side it’s natural, reusable, and lasts just about forever – well, a century anyway.  It’s also fireproof.  On the down side, slate is heavy, expensive to install and to transport.

Metal roofs are also pretty popular.  They come in a wide variety of styles and colours, as sheets, standing seam or shingles, and in steel, aluminum or copper.  Metal roofs also have a Class A fire rating, and generally come with a 50-year warranty.  They’re more expensive to install than asphalt shingles, but they’re fully recyclable.

Cedar shingles are often considered an environmentally friendly option.  On one hand they’re light, they’re durable and long-lasting.  On the other hand, the best cedar shakes and shingles come from old growth forests.  Personally, I’d rather have the trees.

How about rubber shingles instead?  Often made directly from recyled tires, rubber shingles can offer some of the benefits of slate roofs without the weight or the cost.  Other synthetic shingles are made from recycled plastic bags, PVC pipe or other materials, heated and injected into a mold.  They usually come with a 30-50 year warranty, Class A fire resistance, and high wind resistance as well.

One attribute all of these options share in comparison with asphalt shingles is a higher up-front cost.  Some of them can be four to five times as much as an asphalt shingle roof, but one must weigh those costs out over the long term (if you have to replace your shingle roof three times over the lifespan of a metal roof, is it cheaper?) as well as the environmental costs.

Another factor to consider for roofing, whether residential or industrial, flat or angled, is colour.  Black roofs absorb a lot of heat, and in the summer that will add considerably to the load of the building’s cooling systems.  Not only that, but in urban environments the collection of extra heat from all of the buildings can create what’s known as a ‘heat island’ effect. There are many options today for white roofs for commercial buildings, and while the average homeowner will likely shy away from having a white roof on their house, a lighter colour, no matter the material, will be of benefit.  Something to consider.

Speaking of colour, I wanted to mention two specific ‘colours’ – green roofs and blue roofs.

Green roofs are sometimes called ‘living roofs’.  Most common on flat roof surfaces, green roofs incorporate living plants on the roof itself.  It is possible to put a green roof on an angled roof (depending on how steep the pitch), and there are even ‘living walls’.  One example of this is a building recently completed in Sao Paulo, Brazil by Triptyque Architecture.

In 2001 Mayor Richard Daley of Chicago began a project to create green roofs in the city by building one on top of the Chicago City Hall.  Upon completion it was discovered that the green roof was up to 78 deg F cooler than the black roof on the Cook County building and the new roof contributed to lowering the cost of cooling the city hall building by $5000/year.  There are currently over 400 green roof projects in Chicago.  Toronto‘s green roof legislation came into effect this year. “The regulations will require green roofs on new residential buildings in the city starting January 31st 2010 that are more then 2,000 square meters and 20 meters or higher. Industrial construction will have an extra 12 months to prepare for the requirements. For industrial buildings they will have to reserve either 10% of the roof area or 2,000 square meters, and have the option to choose the lesser amount for sod and other greenery.”

Green roofs begin by adding a waterproof membrane, over which a depth of soil or growing medium is added.  There are two general classifications of green roofs – extensive and intensive.  An extensive green roof has a thin layer of growing medium and is designed to be low maintenance.  In contrast, an intensive green roof has a much greater depth of growing medium and can support many types of plants, including trees.  Intensive green roofs are often called rooftop gardens, and can be used to grow ornamental or food plants.  At Changi General Hospital in Singapore, organic vegetables are grown hydroponically on the roof and the harvest is used to feed the hospital’s patients.  Similar ideas are ‘taking root’ throughout the world.  The home of the American Psychological Association in Washington, DC has a green roof that also incorporates a meditative labyrinth.

The benefits of a green roof are many.  Biophilia may be the biggest one, but there are both financial and environmental benefits to green roofs.  On the environmental side, green roofs can reduce the ‘heat island’ effect, filter and remove toxins from the air and rainwater, reduce rainwater runoff/ provide stormwater management, and create micro-habitats for wildlife.  On the financial side, green roofs increase a building’s value, protect the roof from environmental damage and lower heating and cooling costs.  Green roofs certainly aren’t ‘new’, they’ve been in use for thousands of years, but they remain an excellent idea and one who’s time has certainly come.

So, you’re thinking to yourself, that sounds great, but what about irrigation?  Isn’t there already a shortage of potable water in many municipalities?  What about desert regions?  Valid points, but there are a couple of options.  One is graywater recycling.  The water that goes down the toilet is considered ‘blackwater’; the water that goes down the sink, shower drain, from a washing machine, etc. is considered ‘graywater’.  Much of this graywater can be filtered and reused for irrigation.  In fact, a building built to the Living Building Challenge standard insists on it.

Another consideration is what’s known as a ‘blue roof‘.  A blue roof isn’t dictated so much by its surface material or structure as to its relationship with stormwater.  See the ‘everything is connected’ paragraph at the top of this post. From Wikipedia: “A blue roof is a roof design that is explicitly intended to store water, typically rainfall. Blue roofs can provide a number of benefits depending on design. These benefits include temporary storage of rainfall to mitigate runoff impacts, storage for reuse such as irrigation or cooling water makeup, or recreational opportunities. Blue roofs can include open water surfaces, storage within or beneath a porous media or modular surface, or below a raised decking surface or cover. Blue roofs that are used for temporary rooftop storage can be classified as “active” or “passive” depending on the types of control devices used to regulate drainage of water from the roof.”

So, let’s build a garden together and then we’ll visit for a while, ‘up on the roof’.

(my Being Green Squidoo page)


The links for this week are:

“It is not impossible to integrate sustainability into early stages of design. Cradle-to-grave environmental impact analysis methods are rarely used as a metric during product development. In early stages of a project, companies measure feasibility according to money, performance and time metrics. Sustainability is commonly measured at a design cycle’s end on finished products when design features cannot be easily modified for sustainability measures. It is ineffective to apply new design metrics to finished products. Evaluating the ‘greenness’ of products is typically done to market the ‘greenest’ product in a line. This does not address the need to create sustainable products at project onset; thus, products remain ‘un-green’ and unsustainable.

It is time for new feasibility metric — Green Design with Life Cycle in Mind. Green design thinking must be accessible and applicable to product development through a set of tools designed for early stages of product development.” ~ Kimi Ceridon

6 Replies to “Being Green – Up On the Roof”

    1. tomarciamae

      Hello Garden Beet!

      You asked the question: blue roofs — are there many built examples?

      Sorry the 'blue roof' link in our post didn't come through – we've since fixed it. Here's that article – with info on existing application of blue roof technology – Reply

  • growth hormone

    Great information… thanks for your review and tutorial about how to comment. I think if we walk to other blog we must comment to give appreciate for owner..

  • Anonymous

    Just checking out your article on my new Garmin Phone , and I wanted to check if it would allow me comment or if it made me go to a pc to do that. Ill check back later to see if it worked.

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