As some of you know, greenroof design is nothing new. When Cortez marched into Mexico City, he and his soldiers were amazed at the beauty and food-growing capacity of the rooftop gardens they found. In Scandinavia grass-covered, super-thick sod rooftops have been around as long as the ancient sagas. But somehow, we've lost most of that and, as with so many things, now we're starting over. And while from an energy-savings standpoint alone, vegetated structures should be a home run, getting used routinely on buildings from average private homes on up, instead, greenroof is still seen as a boutique sort of thing. A luxury reserved for special case use by large institutions, the wealthy, and corporations anxious to buy some good press.
Almost all of our modern "experts" in this field start by assuming that maximum possible rewards are quite small, so they start by assuming a total budget that must be even smaller. Since they are assuming a very small budget per square foot, anything that would take "real money" is, right off the bat, declared "impossible."
They don't consider significantly strengthening the rooftop. Or having a few deep wells of soil bridged with a shallower bed of growing medium. Or trellises as part of that rooftop setup. Or sacrificing any space inside the building to gain room for either better roof access or for area for those possible structural reinforcements. Nor do they consider vegetating approaches limited to areas near existing load-bearing members. Or relocating any building tenants, either permanently or just while construction is under way.
So they then pre-emptively dismiss most buildings as "unsuitable" without ever having even considered most of the possible options. They are mixing up their prejudged idea of reasonable with the vastly larger range of what is possible. And then telling others that greenroof is "impossible" for most buildings.
At Portland's recent ecoroof show I think I was finally able to put a last few crucial pieces into place in my understanding of why.
When I first starting looking into greenroofs and doing my first small experiments, long about 1991, the people I talked to about it, most notably Paul and the other folks at the Gaia Institute, justified it first and foremost as a means of superinsulating the roof. Once one of these puppies goes in the top floor tenant's in the cool shade forever. And finds it much easier to keep warm when the outside gets cold. It was also something thought of as being done on older buildings such as five to seven story rowhouses in poor neighborhoods. Some of them about a hundred years old. And it was being done largely with variations on the mix the Gaia Institute was then pioneering, made almost entirely of post-consumer materials like styrofoam and food waste.
Let's go over that again. How things were then:
- Biggest known advantage: massive reduction of energy consumption.
- Typical project: old building rehabbed on a small budget by a small team.
- Typical composition: heavy membrane covered with a growing medium made mostly of processed "waste".
Those of you who knew me in the early nineties were subjected to my endless lectures on this, as well as "guided tours" of whatever my latest planter design was turning into or whatever plants had just done whatever unexpected thing. I know that a few of you also saw the displays that the Gaia Institute had up in the Cathedral of St. John or the projects visible on nearby rooftops.
And I can tell you that in the years after that I saw greenroof stay marginal and continue to be unknown to most builders I discussed it with. Or, at best, perceived as impractical or simply impossible for their sites. Part of the reason that I spent the years that I did with This Old House Magazine, Architectural Record, Engineering New-Record, and others in the "shelter" world was to keep track of this field and get access to their experts and libraries. And I found there and elsewhere that marginal position was pretty constant, in terms of projects planned, funded, and completed, as well as in perception among engineers, architects, and even landscape designers. Even among squatters, who were sometimes more than willing to build photovoltaic systems and other ambitious "green" projects, it just wasn't taken seriously.
But as time passed I noticed a trend. The publicly cited "experts" shifted from being builders and experimenters with dirt on their hands at small, out-in-the-field, practical firms to being paper-pushers and desk jockeys at massive, glossy firms like SOM who had been designated the in-house suit for coordinating elegant, high-budget implementations on purpose-built small segments of hundred million dollar corporate complexes. Greenroof became a way that wealthy firms provided a last, small touch of class to a large, institutional project. A rooftop courtyard garden for a very rich hospital. Vegetated swaths on the one rooftop of a corporate campus most visible from other campus rooftops. I started to see a lot more CAD flythroughs and considerably fewer self-managed projects.
But I also found a non-obvious limiting factor. One trend in that period had annoyed the bejabbers out of me. With all that nineties enthusiasm for breaking free of the anonymous glass box, they started building all these things with setbacks that just begged to be done as greenroof. In fact, some of them explicitly referenced Edwardian and Deco architecture such as Rockefeller Center, that had originally been designed to be overflowing with living things. So with their wealthy corporate clients and all their desire for high valuations, why the frack weren't these "New Traditionalists" planting all these rooftop courtyards and balconies, etc.?
It wasn't until I was at a presentation by some of the senior team members of New York City's Worldwide Plaza that I got an answer. At the reception afterwards I was blunt in my enthusiasm and my frustration and was all ready to go into evangelist mode. And they cut me off and started going into rich detail about how the original plans had included intentions to vegetate every last horizontal surface larger than a stick of gum. Oh, they were quite eloquent and very well-informed. So what had stopped them?
Insurance, they said. No insurance company would provide a policy for those surfaces. How did they know tenants wouldn't go out on them and fall off the building or even just snap an ankle or drop a glass off the side? How did they know the membrane wouldn't tear and pour water and soil on the tenants below? And so on. No data, no actuarial tables. No actuarial tables, no precise, controllable calculations for risk. No risk tables, no policy.
And while in the decade and half since some data has been put together and that issue has faded, at the time it, as far as I can tell, considerably dimmed the flame and discouraged another generation of designers from building vegetated structures.
And then it all changed.
Several factors were all creeping up on us. Municipal budgets were getting stripped. City populations were growing without proportional additions to infrastructure. And laws about public exposure to toxicity were being passed and/or stiffened, sometimes with real enforcement powers. Add all of this up with global climate change and a few other factors and cities began to be in a crisis about managing stormwater peak loads.
For those of you not familiar with this issue, there are a few parts. First of all, many cities were built so that when the drains off city streets and from downspouts and so on that were meant to handle runoff during storms reached capacity, they overflowed into the sewage system. Which then sometimes itself overflowed. With a mix of stormwater and sewage. Into rivers, parks, estuaries, and so on.
And the most commonly accepted "solution" to this was building treatment plants where that stormwater could now be routed, pretreated, tested, and released "in a controlled fashion" to some adjacent waterway.
Well, let me tell you, from a typical city hall perspective, this sucks ass. Now you need to go hundreds of millions of dollars into debt, force some neighborhood to let you build this huge muckin' grey, ugly, government facility next to them, and, now that your citizens think of it as toxic waste, they're going to fight you tooth and nail about the smell (even if you prove that there is none), how you store and ship away the resulting "collected matter", and where you release the resulting cleaner (ish) water. That they won't really believe is clean. You're looking at possibly fifteen years of expensive, unpopular and required activity and the citizens will, no matter what, blame you. After all, they were doing well enough *before* you got there, right? And why can't you just put it all somewhere else?
Other than the excuse to eventually maybe grant government consulting and construction contracts to some of your favorite campaign supporters, this is pretty much one enormous barrel of aw, sh*t. And one that, unless you find a route-around, you can expect to be drinking out of for the rest of your time in office.
Now the biggest factor in increased loads was runoff per square block. Not total city size but population density. And what increased that runoff was replacing "soft" and therefore permeable surfaces (lawns, fields, street tree planters, etc.) with "hard" and therefore impermeable surfaces (asphalt, concrete, and so forth). Even if a "soft" surface was thin, it still reduced runoff somewhat and, usually good enough, what runoff did come anyway trickled through it to drain off over the course of hours or even days, instead of what happens on a surface like an asphalt-surfaced rooftop which starts adding load to the stormwater system in as little as a minute.
Because, you see, it's all about minimizing those peak loads.
So this all changed when the city of Toronto was found to be required by law to build a stormwater treatment plant.
Well, like all cities, partially they just contested the findings. And did all the usual stuff of preparing to review plant design bids and so on. But they also did something new. Some folks up there did a very smart analysis. They said, "wait a minute, each square meter of greenroof reduces peak runoff by X and costs Y to build and operate. While a plant to treat X amount of runoff costs (greater than Y) to build and operate. So instead of building this great muckin' water treatment plant, we could save money by instead subsidizing greenroof."
So governments started, one by one, encouraging greenroof. Mostly with tax write-offs and incentives that were structured in ways that appealed most to large organizations. Places where their stormwater tax bill added up to serious money. Places of the sort where adding a few dozen more pages of forms and documentation to their yearly tax filings was no big deal.
So, at long last, that become the way that greenroof starting getting more penetration. And it meant that the people inside the client's companies who were put in charge were people from the departments seeking to cut their annual taxes, from the departments seeking to avoid fines for violating environmental regulations.
In other words, the projects were being run and judged on efficacy by people like compliance officers, who saw this as just one new tool to keep government problems minimized. The cognitive framework wasn't first and foremost about positives pursued because it (greenroof) inherently appealed to them but rather about compliance with regulations and minimizing of risk. "How little expense will make them go away?" not "how much of this desirable thing can we afford?"
And the people in government in charge of encouraging this were (and are still) judged by the same kind of standard. Not "is our city now a healthier/more fuel efficient/biodiverse/whatever place?" but "how much closer have you taken us to not needing to build a goddamn hundred million dollar water treatment center?
And, as with so many other things, the relevant municipal official were given very little money or new staff to accomplish this with. Even in cities like Chicago and Toronto and Portland, those being put forward as the trailblazers, in reality funding support was really a sad few civil servants with maybe a few graduate students from a local architecture school and some projects being built as part of some new government-funded facility.
So just about every project involves six rounds of proposals. And maybe a few of bids. And a lot of the time the funding falls through. Or the project is refocused. So a new committee is formed and it all starts over again. And every time the whole shebang needs to be rejustified. Largely to people who don't see the point, are short on funds and time, and are asking (reasonably enough) for good, hard numbers on why this is even being considered.
And I can tell you that most of the time the numbers of those justifications are described the same ways over and over and over. "Our stormwater tax is X2. The Incentive funding available is Z. The cost to build is Y2."
And I'll bet that by now most of you reading this have forgotten the biggest reason that greenroof had been getting pushed in the first place.
Remember what I said in the very beginning?
Heat. A properly built greenroof cuts your heat loss to pretty much zip. And in our new world of triple-glazed windows and air walls and so on, especially for a new-ish large building, the losses from the sides of a building that takes up half a city block and is twenty feet tall just aren't that big a percentage.
So, I ask you, how big is your water bill? How big is your heating and air conditioning bill?
If shrinking your water bill is your total justification, how big a budget makes sense?
If NOT HAVING a heating or cooling bill is a possible justification, how big a budget makes sense?
But somehow, as I walked the (pretty much empty) aisles of the Ecoroof show (I would guess that there were about sixty tables and fewer than three hundred attendees) I always asked for the selling points of every (growing medium/contractor's work/tray system/etc.) and nobody even mentioned comparative insulating value. Or mentioned it as a reason to build a greenroof.
The range of reasons they *did* give has broadened and improved, partially because the greenroof work now being done has also improved. In addition to stormwater, people mentioned heat island effect. They mentioned species diversity. They mentioned improving real estate values. But nobody said any variation on "this will reduce your heating and cooling bill." They had charts and graphs with information on water held per square foot, cost per area installed, cost of maintainance, species range, animals found nesting on similar systems, and so on. But on insulating value? Nothin' and nothin'.
And after a while I started asking everybody the same question. "Have you or anybody ever collected temperature performance data on installed greenroofs?"
You know. Put one sensor each above and below a bare section. Another matching pair above and below a vegetated section. Hook them up to a computer. Log the data. Do this on a few dozen buildings. Publish the results.
I talked with everybody I could reach, including the relevant Portland city officials and several of the other speakers, considered world-class experts, including quite some time talking with the Director of the International Green Roof Association, Wolfgang Ansel, who flew in from Germany for the event.
And as far as any of them knew, nobody has ever done this simple thing. There is no real statistically usable, controlled, significant scale data of the sort that would make it possible for greenroof to get remembered to be in addition to the things it's thought of as now, a vastly more capable potential cost-reducer and resource-saver.
For the lack of what most of them readily agreed was about a $10,000 study, we are ignoring one of the fastest, cheapest ways we have to massively cut world energy consumption.
Because most of the relevant people have forgotten to even think about it and those who haven't have all decided that this job is simply somebody else's problem.
And because this factor is usually thought of as an undocumented "oh, by the way" HVAC operational cost reductions don't get included when people calculate when greenroof is appropriate. Which leads to that crippling fallacy. As I wrote at the very beginning of this essay, most of our "experts" (Paul Kephart being one glorious exception) start with the presumption that a greenroof project is being done as a bit of a cost game by a grudging organization whose total maximum return on investment will be quite small. So they START by throwing away consideration of every option that would cost "real money".
No serious bracing of the roof. Certainly no bracing that would reduce in any way the amount of space available inside the building.
No large, enjoyable staircases or new elevators up to this wonderful beautiful place.
No incorporation of new ductways or service shafts, let alone an internal "dumbwaiter" to move all that heavy water and plants and so on up and down. So the builder/contractor will be, in effect running a huge landscaping job with nothing but cranes and equipment that they will have to bring with them every time they have work to do.
No consideration of the viability of getting the building repermitted to allow residences or a restaurant or some other installation that would further turn that newly green surface into a revenue generator.
And on and on and on.
By starting with ignoring the relevance of some of the biggest relevant cost justifications, our engineers/architects/project managers are throwing away any willingness to consider most of the means they have available to make greenroofs work.
Having then started by reducing their options to almost nothing, they they sit on their high perches and dismiss most projects as "impossible". And keep in mind that I still haven't even mentioned some other key factors. For example, facilities managers all over the world are finding themselves these days needing to provide new seismic retrofits. And yet none of the contractors I spoke to mentioned those considerable projects to add beams and brace walls and otherwise do comprehensive structural revamps as chances to make a building better suited to deep bed greenroof or even for greenroof at all.
Nor have we gone into how many commercial districts are converting to mixed use, complete with children and schools and, rather frequently, in areas where all the land is already long since spoken for, new pressure to create more park space. This is frequently now addressed by spending millions of dollars and going through a vast, many year circus of public hearings and funding rounds premised on buying existing buildings, forcing out the tenants, demolishing everything, and creating parks where those buildings once stood. Mightn't it make more sense to instead build greenspace right on top of the one of the shorter buildings that are there right now? Perhaps with a nice twenty foot wide ramp up to the new public space from street level?
But that's now what we do. Instead, we have a paltry few hundred buildings in even the best cities, usually partly covered with thin, near-monoculture beds of very short plants, all installed at massive cost per square foot by people who tell us that this is the only option we've got.
Does this seem like the right approach to you?