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Archive for January 2018

Berlin’s Potsdamer Platz, an amazing urban runoff control system

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The development from the air, showing some of the green roofs

When I was in Germany I went to Berlin, a few times.  That included going to Potsdamer Platz, more than once, sitting under the dome of the futuristic Sony centre, meeting friends for coffee.

All the while having no idea that I was right in the heart of one of the most advanced urban runoff management projects in the world.  Completely missed it.

I suppose it’s no surprise; much of it is below ground, and much of it is on the roofs.  Still, it bugs me.  Here’s what I found out about it – after the fact.

First, some background: this is a large site smack in the centre of Berlin.  if you look on Google Maps, it’s bordered by the Landwehr canal in the south, Linkstrasse to the left, and the curve of Potsdamer Strasse to the west and north, and Marlene Dietrich Platz is right in the middle; despite the name, the historic Potsdamer Platz is just the north-east corner.  The firm Dreisetl oversaw the development project.

This is an area that was bisected by the Berlin wall, with a large no-man’s-land on either side.  It’s in the resulting wasteland that most urban renewal projects were constructed in Berlin after 1989, and the whole complex of Potsdamer Platz itself, including the area around Marlene Dietrich Platz, is just one instance.

So here’s what I walked over and didn’t even see.  The development captures rainwater from the roof of its nineteen buildings, thanks to 32,000 square meters of green roofs.  Not all the surfaces are green roofs (the extensive type, with allium and sedum), but the amount is sufficient to intercept 61% of all rainfall.  Much of what is captured evaporates away (31%); the rest eventually runs off to the five large cisterns underground.

What this means is that the system can hold a ten-year storm, the kind that could otherwise result in local flooding.  Instead, the rain water is captured; about 60% of the amount in the cisterns will be used for irrigation, while 40% is used (after cleaning) to flush toilets – and create a reserve of fire suppression water if needed.

This is quite significant; the green roof water is used whenever available, saving municipal drinking water; about 20,000 cubic meters of good drinking water are saved every year (that’s enough water to fill 250 bathtubs, every day, for a year).

And whether the water is reused for flushing or for irrigation, it is cleaned up along the way.  It is stored in a pond called a “cleansing biotope”.  There the water is filtered through a porous media that is mostly sand, but also includes 5% of lava rock, which chemically binds down and remove phosphorus.  The biotope, open to the air, is a design such that water has a retention time less than three days, which is too short for microscopic algae to establish themselves.  Much of this information, and more, can be found here, here, and here; the video below also gives an excellent idea.

What the public sees – and what I walked by without noticing – is just a nice water feature to the side of the buildings.

I also missed – but the public cannot visit – the green roof of the Canadian Embassy on nearby Leipziger Platz, one designed by landscape architect extraordinaire Cornelia Oberlander, a design said to be a scale model of the Mackenzie River Delta.

And Canada House, as our embassy is called, is not even part of this development.  But this shows how common are green roofs in the city; even if climate change causes worse storms over Berlin, or extra long droughts, the city’s initiatives mean that it is in great shape to absorb it all without flooding, or – at least in Potsdamer Platz – to keep flushing without running out of water.  There is something to be said for being proactive.


Written by enviropaul

January 25, 2018 at 8:10 pm

The most environmentally-friendly office building in Berlin

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The ministry of the environment building in Berlin

In my last post I wrote about how in Germany the various Environmental government branches put their money where their mouths are, producing remarkable buildings with low footprint such as the BSU in Hamburg or the UBA in Dessau.  I also mentioned how its engineers and architects are not afraid of trying something new and learn from what doesn’t work.

Given that context, then, imagine being tasked with the remodeling of an old historical building in the centre of Berlin into a showcase of energy efficiency.  The client wants the design to use and respect the architecture of the old building, a former pre-war Ministry of Agriculture facility.  Also, the architect must acknowledge, in the design, that the building was part of the wall (its western half was boarded up) and that heritage must be manifest.  Building materials must be non-toxic, with a low environmental footprint.  The building is to be high-security, but accessible by the public during special functions.  And the building’s energy use must use the PassivHaus standard (that is, 15 kWh/m2; this is the equivalent of using an ordinary hair dryer to heat an entire house).  Final detail: this is the building where the client, the minister herself, Dr. Barbara Hendricks, is to have her office, so it better be comfortable, practical, as well as an attractive showcase for visitors.

The original building in the 1920’s

Phew.  If the project had been offered to me, I would have said “pass”.  Who needs the headache?  But apparently, some architects salivate at this kind of challenge.  Berlin architects Pleuser, Maass & Geier won the contract.  The building on the half-hectare site, 128 Stresemann street, with over 16,000 m2 of floor area, was completed in 2011 at a cost of 67 million euros.

Dinah and I visited the building, called BMUB.  I had no idea it was high security; past the little lobby is a heavy door opened with a security code.  Ah well, at least there is a rack with some brochures.  I was about to turn back (I give up easy) when two women appeared on their way out. Dinah spoke to them; it turns out that, yes, they were from the Ministry, in the equivalent of Outreach and Education branch.  And yes, they’d be happy to show us the building.  (Yeah Dinah!)

The historic courtyard, now glazed over

It was cool to see the historical inner courtyard, which is open to the public at times for concerts or exhibits; it is now enclosed with a transparent ceiling.  It was also very nice to see a remnant of the wall, incorporated, museum-like, into the new wing of the building.  But otherwise, it’s just a big office building, nothing spectacular.  As always in energy efficient buildings, the air feels fresh and crisp, thanks to the heat-exchange ventilation.  But maybe a bit too crisp; I learned from our guides that the air was much too dry at first.  This may be because some of the inner walls are made of ordinary clay; maybe it took a while for the clay to reach the right moisture content.  Whether or not that was the cause, the staff adjusted by hanging wetted drapes here and there in strategic spots.  We were told that this is no longer an issue.

I could picture some engineer getting a dressing down from the minister.  In fact, there were all sorts of surprises associated with the project.  Unbeknownst to the designers, there was a bomb shelter in the basement, which took a long time to remove since using explosives would have threatened the existing structure.  There was an unidentified black adhesive covering the basement floor, which had to be stripped carefully and disposed of as a hazardous waste.  When digging for the new wing, it became clear that it had been contaminated by oil; the designers adjusted by digging further, removing the contaminant, and creating a second basement floor.  One can just imagine the expletives.  And the designers of the solar panels realized, half way through, that a new building going up in an adjacent lot was going to create shade, forcing a redesign.

You have to admire the perseverance of the team; others would have compromised.  But as Uwe Rӧmmling, the ministry’s Energy Officer, said:

You need a firm commitment on the part of the owner.  There must be no capitulation if costs increase or deadlines cannot be met.  In this case, the owners remained firm.  The target was clear from the start and very ambitious.  The owners not only stated the energy levels they wanted to achieve, but also specified verification methods…Of course, with such a showcase building, we have to show the Federal Court of Audit and the Federal Ministry of Finance that our solutions are cost effective.  The problem here is that many of the positive effects of the building are difficult to express in euros and cents.  Climate, health and safety, resource conservation, pollution reduction – we have done good things in all these fields.

The building, unprepossessing as it may look from the outside, has since won several design awards, including the European Architecture Prize 2012.  And so it should: it is the federal government building with the highest energy performance, while incorporating and restoring historical elements.

A part of the wall on display in the new wing

There are many more details that are available in the booklet I picked up there, Constructing sustainability.  Unfortunately it is no longer available on the ministry’s website, but it can be downloaded from here.  For anyone who wants details about the green roof (sedum), or the geothermal system (sewer heat), it’s all there.  Along with this little quote, a very typical German one, about opening windows: “employees are called upon to show environmentally aware behaviour.”  Jawohl!

UBA in Dessau (another great environmental building)

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The UBA building in Dessau

In my previous post I described the BSU building, home of the Ministry of the Environment of Hamburg.  It is a high efficiency building that shows that the Ministry is putting its money where its mouth is: as it is dishing out incentives for energy conservation (and regulations against wastefulness), it spent money on energy efficiency for itself.  That means that it can point out to a successful example as well as try out innovations.

An overhead view of the site

This is matched by initiatives from its federal counterpart; we had a chance to visit the Federal Environment Agency building in Dessau (the UBA building).  Designed by the same architect (Sauerbruch Hutton), it’s a twin to the Hamburg building: a long-slung, snaky building designed to maximize natural light.  As in Hamburg, it has a large atrium open to the public, but this one is glass covered. The four-story building has 18,700 m2 of floor space, and parking space for twice as many bicycles as cars.

We visited on a sunny Saturday morning in July.  The big atrium was bright, the air was fresh (there are trees growing indoor), the place felt remarkably inviting.  And it’s particularly remarkable for Dessau; the sleepy Saxon town may be famous for being home to the Bauhaus movement, but most of the architecture around are pretty bland, Soviet inspired flats.  The historic downtown, what’s left of it, is a bit meh (and a meal of rotkohl overpowered by cloves didn’t help first impressions).  But visiting the UBA building before we left (we only had one overnight there) made up for it.  The building was an initiative of the federal government to bring back jobs and a bit of sunshine to a town whose economy was wrenched by the fall of the wall in 89.

The UBA building had a few design challenges placed on it: it is built on what was a contaminated brown site (an old gas plant), and the building had to integrate the historic train station.  And if the BSU building in Hamburg had to be energy efficient (at 70 kWh/m2), the Dessau building had to be under 62 kWh/m2 total; that is, for heating, cooling, and electricity combined.  Quite a tall order.

The building uses 655 m2 of photovoltaic panels for the bulk of its electricity.  It uses natural ventilation when outside temperatures are between 15 and 23 C; when the air is outside those limits, it uses forced air ventilation with a heat-exchanger.  Sure enough, when you walk inside the building, the air feels fresh and the building quite comfortable.

Inside the spacious atrium

The building also uses an absorption cooler for air conditioning (a big energy demand in any large building), and the source of heat for the cooler is a series of thermal solar panels (I know – heat for the cooler?  Huh?  But that’s how it works, take my word, or look it up if you’re a geek).

But the really innovative part of the design is the geothermal heat-exchanger – or maybe a better name for it is geothermal heat storage.  In front of the building, buried 2 to 4 meters below ground, run over 5 kilometers worth of tubes.  Outside air is pumped through these tubes; at that depth, the ground remains at a pretty constant temperature, so the air is cooled in summer and warmed in winter.  The pipes were laid with a small slope (2%) so that any condensation water can run down and be collected.  This was indeed one of the worries about the design: stagnant water in ventilation systems is what led to Legionnaire’s disease.  Further, as radon gas naturally seeps from the ground, complete sealing of the pipes was required.  Routine tests (radon, microbial pathogens, etc) show that the air piped into the building has a better quality than outside.

The ground-based heat-exchanger works beautifully, even if it isn’t as efficient as originally designed.  I know this because the literature on it, destined for the general public, is upfront about it.  I love the transparency, and I also love the fact that German engineers are allowed mistakes on innovative systems.  When you design something, you may play it safe – and learn nothing.  Or be daring, and learn from mistakes.  This has been the German approach, and it paid off in spades; no wonder the country is a leader in innovation.

The landscaping of the site is pretty impressive, too.  The 2.7 ha site was a highly polluted, dead zone.  Thanks to decontamination and extensive soil removal (which led to the decision to use a ground-based heat exchanger), the site now has over 11,000 trees, hedge shrubs, ground-cover or aquatic plants, as well as nesting boxes and insect hotels.  German designers are nothing if not thorough.  Fifteen years after completion (this was a side project of Expo2000 in Hannover), the building still feels new but the site has this lush, well established verdant look, and the trees inside the building are radiant and healthy.

Maybe Dinah and I lingered a bit too long; Dessau was a stop on our seven-day bike trip, and the next leg to Torgau was our longest one.  But it was a gorgeous (if windy) day, we cycled along the Elbe on dedicated bike paths rolling through a forest and over a bike/pedestrian only bridge across the Mulde.  Pretty nice for what once was depressed, grey East Germany.

Written by enviropaul

January 18, 2018 at 10:49 am

The BSU building in Wilhelmsburg

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One of the buildings I wanted to visit soon after Dinah and I had settled in Hamburg was the new BSU (Ministry of the Environment) building in Wilhelmsburg.  It’s the highest building in the neighbourhood.  Dinah came along, though she had her doubts: how interesting could a government building possibly be?

I didn’t need to worry.  The big and colourful building has a large open foyer that held a huge scale model of the whole city.  We had fun locating the large courtyard of Stephan and Anya’s apartment in the Ottensen neighbourhood.  And weren’t alone; there was a small crowd going about, gawking at the model, like us.

The fact that there were so many people is one aspect of a new policy of openness.  The main foyer, the library, even the employee cafeteria, are all open to the public.

There were also many brochures and booklets about environmental initiatives, another expression of outreach.  But it was the building itself that interested me.

It’s a long, snaky, colourful building designed by Sauerbruch Hutton from Berlin.  It was built as part of the Hamburg 2013 IBA (the international building show, where various architects compete to produce original buildings). The main part of the building is five-story tall, with one thirteen floor tower.  The building allows for natural ventilation, and is designed to maximize natural light.  But it’s also energy efficient; thanks to excellent insulation and triple-glazed windows, its annual consumption is only 70 kWh/m2, or about four times less than the usual amount.  And sure enough, despite the crowds, the air had this fresh feel that I have come to recognize in energy-efficient, well ventilated buildings.

Kristian, the PhD student who guided us through the building

I was wondering how could I find more information about the building when Dinah came back with a security guard who said that there is a student working in the building who could give us a tour.  Wow.

We were introduced to Kristian, a PhD student tasked with monitoring the energetic performance of the building.  He took first to the roof of the tower.

What a view!  We could take in all of the IBA site around the building.  It seemed every IBA building had solar collectors, or a green roof, or both.  The BSU building itself has a green roof, with an interesting mix of species; this includes flowering plants, as there is a plan to bring hives.  Beyond the IBA, we could take in a complete panorama: the old apartments of the residential area of Wilhelmsburg (with the unique Energiebunker among them), the harbour, the copper mill, the Moorburg coal plant, and the sea of white tents of the refugee camp (long since gone to better digs).

The view from the BSU roof, with IBA buildings below

We were then taken to the bowels of the building, where Kristian shares his office with another student, Peter.  There, in the labyrinth of pipes, tanks and cables, is the reason for the energy efficiency of the building: a vast geothermal network.  Over a thousand wells have been dug below the building down to about 18 metres.  One of the unique features of the system is that these wells serve both as a geothermal energy system and a structural support system: each well receives a rim of rebars and a twin, U-shaped set of ascending and descending 3 cm diameter pipes.  Once that has been pushed down to the appropriate depth, the well is filled with structural concrete.  Through the pipes circulates a heat exchange fluid that either stores or extracts heat from the ground, connected to heat pumps, for both heating and cooling needs.

This is a very large system, even if the building itself is big; that’s because it is coupled with the new district heating system.  Aside from the heat pumps, the basement holds a cogen power plant fed by biogas from the city’s wastewater treatment plant, capable of producing 500 kW of electricity, along with 700 kW of heat, a 20 cubic meter tank for buffer storage hot water, and two 1.5MW gas boilers for peak heat demand.

Peter, Kristian’s colleague, at his desk, monitoring the building’s performance.

This is part of the so-called “integrated energy system”; it is only one of several buildings that can also produce heat and/or electricity.  Demand and production varies between the different building, making energy savings possible by optimising production between buildings.  For instance, if a partner generator is producing a large amount of solar heat, more than it itself needs at the moment, the excess heat can be piped into the network, and the cogen plant reduces its output.  The other generators integrated into the network are the BIQ house (otherwise known as the algae house, it is the only building in the world with a bioreactor façade), the Smart-is-Green building (which uses a phase change material to store energy from its large solar thermal array), and the Water Houses (with another large solar thermal array).  Beyond this, but not part of the integrated control system, are the windmills of the Energieberg, and the large generating capacity of the Energiebunker, all developed as part of the IBA.

Part of the Water House with BSU in the background

Part of what makes this integration possible is a high degree of instrumentation.  Embedded in several of the pipes are fiber-optic real-time temperature sensors that constantly monitor the performance of the underground system.  Kristian and Peter explained their research: they analyze all the data from the system to see whether it is indeed as efficient as the designers aimed for, whether there are trends that show that the performance may be diminishing with age (they plan to keep at it for another two years), and whether there are more energy gains that could be realized.

Flowers on the BSU green roof

This research is maybe what impressed me the most about the whole building.  It’s one thing to have fancy designs that result in fancy buildings.  That, we do a lot.  But it’s another level altogether to constantly monitor and check whether the system is actually working like it is meant to.  And it’s yet another thing to have a policy of openness and transparency.  I hope this gets copied widely.

We thanked Kristian and Peter, and went on to find some German pastries.  That’s my kind of tourism.

Written by enviropaul

January 15, 2018 at 11:15 am

Kronsberg – a model neighborhood in Germany

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Kronsberg from the air: it’s the rectangle in the centre, right of the tram tracks

Hannover, the old centre

When Dinah and I were in Germany for a few months, one of the first places we stopped at was Hanover.  The capital of the state of Lower Saxony, it’s the ancestral home of the British royals, and of such notables as Gottfried Wilhelm Leibniz, inventor of the calculus.  It’s a smallish city of half a million, with a pretty historic centre.  But history wasn’t the main attraction for me; I wanted to visit a neighborhood called Kronsberg.

Kronsberg was developed along sustainable principles for EXPO2000, hosted in Hanover.  I was curious to see what it looked like, and whether, fifteen years later, it had lived up to its lofty environmental and social goals – including affordable, energy efficient housing.

Kronsberg may be a bit unusual in being located on the very edge of the city, nine kilometers from the centre.  Usually, such planned developments are on old industrial sites such as HafenCity in Hamburg.  Dinah and I took the tramway from downtown got off at the very last station (you could see farm land at a distance).

On the tram

I love tramways – such a relaxing way to travel and see a city.  In Germany, dogs are allowed on tramways (great for people who want to take their dogs for long walks on the outskirts without needing a car), and there is something congenial and inviting about seeing a dog wag a tail inside a tram car.  The tramway dropped us in front of a gelato shop, so we indulged (yes, I could get used to this).

Among the customers was a lady getting a gelato for her little boy.  She spoke to him in a thick British accent.  We struck a conversation; yes, she does live in one of these apartment blocks.  They are recent arrivals from London; her husband had been promised a spot on a football team, but that fell through.  She managed to find work at a call centre, one of the few options for someone with poor German. She mentioned that the relatively low rent is one of the attractions of the neighborhood.  I mentioned that the buildings are supposed to be energy-efficient; she agreed (it makes for low monthly bills), but snickered a bit when she mentioned that renting families are given a whole sheaf of instructions (how to set up the thermostat, when to open the windows, put down the blinds, etc.).  She didn’t explicitly say it, but her smile seemed to say “Germans!  They have rules for everything!”  She said they were very happy living there; it’s convenient, quiet, and safe – including from traffic when her son plays outside.

A street in Kronsberg

We went around for a walk, discovering the neighborhood.  Lots of green space, and some green space where you don’t expect it: on the roofs.  Turns out that some of the row-houses are all built above the required energy efficiency standard for the development: they are all PassivHaus, with a green roof to boot.  This was rather daring back in the 90s; but it’s thanks to these pilot projects that such standards are now commonplace.  The green roofs – grass on sloping roof – not so much, but they’re fun.

We saw kids playing in an un-mowed, tall grass common.  This is often a big no-no in our cities (egad, this is where perverts and coyotes lurk!) but it reminded me of my own childhood, playing in the neighborhood “bush”, the vacant land by the railroad tracks.  Sure enough, these kids seemed pretty happy – and safe.

We walked around into what looked like a fancier part of the neighborhood, a row of neat two-story houses, with small yards.  Between the sidewalk and the street was a shallow ditch, with little concrete weirs at regular intervals.  Everything looked very tidy.  It was pretty quiet (this was the middle of a work day) but we did meet somebody puttering in front of a house.

It was a middle-aged man doing a bit of landscaping.  Yes, he lived there, this was his house.  He said that the houses and townhouses here were pretty much all resident owned; the low-rise apartment blocks, next street, rented.  He said that there was an interesting mix of people in the neighborhood, including many immigrants, but everybody gets along; it wasn’t an issue.  I asked about the drainage ditches in front of the house, are they a problem?  He said not at all; the city looks after the ditches and the other drainage features, and they do a good job of maintenance.

A Mulden-Rigolen runoff control swale

Those ditches, I learned later, are part of a system called Rigolen-Mulden.  They are quite shallow, and catch whatever runoff the streets produce.  The water ponds behind the little weirs during a rainstorm; the depth is shallow, but with so many weirs, there is considerable storage.  Any excess goes into the storm drain, but most of it does infiltrate to the groundwater; indeed, below every ditch (or swale, to use the right term) is a layer of crushed stone that provides room for storm water.  The proof is the pudding: a study showed that there is barely any more runoff now than before development (only about 3% of the rain ends up in the storm drains – an ordinary development usually generates ten times more).

One also notices an absence of graffiti.  On its website, the city boasts of great social integration in Kronsberg, of a “broad social mix for the district”.  They may be on to something, indeed.  This is a place where a third of the residents are immigrants, a quarter are teenagers or kids.  One tenth of the housing stock is social housing, and half of the rents are subsidized.  Maybe this is what is needed.

When Kronsberg was planned, the city had a unique advantage: it owned the land.  It was in position to impose strict demands on the private developers; they had to ensure that all the buildings were energy efficient (a maximum of 50 kWh/m2 for heating).  This was meticulously measured after completion, and developers knew they were going to be fined if they didn’t meet the targets.  As a result, the buildings are actually under the target.

What didn’t work was the planned reduction in electricity consumption.  The plan was to provide generous grants for energy efficient appliances and fixtures; but residents generally didn’t take advantage of these (most preferred to move their old ones rather than shell out for new ones).  The actual electricity use reduction (6%) fell far short of the ambitious 30% reduction target.

There were also some special projects piloted in Kronsberg.  One of these is a thermal energy seasonal storage system: a large cistern stores water solar heated during the summer, uses it during the cold season.  This provides 40% of the heating needs of 104 apartments, similar to another development in Hamburg that I described earlier; the key difference is that Hamburg’s uses hot air instead of hot water, but the performance is similar (and the energy storage takes room, making it more appropriate for a suburban environment).

The green-roofed PassivHaus rowhouses

There was also a series of 32 PassivHaus rowhouses.  PassivHaus standards (a maximum of 15 kWh/m2 for heating) were fairly new at the time, and combining them with green roofs was considered daring.  But it has withstood the test of time nicely, which is all the more remarkable since these apartments are all subsidized rentals.

Another way to tell that the project was successful: it was copied.  Hanover has launched another neighborhood development, called the Zero:e park, built roughly along the same lines.  Like Kronsberg, it is also built on former farmland (26 hectares) at the edge of the city, row houses and detached houses, all built according to zero-carbon guidelines, optimized for solar energy capture.  There is even a supermarket (a REWE) built to PassivHaus standards, using the waste heat from its food refrigerators to heat the building, a first.  This would not have happened if Kronsberg hadn’t showed the way.

Meanwhile, Kronsberg made me rethink my opinion of suburbia.  Yes, I still hate car-dependent sprawl.  And building on farm land is not appropriate everywhere.  But the combination of rail-based commuting, energy efficiency, and affordability is pretty hard not to like.

In my journal notes from two years ago, I wrote “all shopping amenities are near tram stops, and we thought that this style of living in the burbs was definitely great (imagine transporting this to Surrey!).”  Yes, indeed.  Imagine!


By the numbers:

3200 units on 70 ha (ultimate number 6000), 45 units/ha

Green space 64%, open water 2%, 0.8 parking spot per unit

Three tramway stops (maximum walking 600 m), ratio of jobs per unit: 67% within 0.8 km radius  

Energy supply: 2 CHP plants, 2 MW thermal and 1.5 MW electric together

Peak heating load provided by gas boilers 11.6 MW

Seasonal solar storage: 1350 m2 flat plate hot water, 2750 m3 storage cistern, 40% of heating needs for 104 apartments

Three wind turbines: 0.28, 1.5, & 1.8 MW; with 45 kW photovoltaic, 72% of electricity supply

60% reduction in CO2 emissions

Mulden-Rigolen system: 11 km of swales, on every street.  Design objective: 3 liter/sec per ha max.   Water balance: 3% runoff, 50% infiltration, 47% evaporation.  Pre-development: 2% runoff, 45% infiltration, 53% evap.  (Conventional: 29% runoff, 25% infiltration, 46% evap) 

Much of that information is from Fraker, Harrison 2013. The hidden potential of sustainable neighbourhoods: lessons from low-carbon communities. Washington: Island Press. (An excellent book, where Vauban in Freiburg, B001 in Malmo, and Hammarby-Sjostad in Stockholm are also described and compared.)


Written by enviropaul

January 3, 2018 at 4:37 pm