Green roofs, green walls, green parking lots, shade trees, the greening of urban spaces in general, the restoration of urban waterways, wetlands and the re-greening of brownfield areas; can all be thought of as different techniques to nurture a green living skin (or at least a greener skin) over regions of urban development. While there are many important differences between each of these separate techniques as well as their underlying technologies they all share a common overarching goal of bringing an analog of the natural living green skin that characterizes the natural landscape back into our urban areas. They all promote the restoration and re-integration of these heavily populated areas back into the surrounding natural environment.

Promoting the use of green re-surfacing (such as green roofs or the planting of shade trees for example), fostering the expansion of urban green spaces and restoring often neglected and polluted waterways and wetlands to their natural state yields large benefits for water quality, lowered energy and potable water use. It also improves the livability of our cities and reduces their environmental footprint helping to mitigate large global problems such as climate change and water scarcity. Furthermore by reducing the environmental problems associated with the urban environment the green living skin can save lives, improve city dwellers health and save enormous amounts of money that would otherwise be spent on the chronic health problems caused by smog.

Besides the measurable and important benefits of lowered energy consumption, lowered peak energy consumption, reduced storm runoff, increased water quality, reduction in urban smog etc. there are many hard to quantify benefits for human well-being that derive from the aesthetic and psychological impact of a greener environment on a city’s population.

There is also an important health impact; heat waves are dramatic killers and as the global temperatures rise, these heat waves will become longer and more severe. Heat waves not only cause dramatically higher peak energy usage – taxing electric systems to their limits – they can lead to large spikes in serious health problems for vulnerable people in affected areas and have been responsible for thousands of heat related deaths.

Cities that have a Living Skin Are Better Suited to Survive Global Warming

Greener cities will be more adapted to survive the hotter extremes that climate change is guaranteeing they will experience. And furthermore greener cities that are protected by a green living skin will contribute far less to global warming than barren concrete jungles do, both because the green living skin is also a carbon sink and because by saving energy overall and by saving even larger amounts of peak demand energy they will produce much less CO2 than cities that do not embrace this ethic.

Killer heat waves, such as the killer heat wave that struck much of Europe in 2003 and that caused an estimated 70,000 heat-related deaths are going to become increasingly common throughout the world as the long term effects of global warming become ever more pronounced. Cities that protect themselves with a green living skin will fare much better in these extreme weather events than those that do not.

The Urban Heat Island is an Energy Hog

As urban areas have spread out to cover vast regions they have begun to create their own weather. The vast expanses of concrete and asphalt have lead to what is known as the urban heat island effect. Big urban areas average around 3°F warmer than surrounding vegetated rural areas; this effect can rise to higher levels during summer heat waves

A Lawrence Berkeley National Laboratory study for the DOE (Department of Energy) “Energy Saving Potentials and Air Quality Benefits of Urban Heat Island Mitigation” has found that in the United States this increase in air temperature is responsible for 5–10% of urban peak electric demand for a/c use, and as much as 20% of population-weighted smog concentrations in urban areas.

The study ran a computer simulation for the L.A. basin and found that “resurfacing about two-third of the pavements and rooftops with reflective surfaces and planting three trees per house can cool down LA by an average of 2–3K (degrees Kelvin equivalent to 3.6-5.4 °F). This reduction in air temperature will reduce urban smog exposure in the LA basin by roughly the same amount as removing the basin entire on-road vehicle exhaust [my emphasis]. Heat island mitigation is an effective air pollution control strategy, more than paying for itself in cooling energy cost savings.”

This study focused on reflective re-surfacing that has the goal of increasing the albedo or reflectivity of a surface so that more heat is reflected back up into the air and less heat is absorbed. This is complimentary to green living skin re-surfacing and is applicable in areas where it is not feasible to apply a green living surface. For example on road surfaces, high use parking surfaces, or on roofs with a steep incline for example.

For an in depth look at green parking lots see our three part article series on the area of green parking lot design: Green Parking Lots: Part I – The Many Problems with Paving

Protecting our Cities with a Living Green Skin Could Reduce Health Care Costs and Save Lives

The dramatic reduction in urban smog that can be achieved by reducing the urban mean and peak temperatures will make cities much more livable and improve the long term health of city dwellers. Smog related health problems such as asthma, emphysema and chronic bronchitis can become sever in cities such as the L.A. basin and are an increasing problem almost everywhere. These smog related health issues are also very expensive.

The South Coast Air Quality Management District has this to say about the Los Angeles basin or South Coast Region, “A 1989 study funded by AQMD and conducted by Dr. Jane Hall of Cal State Fullerton found that meeting federal clean air standards for ozone and fine particulates in the South Coast region would provide $9.4 billion in health-related benefits each year. The study found that 98% of the four-county basin’s population of 13 million is exposed to unhealthful air, with children especially vulnerable. In addition, 1,600 people die prematurely as a result of exposure to air pollution, according to the study.”

That is an annual saving of almost $10 billion for just a single metro region! Re-surfacing and growing a living skin over the urban areas of the South Coast could be financed from the associated health care saving alone.

In addition to smog related health care problems the overall improvement in urban water quality and especially the significant reduction in the incidences of sewage overflow events will also lead to a better health environment and a reduction in associated health costs. Water pollution is a serious health issue in urban areas and polluted runoff creates a persistent health hazard and degrades the quality of water resources in the ground and in the surface waterways, wetlands and beaches.

How Green Roofs and Green Walls save Energy and Save Money

Promoting the greening of our urban landscape is not only aesthetically pleasing it yields significant economic benefits that directly impact the bottom line and can lower the on-going operating costs for buildings and other urban installations such as parking spaces. For example green roofs and green walls can lower the heating and cooling bills for buildings that incorporate them. During hot summer days a green roof (or sun-facing green wall) forms a buffer zone between the building and the blistering summer sun. By shading the underlying roof (or sun-facing wall), it prevents the building’s structural surfaces from heating up and increasing both the outdoor and indoor air temperatures.

Conversely during cold outdoor conditions prevailing during winter months and during the night hours of Spring and Fall the vegetative living matrix comprised of the bio-mass of the root systems and plant cover that is provided by the green roof or green wall provides an extra layer of insulation outside the structural skin of the building thereby reducing heat loss. The thermal mass of the green skin (roof or wall) also smoothes out the swings between daily minimum and maximum temperatures and this also contributes to over all improvements in the buildings thermal performance. During hard winter conditions when the biomass of a green roof freezes over its insulation value drops.

It is important to state that each single building site will present its own characteristic profile and that therefore energy savings will vary from site to site. But the savings can be very dramatic as was documented in a study by National Research Council of Canada, “Thermal Performance of Green Roofs through Field Evaluation.” This study has shown that green roofs can be very effective at reducing the heat transfer through a roof, thus saving energy. A reduced average daily energy demand of 75 percent test was documented in a test facility with a 400-square-foot green roof. Green roofs accomplish this dramatic reduction in the heat flow into the structures they protect through a combination of shading, insulation, evapotranspiration and thermal mass.

For an in depth analysis of sustainable building design and techniques see our four part article series on the subject: The Green (or Sustainable) Building: Part I – What Is the Green Building DNA?

Can we tame the Concrete Jungle with Urban Forests and Green Roofs?

Our world’s sprawling urban landscapes have been denuded stripped of their natural protective cover and turned into harsh unnatural environments that are susceptible to extreme temperatures and that gobble staggering amounts of energy and water to sustain themselves. The world’s urban areas – and especially the rich industrialized world’s urban areas – contribute a disproportionate share of the world’s global warming gases though their massive energy consumption. They also suck up massive quantities of potable water and because much of their surfaces are hard paved over contribute to polluted storm surge runoff, which taxes and increasingly overloads the surrounding water systems.

We have created these vast cement jungles with very few living surfaces left in their midst. Increasingly we are becoming aware that there is a growing cost associated with this type of urbanity; a cost that is becoming increasingly unsustainable.

Perhaps the time is ripe for a profound rethink and reset in our ideas and philosophic notions of the urban built over space, of our cities and towns; of what these population dense areas should be like and how they should be designed and retro-fitted.

One study estimated that each tree planted in an urban area saves $200 in energy savings alone. That same single tree also makes the spot it graces slightly more livable in many other ways; by providing shade, supporting wildlife, filtering the surrounding air, providing quiet (in fact trees absorb and diffuse sound), helping to mitigate strong winds and so forth. Just imagine what an entire urban forest can do. Just the simple act of planting trees along roadways and other available surfaces can help improve a cities thermal profile and create a much more livable environment in other ways.

Skeptics – who like to define themselves as realists – will speak about the costs of retro-fitting a city with a green living skin and may dismiss the whole idea of a new green urbanity as some kind of New Age fuzzy headed mysticism.

But it is precisely on hard measurable, quantifiable cost metrics that a green urban philosophy can be justified. The cost savings realized by reduced energy expenditures; the huge savings of both lives and annual reduced health costs that arise from the chronic (and very costly) health conditions associated with urban smog; the savings in the needed sewage treatment facilities and water usage. All of these are quantifiable and compelling arguments for adopting a green urban design philosophy.

The aesthetic improvements of the urban space, the fostering of urban habitat and an increased livability for all are icing on the cake. The justifications for taming the concrete jungle and greening our cities rests on solid ground and is becoming increasingly vital to the continued vitality of our cities and urban areas in a world of increasing temperatures and ever higher energy costs.

© 2009, Chris de Morsella. All rights reserved. Do not republish.

This, the second article in our three part series on green parking lots continues the discussion by looking at some of the green parking lot design techniques and materials and how they help make parking surfaces more environmentally friendly and improve the urban space most of us live in.

In case you missed the first article in our series it can be found at: Green Parking Lots: Part I – The Many Problems with Paving.

Before continuing with a discussion of the various design techniques and materials for building green parking lots it bears mentioning that the whole idea of parking lots itself and of the car culture that they are artifacts of is being called into question by many advocates of a new sustainable urbanity. Our current car centric urbanity is clearly unsustainable and ill suited for a future of increasingly expensive energy. The vast flat top parking lots and strip mall road facing lots that are in some way emblematic of the car cultures impact on the urban space may begin to shrink and even in many cases vanish as cities re-orient themselves away from the car and serving the car’s needs. Many, myself included argue that this will be inevitable driven by the inexorable decline in recoverable petroleum resources and with it the end of the age of easy energy.

However even without accepting this argument that the decline of our car centric culture is inevitable and imminent one can argue that in all too many instances parking areas are way over built and are built with each single space being too large. Reducing both the number of parking spaces and the average size of each single space is perhaps the single most important thing that can be done to make parking lots as green as they can be. These are techniques that apply to both multilevel parking facilities as well as open air parking facilities.

Another practice that can reduce the need for parking is to explore the possibility for shared parking arrangements could include usage of the same parking lot by different facilities that need it at different times. For example consider pairing an office space that experiences peak parking demand during the weekday with a church that experiences parking demands during the weekends and evenings.

Maybe Parking is a Case of Less Is More

In malls across the country parking areas are designed to have the capacity to accommodate maximum predicted traffic – such as occurs in the weeks leading up to the Christmas Holiday rush. In fact, look at just about any big mall anywhere, at any other time than the busiest days of the shopping year and you will see large sections of nearly empty lot, dotted with a lonely car or two. Is this over building really necessary and are there better ways to provide for overflow capacity than needlessly paving over vast areas of land with empty asphalt. A similar dynamic is at work at arena and event areas. Most of the time, the associated lots are mostly empty. For example a stadium or arena will often be somewhat empty during off season events or poorly attended regular season games; while on some occasions it will become packed to overflowing capacity.

For these types of situations if overflow parking is deemed necessary, for commercial or other reasons then at least it should be looked at differently and designed very differently from the much smaller core parking areas.

When it Comes to Parking Maybe Smaller Really Is Better

Another green parking lot technique is to minimize the dimensions of the parking spaces themselves in this manner squeezing more parking stalls into a given area. This can be accomplished by reducing both the length and width of the parking stall. Parking lot dimensions can be further reduced if a greater number of smaller compact spaces are provided. Not every vehicle is an SUV or oversized pickup truck and as the cost of gas continues its long term rise and concerns about greenhouse gas emissions grow more and more of the vehicles in the total mix of vehicles will be smaller compact cars.

It should be noted that parking stall size as well as the number of stalls required per unit of occupancy or square footage is often regulated by city codes and these codes themselves are need to evolve to better reflect the emerging green urban design that is our cities best hope at preserving their vitality and avoiding decay.

Preventing Stormwater Runoff Can Save Money

One of the principle ways open air parking lots can be made greener is by using permeable pavers instead of the impermeable surfaces, such as asphalt or concrete that is the current common practice. Consider replacing conventional asphalt or concrete in both new developments and redevelopment projects with alternate pavers. Using permeable paving surfaces helps to reduce storm water runoff by allowing rain to permeate the paving surface and to slowly become absorbed by the ground underneath where it is slowly filtered and released cleansed into the aquifers and water systems.

Preventing storm runoff is not only good for the environment, but can be good for the bottom line as well. An example is cited in the Land Development Today magazine, April, 2006 issue, for a 12 acre development project in Maryland with a 7 acre parking lot which initially was required to provide a 1.5 acre stormwater retention basin. Through the use of pervious concrete to absorb rainfall and manage stormwater, the need for the stormwater retention basin was completely eliminated saving the developer $400,000 relating to the cost of land and construction of the retention basin.

Cool Paving Fights the Urban Heat Island

Grass paving blocks, but also to some extent other permeable paving surfaces have the additional benefit of helping to mitigate the urban heat island effect. In summer asphalt especially can become as much as 50 to 90°F (27 to 50°C) hotter than the air. Choosing a cool paving material that is light colored and is permeable allowing for some air movement and evaporation through it can help fight this urban ill. Grass pavers are especially good for this because they further cool the ambient air through the process of evapotranspiration, in which the grass in this case releases water to the surrounding air that has been drawn up through its root system, dis¬sipating ambient heat. Even if grass pavers cannot be used for an entire lot using them in seldom used overflow parking areas can significantly reduce the parking lots overall contribution to the urban heat island.

Remember that demand for air conditioning increases by approximately 1.5-2% for each 1 degree (F) increase in summertime temperatures.

Alternate Pavers To the Rescue

Alternative pavers are permeable surfaces that can replace asphalt and concrete and can be used for driveways, parking lots, alleys and walkways. Alternate pavers can be broken down into three broad categories, which are: paving blocks, other surfaces and engineered porous pavement.

Grass or permeable pavers are interlocking concrete blocks or synthetic fibrous grids (usually a rigid plastic) with small open areas that allow grass to grow within the voids; sometimes these voids are filled with gravel instead. They provide a rigid surface able to support a vehicle weight while gravel or grass planted inside the holes allows for infiltration. Depending on the projected use and on soil types, a gravel or crushed rock layer can also be added underneath to prevent settling and allow for further infiltration.

Some examples of other non-block paving surfaces are: gravel, cobbles, paving stones, wood mulch, brick and natural stone. Brick and natural stone arranged in a loose configuration allow for some infiltration through the gaps and along with gravel and cobbles can be used as a driveway, alley way, or parking stall material. Wood and mulch can be used to provide walking trails.

The EPA defines Porous pavement as a permeable pavement surface – usually understood to be made of porous asphalt or pervious concrete. Most often porous pavement is engineered to have an underlying stone reservoir that can temporarily store surface runoff before it gradually infiltrates into the subsoil, thus allowing stormwater to infiltrate directly into the soil below and receive water quality treatment.

While porous asphalt and pervious concrete appear to be the same as traditional pavement, unlike traditional pavement, it contains little or no “fine” materials. Instead, it contains many micro voids that encourage infiltration. Porous asphalt pavement consists of an open-graded coarse aggregate, bonded together by asphalt cement, with sufficient interconnected voids to make it highly permeable to water. Pervious concrete typically consists of specially formulated mixtures of Portland cement, uniform, open-graded coarse aggregate, and water. Pervious concrete has enough void space to allow rapid percolation of liquids through the pavement.
Alternative pavers are not recommended for high-traffic volumes. Access for wheelchairs is limited with alternative pavers. In addition, snow removal is difficult since plows cannot be used, sand can cause the system to clog, and salt can be a potential pollutant. However even in regions that need regular plowing during the winter overflow areas on the far edges of parking lots can be constructed using alternate pavers and simply not be plowed. Snow piles can also be collected in these areas avoiding the need to remove it.

Next; How Landscaping Can Help

In the next and last post in this three part series we will examine the various landscaping techniques that can help make parking lots become much greener than they are. Look for: Green Parking Lots: Part III – How Landscaping Can Manage Runoff scheduled for publishing tomorrow.

© 2009, Chris de Morsella. All rights reserved. Do not republish.