CHAPTER 2, PART 1A: LITERATURE REVIEW (the scholarly stuff)

HISTORIC MASONRY RESTORATION BEST PRACTICES

Buildings fifty years of age or older with great architectural or cultural significance are generally referred to as “historic.”  These important pieces of history present many common issues for all parties involved in the rehabilitation process when planning rehabilitation projects, but with thoughtfully and appropriately designed restoration plans, the integrity of the existing masonry can be preserved, and the building can continue its life.

                “Historic masonry” includes brick, terra cotta, stone, concrete block, cast stone, and secondarily mortar.  Amy Lamb, P.E estimates in her article “Historic Masonry Best Practices” that mortar typically comprises 20-25% of a masonry wall system, and notes that masonry walls are great at compression but poor in tension unless they are reinforced. 

Figure 7

Figure 8, Mass wall at

the Malt Kiln

Mass masonry walls are a common type of historic masonry wall system, perhaps the oldest masonry wall typology (Figure 7).  These walls have proved to last thousands of years in some cases.  Mass walls are load bearing and act as the main structure of the building, even without reinforcement incorporated into the wall itself.  Generally, the height of a mass wall determines the width at the base, and typically as the wall rises up it narrows to alleviate weight from above.  As mass walls are made of solely porous materials, such as brick and mortar, they require continuous maintenance in order to effectively manage water.  This same porosity that allows water into the wall can also be beneficial in that it can allow residual water that enters the wall to dry out naturally on the exterior and interior sides of the walls through natural ventilation.

In the 1890’s, mass masonry walls became an ineffective building solution as people wanted taller buildings with the use of elevators becoming more common.  Mass masonry walls were very thick and limited available interior space, and to achieve structural integrity they had little space for window openings limiting natural light and ventilation.  The solution was to integrate steel “skeleton” structures into the building design, which allowed walls to be thinner and more windows to be placed. 

           When approaching the rehabilitation of mass masonry walls, it is important to begin by gathering all available background information regarding construction, repair, and maintenance history.  If available, original building drawings should be carefully reviewed and compared to visible existing conditions.  Other helpful sources of information can be the building owners and maintenance workers.  Once this information is obtained and reviewed, the building should be visually inspected and observations should be noted, especially damage or deterioration at horizontal surfaces and cracks in the facades.  Tools such as a rubber mallet can be used for “sounding” to detect hidden defects, along with smaller poking and prodding tools.  This type of investigation may also include exploratory openings by a qualified masonry restoration contractor in order to prevent surprises during construction.  Field and laboratory testing can be performed to determine the root cause of deterioration and can be non-destructive (ultrasonic testing) or destructive (flat-jack [Figure 9], water, or adhesion testing).  Laboratory testing should be done to determine the composition of materials in order to understand their current integrity and to ensure new materials will not cause further deterioration.

Figure 9

            Water infiltration is one of the most common causes of deterioration for mass brick walls as they rarely included water management in their design.  When water infiltrates the masonry, it can freeze and expand leading to cracking leading to the structural integrity becoming compromised.  The cracking, spalling, and scaling caused by freezing opens the walls to more opportunities for water to infiltrate, leading to further damage.  As water is more likely to infiltrate at horizontal surfaces, the most vulnerable areas to water damage are usually parapets, cornices, and windowsills. 

            With all the research and information gathered, the restoration work can begin, but not before temporary stabilization is installed as needed for potential hazards.  With stabilization in place, the first step of the work should include protection of horizontal surfaces with various measures including sealant and backer-rood installation, protective silicone sheets, sheet metal installation at joints, and reinforced liquid roof membrane applied at horizontal surfaces of ornamentation and the roof.  Next, any corroded steel elements should be replaced, repaired, or coated, which can be done by carefully removing existing masonry to access such steel elements, performing the repairs, then reinstalling the masonry in place.  The same method can be used to install new flashing as needed.  Masonry anchors should be installed as needed to provide lateral support to the existing walls.

                When beginning repairs on the masonry and mortar, the previously done testing should determine what new products are used in the repairs or replacements so that they match the properties of the old materials such as strength, density, water absorption, and vapor transmission.  Replacement bricks should also attempt to match the clay, aggregate, and cementitious components of the original so that the new materials either match or have weaker characteristics than the original as modern materials are often more finely processed therefore denser and stronger than historic materials.

RUINS

            The idea that redundant buildings are often redundant because their original use is no longer viable is taking root across the globe, however finding support for projects involving ruinous buildings is harder than finding funds to demolish and build new.  The Roman Forum is one of the most famous ruins in the world, and coincidentally has a long history of being reused and adapted in various ways over the centuries.  For ruins less highly regarded as the Roman Forum, it is often tough to find organizations to fund the continual maintenance and the associated large costs to ensure visitors can wander around "huge lumps of masonry", but even tougher when ruins are privately owned as the financial burden falls solely on the owner.  Generally, buildings that have beneficial uses are valuable to society and are more likely to be rehabilitated and survive than buildings that have no use at all.

In “New Life for Old Ruins,” Michael Davies notes three specific issues that should be the primary considerations when planning adaptations to Ruins:

First, how will the visual impact of the new structure relate to the old?  Additions and adaptations to ruins can be built inside the ruins (1), on top of the ruins (2), or around the ruins (3) as demonstrated in Figure 10.  Building inside the ruins tends to express the ruins best, while building on top of the ruin allows the ruin to be seen from both sides of its walls.  Building around the ruin is often the simplest and least destructive solution, enclosing the ruin and protecting it from the elements.

Figure 10

Second, the choice of materials and design style will significantly impact the ruins.  The approach of trying to match a new addition to the existing ruins is often unsuccessful in many ways, mostly because it distracts from the ruins themselves and makes it difficult to tell where the ruins end and the new building begin.  Davies suggests approaches that either introduce a "seam" of clear delineation between old and new such as a line of colored stones or following a more widely favored approach of designing an addition to have a clear contrast between old and new.  The contrasting addition accentuates the historic ruins and makes them stand out against a modern surrounding. 

Third, the challenges presented by the materials of the ruins cannot be addressed with traditional construction methods.  Historic stone and masonry often have irregular edges making it difficult to install new materials on their surfaces.  It is difficult to make existing openings airtight for the same reasons.  Davies notes that in some cases, concrete or stone can be installed directly at the tops of ruinous walls where irregular edges exist in order to provide a smooth and level surface for new building elements, such as at Norwich Refectory in the UK.  A common dilemma faced in projects of this type is deciding if all stones are so precious that they should remain in place, or if removing a few strategically would have greater benefit to the project.  Davies notes that "managing change is all about compromise.  Bringing new life to a ruin has obvious benefits, but these must be balanced against the loss of a ruin as a piece of architectural sculpture that is in a state of ongoing organic decay, and the loss of something that appeals to our artistic and romantic sensibilities."

Figure 11, Norwich Refectory (Norwich, UK)

INSULATION RETROFITS

            Due to rising concerns with energy consumption, reducing the energy consumption of the built environment has become imperative to society.  Modern research and technology have provided many options for achieving lower energy usage in buildings, but many buildings today, especially historic ones, exist without any energy saving interventions.  It would seem that an easy solution to reduce energy consumption in historic mass brick buildings would be to insulate the brick walls on the interior, allowing a reduction in energy used for heating and cooling.  However, in climates with cold and/or wet weather, this insulation can end up causing more harm than good.  As mass brick walls are able to utilize natural ventilation on both sides of the wall to dry themselves from water that may have infiltrated them, adding insulation to one side can prevent the interior side from fully drying leading to mold and deterioration. 

                When adding interior insulation on brick mass walls, the temperature gradient of the masonry is lowered, reducing the difference in temperature between the masonry and the exterior air.  This reduces diffusion drying capacity throughout the masonry and causes surface evaporation to be slowed, together reducing the overall drying capacity of the masonry (Figure 12). 

Figure 12

                It can be assumed that common moderate density brickwork provides an R-value between R0.25 to R0.33 per inch, with a three with (12”) brick wall providing an R-value between three and four, plus surface heat transfer coefficients (“air films”) of another R1.  Aside from deciding whether or not to add insulation to the interior, assessments of the windows, roofs, and airtightness must also be made.  Major performance improvements to these items can significantly impact the overall building performance, leading to a reduction in energy consumption in addition to improved comfort.

SPOLIA

“Spolia” is the Latin term for “spoils,” typically interpreted as “spoils of war.”  Since the sixteenth century, this term has been applied to the realm of art and architecture to describe reused ornamentation and elements.  This term carried some negative connotations, as if implying that these elements were forcibly removed in order to be used as a display of honor.  The use of spolia began at the decline of ancient Rome and continued through the Middle Ages, then died during the Italian Renaissance.  Considering this history, Dale Kinney describes spolia as something that “just happened” and was accepted as architectural tradition.  While this tradition held different meaning in medieval times, modern architecture has transformed it to meet modern tastes.  We have moved from using spolia out of tradition to using it for environmental purposes.  (Kinney, D. 2001)

WINDOWS

Walter Sedovic and Jill Gotthelf begin their essay, “What Replacement Windows Can’t Replace:  The Real Cost of Removing Historic Windows,” by pointing out the fact that many modern window manufacturers advertise that replacing old windows is the first order of business in restoring old buildings.  The authors argue that this approach be reconsidered and emphasize many benefits of restoring original windows instead of replacing them with replicas.

The first point Sedovic and Gotthelf make is that historic windows are authentic, and authenticity is crucial to any historic preservation project.  Next, restoration is more labor intensive which provides a boost to the local economy through job creation.  Additionally, as historic windows are typically operable, they can provide natural ventilation leading to a reduction in size of mechanical equipment.  Reusing and/or restoring historic windows promotes sustainability through preserving embodied energy from their original manufacturing process, reducing the need for new resources and minimizing pollution associated with new window production.  Historic windows are generally framed with wood, but historic wood is often much more durable than modern wood due to the methods currently used for growing lumber forests. 

While air leakage and interior comfort can be a concern when keeping historic windows, there are steps that can be taken to minimize these negative effects.   Window film or tinting can be applied to old glass to reduce solar radiation inside the building.   Weatherproofing can be installed to combat air leakage.  With a combination of these two methods, historic windows can often be improved so that they meet or exceed the performance of modern windows.

Although not as impactful as conserving the environment or saving on energy costs, there is something to be said for keeping a historic building’s aesthetic and authenticity.   Small details like replacement windows can have a big impact on the overall look of a historic building.  Sedovic and Gotthelf state that based on their field experience, restoring a historic window is on par cost-wise with a “middle of the road” replacement window.  They further state that “cheap replacement windows will always exist to superficially counter the cost-basis argument for restoration; and high-quality equivalent replacement units have been shown in practice to cost as much as three times that of restoration.”   Considering all of this information, it would seem that in the context of historic preservation projects that some level of window restoration makes a lot more sense than full replacement.  (Sedovic, W., & Gotthelf, J. H. 2005)

BRICK

The use of reclaimed brick is not a new trend.  It has seen popularity at various points in modern history and seems to be “on trend” today.  An obvious benefit of using reclaimed brick in new construction is that it is more environmentally friendly than using newly manufactured brick, but this option also comes with a certain aesthetic that the general population enjoys. Reclaimed bricks are often chosen for their character, which cannot be matched by modern brick-makers.  The use of reclaimed bricks helps prevent mining of clay; a natural resource that is quickly being depleted.  Even knowing this, most of the time reclaimed brick is chosen because it offers certain colors, texture, and even romantic charm that new brick simply does not have.

If they cannot be reclaimed and reused, old bricks can easily be recycled into new bricks, and these new bricks can be just as strong as traditional bricks.  COWI, a Danish engineering, environmental, and socioeconomic consulting firm, came up with an idea to help make a housing project “greener” by using recycled bricks.  These bricks are 95% crushed recycled brick, and 5% mortar granules added for bonding.  This process does not require extreme heat, as the bricks are formed at room temperature in molding machines using vibrations and high pressure.  Using this method, fifteen bricks can be made using the same amount of energy that it takes to make one traditional brick.  They also cost 10% less than traditional bricks to manufacture.  This method is a great alternative to using reclaimed brick in its original form if it cannot be safely reused since it still makes use of what would otherwise be thrown in a landfill and offers reductions in the energy and emissions that result from producing traditional new bricks.  (Weinhold, B. 2003)

EMBODIED ENERGY

It is obvious that reusing salvaged materials is a great approach to bettering the environment, but in order to understand exactly what this means we need to dive a bit deeper.  Looking at the concept of embodied energy, it is apparent that the reuse of materials conserves much more than just the energy required to manufacture the material.  Reuse of materials saves energy from the initial raw material extraction, the processing of raw materials, and any transportation required, all of which have negative impacts on the environment.  In 1976, a report was compiled that detailed the embodied energy required for specific building types and typical building materials.  While this information is likely outdated now, it is considered the most thorough evaluation of embodied energy of building materials in the US and has been used as the basis for all future studies of embodied energy in construction.  It can be assumed that for many of the materials studied that the required embodied energy today is slightly less than it was at the time the report was written since manufacturing processes and technology have greatly improved.  The same report provided a breakdown of how embodied energy is distributed throughout the entire construction process, and it is particularly interesting to see that it is estimated that 50% of required embodied energy comes from the manufacturing of the basic architectural materials and components.  (Jackson, M. 2005)

DECONSTRUCTION

“Deconstruction” is a term that simply means “construction in reverse.”   Demolition results in a large pile of debris from which some items can be picked out for recycling, but deconstruction is the careful disassembling of an existing building that results in usable salvage material.  Deconstruction can pose many hazards to workers, but it provides many more benefits such as less impact to the environment from re-using building elements and due to the labor-intensive nature, it can provide more local jobs. 

This is not a new process. In fact, we know that in the Roman Empire, Roman engineers would reuse stones from old roads to build new ones.  This concept was widely used for centuries, but with the availability and easy access to landfills today, it has fallen out of fashion as demolition is easier and cheaper. 

With today’s ease of access to landfills they are filling up at alarming rates, and with tighter environmental restrictions in place for new landfill sites it is becoming harder to start new ones.  Dumping fees have increased dramatically in recent years, adding sometimes significant cost to the “easy” option of straight demolition.  Interestingly, at the same time the value of salvaged architectural elements have been increasing, such as flooring, old bricks, and mantels.  These types of historic items are not available new today, and the quality of these historic elements greatly surpasses any new replicas.  There are many organizations that take donations of architectural elements and either sell them to the public or donate them to other organizations that use them in charity projects.

By going the route of deconstruction, it is also easier to separate materials for recycling. It is estimated today that there are over 3,100 concrete and asphalt recycling plants, about six hundred single-material or mixed-waste recycling facilities, and several dozen each of asphalt shingle and gypsum recyclers.  Many local governments have passed ordinances requiring that certain percentages of construction waste must be recycled, which is a step in the right direction for environmental conservation.  Concrete can be recycled into aggregate to be used as the base for new roads and parking lots, and crushing and grinding machinery has been made portable so you can even do this on-site.  Wood can be diverted from landfills by being used as boiler fuel at the bare minimum, but with the use of tools like pneumatic denailers and machines to strip lead-based paint, wood in good condition can often be reused for its original purpose as framing, flooring, or siding.  Scrap metals (iron, steel, copper, and aluminum) can be recycled at mills that melt it down and turn it into new materials for construction. 

It is easy to see that salvaging materials from old buildings being taken down is a good thing.  Unfortunately, the process of doing this often requires significant attention to safety for the workers which can be a deterrent for project leaders.  However, the required safety measures are fairly reasonable and manageable.  Since workers are face to face with potentially hazardous materials like lead paint or asbestos, it is important to assess the building before the work begins as well as continuously during the deconstruction process to ensure hazards are approached in the safest manner possible.  If asbestos or lead paint are discovered, specialists must be hired to perform the removal.  Workers must also be aware of what they are removing and any potential risks for when elements are detached from the building, and they must be able to easily maneuver these elements outside to a designated area. 

By taking a “deconstruction” approach, materials can not only be diverted from landfills, but it reduces the demand for raw materials like wood and iron ore, in turn benefiting the environment.  With lower demand for these raw materials, the result is also lower embodied energy required for new materials. It is estimated that reusing building materials can save 95% of embodied energy that would otherwise be wasted.  Because hazardous materials are required to be disposed of in particular manners, when these types of materials are encountered it would seem that there is not an advantage to deconstruction versus demolition, but it has to be considered that it is unlikely that these are the only materials in a building being taken apart, so there is almost certainly at least some benefit to deconstruction.  (Manuel, J. S. 2003)

CONSERVATION AS PRESERVATION OR AS HERITAGE

“The preservation movement…is a rescue operation heroically and unselfishly salvaging some small portion of the architectural riches which were, and still are, being destroyed at an alarming rate.”

Figure 13

Figure 13 - Graphic depicting the past as it is transformed into heritage

In his essay, G. J. Ashworth breaks down conservation of the built environment into two categories: preservation and heritage.  These are two approaches to what we typically think of as historic preservation, and while different in many ways, they share many similarities.  Ashworth is defining the preservation approach as preserving the past simply because we can, and the heritage approach involves a more thoughtful approach of selecting specific things to conserve.  Figure 13 shows the past as what has happened historically, which is filtered through the selective memories of people, and the end result is typically considered heritage. 

Both methods of conservation are good, but Ashworth calls into question the end goals. With the preservation method of preserving for preservation’s sake, the end result is a never-ending list of monuments and buildings that should be conserved.  Preservation of historic buildings is not free nor easy, so this never-ending list becomes a burden to those responsible.  By taking the “heritage” approach, it is easier to define which buildings and monuments are actually valuable as part of a heritage.  With this approach, it can be decided which buildings and monuments have a history that is worth preserving in the eyes of the public.  With the heritage approach, it is also possible that the conserved building will be turned into a commodity to satisfy certain markets, and there is a fine line between keeping it historically accurate and creating a narrative loosely based on the true history, but on what side of that line the end result lands is up to those in charge of restoration.  (Ashworth, G.J. 1997)

“From the viewpoint of the user, authenticity lies in the nature of the experience not the object. Ultimately, then, authenticity is what and where we experience it, and is the nature and motives of the ‘we’ in these contexts that are worth investigating.”

“The past that now exists – whether through preservation or heritage planning – is a phenomenon that has been created and shaped by a series of intervention decisions – whether made consciously with this end in mind or not.” 

HISTORIC PRESERVATION AND SUSTAINABLE COMMUNITY DEVELOPMENT

“The traditional ideals of historic preservation focus on saving materials and structures that would otherwise be thrown away or demolished and are easily adaptable to contemporary, environmentally aware endeavors.”

Modern preservationists have taken note of this connection and are implementing plans and technology around the philosophies of historic preservation and environmental sustainability.  This makes a lot of sense - historic preservation does not have to be simply preserving the whole building or monument - it can be preserving parts of it, while still having a great impact.  Today, community developers are starting to take note of this connection between historic preservation and the environment and are restoring old buildings and implementing sustainable technology to create eco-friendly, more affordable environments. A main contributor to the aspect of affordability is that refurbished/recycled materials are often less expensive to purchase than new.

Ellis points out that many community developers have put a focus on incorporating historic preservation into their work, because this principle is easily integrated into community development focused on building infrastructure and morale.  By incorporating historic preservation into communities, these developers give the communities something unique to celebrate.  In developing areas, having something to celebrate can contribute to overall community morale which is something successful communities need to blossom.

In their article, Ellis discusses this phenomenon in a few different cities, one being North Saint Louis.  After WWII, Saint Louis became overcrowded, leading to great racial disparities and geographic segregation.  Many efforts were made to ease these issues, but none were quite successful.  An area called “The New Northside” is an area that has been working to overcome these issues. It is a community with many wonderful historic buildings, that unfortunately were not being well-cared for.  Today, however, it has evolved into a vibrant community focusing on sustainability, cultural exposure, and equity.  Many of the original structures in the area remain standing, and historic preservationists have incorporated many of the wishes of the community into these structures as they are restored.  As a result, the community has seen substantial growth in career opportunities, youth engagement, and neighborhood resources.  One of the keys to this success was careful planning by community and city officials.  (Ellis, S. P. 2019)

HISTORIC SITES

Throughout history, there is a pattern of buildings becoming abandoned and dilapidated before being saved by historic preservation efforts.  Each site that becomes restored to its former glory is done with different goals and intentions, and the way these restored sites are managed differs from site to site.  While these sites were saved by the historic preservation movement, they are rarely preserved, instead they are restored.  To preserve something suggests it will live on in its current state, but to restore means it is made to look like it did in a past time.  Oftentimes, these efforts over the last several decades have the public convinced that these preservationists are magic - able to bring something back from the dead, with little to no information.  What people do not realize is that oftentimes these restored or “preserved” buildings are not as accurately restored as they are made out to be.  Many times, the line between “preserved,” “restored,” and “reconstructed” are so blurred that these marvelous feats are simply accepted by all who visit as true to history.

These buildings are typically nothing more than a product of their times or an “interpretation” of the past, as they were restored with certain intentions.  Colonial Williamsburg, for example, is more of an expression of the American perception of the past in the 1930s than it is an accurate historical representation. Unfortunately, this particular “preservation” project set a lot of precedents for future historic preservation projects across the country, and not necessarily in good ways.

In his 1932 article titled “Everyman his own historian,” Carl Becker states that there exists not one history of past events but two: the first being what actually happened, and the second being what we think occurred.  This important distinction is often not considered with historic preservation projects.  Therefore, it is important that historic preservation does not feed humanity’s thirst for nostalgia, but instead strives for absolute historical accuracy and truth. (Pitcaithley, D. T. 1987)

VERTICAL FARMING

It is estimated that 90% of all the Earth’s fresh water is used in agriculture, which is an alarming percentage when you consider that a lot of this water is used once then discarded. Of this 90%, only a small fraction actually gets absorbed by the soil.  The rest is wasted due to exposure to pesticides, herbicides, and fertilizer.  This is not the only risk of contamination in agriculture - close proximity of agricultural farms to livestock farms has led to E-coli outbreaks on certain crops in the last few decades. 

Dickson Dispommier moved out of the medical ecology field and into vertical farming due to his interest in parasites and how to prevent them from contaminating our food sources. He states that vertical farming rose out of a need for food security and food production, the need to address both safely and without contamination. Dispommier had the realization in 2001 that if we are living vertically in major cities, why can’t we produce food vertically?  Thus the idea was born.  While cities may not be thought of as clean places, working in controlled indoor environments allows for greater protections against contaminants in crops.

Dispommier believes that anything can be grown successfully indoors, as long as the grower is willing to provide the correct environment for the crop.  This would mean it is possible to exceed consumers’ demands in terms of variety.  Plants can be grown hydroponically or in substrate, meaning even things like root vegetables can be successful.  (Platt, Peter.  2007)

FARMERS’ MARKETS AND FOOD DESERTS?

Farmers’ Markets offer a good alternative to shopping at grocery stores, especially when offered in areas where grocery stores are not plentiful.  While this seems like it could help alleviate many food access issues in food desert areas, it has been shown that the lower income populations do not participate in these farmers’ markets as they tend to be more focused on communities considered middle class.  Several studies, including one by Kantor in 2001, have shown that less than 25% of the population receiving food stamps participate in farmers’ markets.  Another study by Conrey et. al in 2003 observed that there was less than 70% participation in WIC redemption at participating farmers’ markets. It has been suggested that the three keys to improving the success of the WIC Farmers’ Market Nutrition Program (FMNP) are education, access to markets, and market quality. 

In 2010, it was observed in Washington state that farmers’ markets inside of food deserts saw double the amount of food stamps and WIC FMNP redemption as the markets outside of food deserts.  While this means that these programs are being utilized and can be assumed as being helpful, farmers’ markets in food desert areas in Washington only represent 8% of total farmers’ markets in the state.  If this number could be increased, perhaps more of the population in need would be able to benefit.

Improving access to food in areas considered to be food deserts has several facets.

Distances that are easily traveled by car are often not so easy by foot, especially when talking about a trip to the grocery store; and much of the population living in food deserts do not have access to a car.  By organizing farmers’ markets to be within comfortably walkable distances for populations in food deserts, it becomes less of a hardship for the target population to actually benefit from these markets.  The physical location of the markets is not the only barrier for those in food deserts, as they typically are lower income. Food offered at farmers’ markets intended to help food desert areas should also be priced in a way that it still can allow a profit for the farmers but also be affordable for those who need it most.  (Sage, J. L., McCracken, V. A., & Sage, R. A. 2013)

BUILT SYSTEMS, BIOMIMICRY AND URBAN FOOD-GROWING

“Even agriculture at its most non-invasive, ...is still modified, so in a sense ‘built’ by us.” 

Is urban food growing viable?  It is with technology, and it has proven to be successful. It is typically thought that a major hurdle to overcome is the cost of the energy required, but with today’s LED lighting technology, this may not be the case.  Robert Biel suggests that one of the greater issues to overcome is the growing medium chosen.  He calls into question the long-term viability of artificial growing medium, particularly that of non-soil types.  While hydroponics is a popular option, Biel believes that it goes against the notion of soil as a complex system that works together with plants.  Perhaps a larger issue to overcome in urban gardening is to eliminate risk and unpredictability, which can be hard to do because each urban farm has different physical conditions, different access to resources, different growing setups, different caretakers, and the list could go on.

Biel goes on to suggest that perhaps urban food growers should network with each other, so they can plan for crop production in order to minimize competition.  This would mean that different urban farms focus on growing different things in abundance and growing them well, so that when the produce is brought to sale, the people buying have access to affordable products that are good quality.  As a result, farmers markets will become more appealing to low-income people. (Biel, R. 2016)