Design and Innovation
A building which adapts, which is used intensely, is one which changes over time, and thus survives beautifully under a variety of conditions and pressures applied. It is one whose appeal is long lasting.
Our proposal is for a mixed-use building in the heart of Old North St. Louis – a once vibrant, public centered community which has diminished significantly under the weight of de-industrialization, suburbanization, and the ensuing decay of the inner-city. It is our goal to create a work of architecture that acknowledges this community’s vibrant past, learns from it, and seeks to replicate its scale and rhythm in a contemporary manner. The proposal seeks to achieve both a near-net-zero energy balance as well as a carbon neutral footprint.
A careful analysis of the neighborhood found that a standard module – both in width and height – existed and was repeated along the commercial corridor in which the project is aligned upon. As the neighborhood has redeveloped and re-invented itself, it has done so within this existing infrastructure – existing buildings which are commonly over a century old. This module, along with important qualities such an open plan and durable construction assemblies, has allowed for this redevelopment as it has proved widely accommodative to a multitude of layouts and programs. Much can be learned from a place which was developed and built in a time before the prolific use of fossil fuels and the transition of the city to the current neo-liberal condition, and this project attempts to leverage these lessons – along with technological innovation and intelligent design thinking – to create a work which is inherently and holistically sustainable.
Over the past three decades, Old North St. Louis as a community has been left largely vacant, but there is currently a strong revitalization effort taking place which seeks to restore the neighborhood to a past vibrancy. Our goal has been to learn from this past in a way that acknowledges the congruence between activity and density in the historic design of storefronts and row houses, and seeks to continue their latent scale and rhythm as a means of promoting a notion of community sustainability. The project does not seek to compete with what exists and what might become, but rather it desires to form a relationship with the built and the natural that fosters a healthier, more publicly oriented community.
As part of the revitalization work of the community development authority, a community garden has been operating within our site directly adjacent to the building as proposed. The building orientation, program, and fenestration all react in such a way as to facilitate a mutually beneficial relationship between it and the existing garden.
Adaptive comfort strategies, operable elements, bicycle storage, recycling rooms, and other elements encourage the occupants to become active users of a passive building, and are part of broader community sustainability strategies which educate citizens on the potentials for living sustainably and the nature of urban habitat. The current walkscore is 66.
Land Use and Site Ecology
The project sits directly adjacent to an existing community garden, and within the runoff watershed of the Mississippi River; it also exists within an urban habitat characterized by hardscapes and poor stormwater management practices. Through the use of a green roof, stormwater and greywater recycling, drip irrigation, and solar hot water, the project seeks to minimize water requirements, treat all water on-site, and eliminate runoff off-site.
The building’s first level consists of a grocery store and a café. This program was chosen – in part – because of the existing presence of food production on-site, and the desire to create a synergy between the building and this resource. This mutually beneficial relationship will help to satisfy the current need for access to fresh, healthy food as the neighborhood currently exists within a designated food desert. Beyond satisfying this need, it will also facilitate the operation of community supported agriculture (CSA) on-site.
The neighborhood grid is rotated twenty-one degrees west of cardinal north. This, along with the restrictions of current and future developments on solar access, and the contextual need to prioritize the street façade, makes an optimal solar orientation impossible. To overcome this challenge, the building is partitioned into multiple zones. The southern half of the building at the commercial level has a higher glazing ratio and in-turn, takes advantages of passive solar heat gains during heating months. The northern half – containing higher internal heat loads – has a lower glazing ratio and relies upon higher insulation values to minimize exchange through the envelope, thus relying on these internal loads for a portion of the overall heating during heating months.
The building is also divided into four distinct vertical modules with fully-passively conditioned circulation spaces inserted between. This results in each apartment unit achieving a somewhat autonomous orientation whereas the north and south walls are thermally massive, yet allow in daylighting at a clerestory, while the east and west facades are completely glazed to maximize access to daylight and views. Shading at the west façade is optimized for solar orientation and access, and thus reflects natural light deep into the space, allows for passive solar gains in heating months, but prevents direct solar radiation during cooling months.
St. Louis lies within ASHRAE Zone 4 and is thus classified as a mixed-humid climate. In this region, cooling loads are much greater than heating loads, and humidity – without desiccants – makes incorporating passive cooling strategies difficult. Optimization for orientation, zoning, and fenestration help the building to achieve approximately forty percent of its heating requirements through passive solar and internal gains. In regularly occupied spaces, the acceptable humidity ratio was set at .012, (.04) above the comfort limit suggested by ASHRAE. The partitioning of programs and zones isolates and groups circulation and service space, allowing for non-regularly occupied spaces to rely upon passive ventilation completely for cooling as higher humidity levels are only a concern under longer durations of occupation.
Light and Air
The modulated plan affords each apartment access to natural daylight throughout the entirety of the unit. The commercial spaces at the first level feature a clerestory which provides the appropriate façade height for the desired daylight autonomy to be achieved. Each unit has 81% daylight autonomy. The modular plan also allows users large open views on both ends of the building, whereas 100% of the apartment units have views to the outdoors.
Due to a low wind velocity in cooling months, stack ventilation was employed to serve both the residential and commercial programs. This is facilitated by three light monitors enclosing circulation spaces. The glazed stacks protrude above the roof to serve as a thermal chimney, and maximize air buoyancy. Being as these neutral spaces are unconditioned, the ventilation mechanisms are automated. The openings within the building units are operated manually, but have the potential for automation as well. 100% of residential units, and 77% of commercial units are within 15 feet of an operable window.
Cross-ventilation is also incorporated in all units allowing air to pass uniformly through the entirety of the space.
A green roof is utilized as a means of collecting rainwater and reducing the heat island effect due to reduced hardscape on-site. Water collected at the green roof is stored at the garden level where it is used in drip irrigation to the adjacent community garden. Over 90% of the site is softscape – when including the green roof – and thus 100% of stormwater can be detained and treated on-site.
Greywater from showers, sinks, and other sources will be held on-site, treated, and recycled through these same systems. Solar hot water will be utilized to heat water for flow fixtures which will reduce electrical loads. Portions of detained water are utilized in a geothermal exchange that provides radiant conditioning to the building units, furthering passive building comfort, and reducing energy consumption.
Energy Flows and Energy Future
Geothermal heat exchange allows water to be circulated through a system of radiant chilled ceiling panels in the summer, and radiant floor heating in the winter. This system is approximately 20% more efficient than conventional forced air as losses are much lower, and thermal exchange is thermodynamically optimized (warm air rises from the floor, cool air falls from the ceiling).
Photovoltaics are applied at the roof and their angle is optimized for higher sun angles as cooling loads are much larger than heating, and thus at peak times, the building energy sources will be renewable. The panels can be rotated however, and will allow the building to take advantage of net metering at off-peak hours.
In addition to 7000 square feet of photovoltaics at the roof, 1000 square feet of glazed collectors provide solar hot water to building users. With all passive elements and renewable resources combined, the building only consumes 12.4 kBTUs/ft2 on average.
Materials and Construction
The primary structural system is cross-laminated timber (CLT). This is a material with a similar stiffness to concrete, yet is one-fifth the unit weight. It also has the potential to sequester up to one-half of its weight in carbon, leading to the potential of a carbon neutral structural system. Furthermore, it a pre-manufactured, pre-fabricated product allowing for greater control in the transfer of design to construction. This in-turn, somewhat de-industrializes the jobsite, thus decreasing the intensity of construction processes and their associated carbon emissions whilst minimizing the impact to the surrounding community and ecosystem. In this case, the CLT is left exposed at the interior thus eliminating the need for additional finishes and resulting in a simple, dematerialized aesthetic.
This design for assembly approach is advantageous from a life-cycle analysis perspective as it addresses not only the initial concerns related to embodied energy during construction, but also its potential to sequester carbon over its use, and its disassembly at the end of its life. The primary structural elements – and their associated connections – have been designed in such a way as to make their re-use compatible in other projects in the future. When quantifying these various considerations, the project achieves an overall carbon footprint near zero.
Long Life, Loose Fit
In visiting the site, we were astonished at the ability of the existing structures – which had been rehabilitated – to be reprogrammed for almost any use with very little retrofitting. Recognizing the existing scale, and the openness both in plan and in the street façade led us to develop a modulated design both in plan and elevation. This affords the building a certain fitness and flexibility. Scale, an openness to the public, and the importance of construction details dominated the development of this community for a century before certain broader demographic and more global forces led to its demise. Our project is a reinterpretation of this past as way of reinvigorating a latent vitality.
Collective Wisdom and Feedback Loops
For our team, a tension existed in the term sustainability. In one way, a sustainable building is one that acknowledges its context and adapts to the needs of its occupants. It is functional, and requires the occupants to commit to an interface with the architecture. It is a healthy, exciting, and invigorating place which is hospitable to a diverse array of people, uses, and programs.
Yet in another way, a sustainable building is one that is perfectly optimized in its resistance to environmental pressures. In this case, systems should be automated, and little user interaction can be allowed as it would disrupt a computationally derived efficiency seemingly acting in harmony with the inputs and parameters by which it was designed.
These competing definitions employ the classic poetic versus pragmatic debate, and it has been our goal to fully engage this project in that debate. This tension must be worked out in such a way that a building responds both to the needs of its users and the pressures of the environment, and we have learned that to do so, the processes of design must be thought through as thoroughly as the design itself.