Tag Archives: net zero energy

Shipping Container Architecture: Advantages and Challenges


Cité A Docks Student Housing project located in Le Havre, France. A four-story building that houses 100 apartments made of old shipping containers.

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Conceptual rendering, BOOM Single-Family Residential and Community Center, Palm Spring, CA

Shipping container architecture is a construction type which uses steel intermodal containers (shipping containers) as the building’s primary structure. Given that there has been a sustained interest in the type, particularly in green building design circles, an objective appraisal seems appropriate. Fundamental considerations include aesthetics, the advantages of this construction type, and the challenges to be overcome if the form is to be viable as an alternative to conventional construction.


In order for shipping container architecture to be a viable alternative in any given application the first consideration is aesthetics since, obviously, the rough and tumble outward appearance of the building type is not for everyone. That said, given that the type is identified with – and even emblematic of – sustainability as a system of values, the shipping container aesthetic can be seen from that perspective as a strongly positive attribute.


Assembly diagram of Container City, a realized project in the Trinity Buoy Wharf area of London, showing how the unit shipping containers (each nominally 40’x8’x8′) are stacked.

More importantly, as the building type becomes more mainstream, the general public’s reception towards the aesthetic can only be destined towards the positive. By way of example, strawbale construction, which only fifteen years ago was widely regarded as the lunatic fringe, is soon to be incorporated into the building codes and has come to be regarded as representing a certain environmentally refined sensibility. Similarly solar panels, decried as unsightly by most city beautiful advocates only ten years ago, have emerged as the default symbols of the eco-chic.

This shift towards public appreciation of the aesthetic seems to me just as inevitable, and for exactly the same reasons.


A realized single-family residence in Savannah, GA built by Price Street Projects


If in fact aesthetic content is seen as an upside bonus to this construction type, other positive considerations follow. These include:


The Southwest Texas Alternative Energy and Sustainable Living Field Laboratory under construction in Alpine, Texas.

Adaptive re-use: re-purposing the containers as raw material for construction makes sense from a sustainability perspective inasmuch as these are surplus materials of the shipping industry which would otherwise be melted down for their steel content. A container has 8,000 lb (3,629 kg) of steel which takes 8,000 kWh (28,800 MJ) of energy to melt down, making re-purposing a to-be-desired outcome from both economic and environmental vantage points.

Prefabricated: the containers themselves as a building element represent a prefabricated, weathertight, structural shell offering the promise of economical assembly and realization.

Strength and durability: Given that they are designed to withstand significant, repetitive dynamic loading, the units are rigid, durable, and structurally robust.

Modularized: the inherent modular nature of the units lends itself to an economy of means, both in configurations placed alongside one another horizontally as well as those stacked vertically. It is reported that a stacked configuration can be as many as twelve container units in height.

Transportable: as a raw material, given their nature as containers, they are readily transported to all but the least accessible construction sites.

Availability: More than 21,000 shipping containers arrive in the United States on a daily basis. Most originate overseas, where it is cheaper to build new containers than to ship them back after their maiden voyages. Reportedly at any given time there are upwards of 700,000 containers are stockpiled on prime waterfronts throughout the U.S. This plentiful supply combined with relatively low demand means that they are prospectively an economical commodity, reportedly costing as little as $900 per container unit.


Public low-cost housing project at waterfront location in South Africa.

Constructability Challenges

Although there are both intrinsic and tangible upside benefits, the downside constructability challenges bear careful consideration. These include structural integration, introduction of openings, systems integration, waterproofing, and passive solar design challenges.


Puma City, an 11,000 square foot transportable retail and event center. The building has been assembled and disassembled a number of times at several different international ports.

Although the containers themselves are strong, their interface with the ground should not be overlooked. It’s not a matter of simply locating them in position, leveling them on the raw ground, and calling it “done”. To carry gravity loads sufficient to resist subsidence as well as carry lateral (wind and earthquake) loads requires a code-conforming foundation system. Construction of same, together with a method of attachment to the container which does not comprise weather-tightness, is the first of many factors having the potential to erode their ultra-low cost effectiveness.

Introducing door, window, and skylight openings must also be attended to carefully, both in the design and during construction if the final result is not to leak. The addition of these elements, especially combined with the meticulous level of workmanship necessary, can be expected to be amongst the more significant costs in the final budget work-up.

Interior of PUMA CITY

Interior of Puma City.

Systems integration, the introduction of provisions for plumbing, mechanical heating and/or cooling, and electrical necessities such as power and lighting, is an essential consideration if for no other reason than that every penetration though the compartment shell will need to be carefully attended to for purposes of waterproofing. Although taller containers have an interior height of 9’-6”, standard containers are slightly less than eight (8) feet high, meaning that with forced air systems soffits for ductwork have the potential to become an oppressive feature. Raised floor radiant heating, again because it infringes on floor-to-ceiling height, suffers similar drawbacks.

Lafayette Tower, a high-rise live-work tower composed of shipping container housing units with a structural concrete and glass matrix.

Lafayette Tower, a high-rise live-work tower composed of shipping container housing units within a structural concrete and glass matrix.

In terms of waterproofing, although the containers themselves are weathertight, they need to be augmented with a sloped roof assembly in order remain so over the long term. This is because the containers, being meant for stacking, are not designed with upper surfaces sloped to shed water. In the lifetime of the building, unless protected with an exterior roofing element, the upper surface of the metal shell will eventually fail.

For further reading: A candid, realistic listing of some costs/ benefits of shipping container architecture together with some experience-based, practical advice can be found at: http://www.jetsongreen.com/2010/02/ten-things-consider-shipping-container-projects.html



Net-Zero Buildings


One NZE building: the Research Support Facility in Golden CO, approximately 50% more efficient than it’s conventional counterparts.

The noted American green building architect William McDonough is famously quoted as once saying that buildings should, among other qualities, “live off current solar income”. What was merely a hypothetic concept in the early 1990’s has since firmly taken root: Net zero energy (NZE) has taken on significant momentum as one of the factors shaping the sustainable construction movement.

With the U.S. Department of Energy’s 2009 mandate that all new federal buildings will be NZE by 2030, deployment of NZE is now national policy. Beginning with the city of Austin, TX in 2009, local jurisdictions have since followed suit. Here in California, the next iteration of the Title-24 Energy Code (scheduled for July 1st) will require all new residential buildings to be NZE by 2020 and new commercial buildings to conform by 2030. As a relatively new concept in the construction industry, much ambiguity still exists as to terminology, definitions, and usage of the term Net Zero Energy.

A useful description can be found in “Sustainable Construction: Green Building Design and Delivery” which offers, “In general, these are grid-connected buildings that export excess energy produced during the day and import energy in the evenings, such that there is an energy balance over the course of the year. As a result, NZE buildings have a zero annual energy bill with the added bonus that they are considered to be carbon neutral with respect to their operational energy.”

In her popular and highly influential book Energy Free: “Homes for a Small Planet” (Green Building Press, San Rafael, CA), Ann Edminster offers four (4) definitions, each taken from a different perspective e.g. energy usage at the project site, usage at the energy source, cost of the energy used, and by emissions associated with the energy usage. Of these, the most useful are the first and the last.

The first of these, again taken from the perspective of the building, reads: “Net-zero site energy (Definition 1). A site zero energy building produces at least as much energy as it uses in a year when accounted for at the site”.

The fourth definition reads, “Net-zero energy emissions (Definition 4). A net-zero emissions building produces at least as much emissions-free renewable energy as it uses from emissions-producing energy sources.”

In Europe, the most influential leadership towards NZE seems to be that of the International Energy Agency (IEA), an NGO based in France. Working within the framework of IEA’s “Solar Heating and Cooling Program Task 40: Energy in Buildings and Communities” initiative, researchers in 14 European countries plus the U.S., Canada, Singapore, Korea, Japan, Australia, and New Zealand are working to bring NZE into international market viability.


Rendering of NREL’s Research Supporting Facility depicting just a few of its “green” features.

A good exemplar of an NZE building in this county is the National Renewable Energy Laboratory’s Research Support Facility (RSF), located in Golden, Colorado. This 360,000-square-foot, four-story office building’s energy use goal is estimated at 34.4 kBTU/ft2/yr. According to U.S. EPA’s Energy Star, the national median site EUI for office buildings is 67.3 kBTU/ft2/yr, making the RSF approximately 50% more efficient than it’s conventional counterparts.

To learn more about NZE, some helpful resources include the U.S. Department of Energy Building America website, that of the Solar Heating and Cooling Programme, and Zero Energy Buildings: A Critical Look at the Definition.

Your Ecological Footprint

Recycle BuildingEcological footprint is a term commonly used in sustainable building practice as a measure of our demand on earth’s resources. More specifically, it represents the amount of biologically productive land and sea area necessary to supply the resources necessary to a given population. Since resource utilization is dependent on personal lifestyle, the ecological footprint can be considered to be a quantification of the demand for natural capital needed to support a given lifestyle.

This unit of measure was first conceptualized in the PhD dissertation of Mathis Wackernagel under the supervision of William Rees at the University of British Columbia in Vancouver in 1988. Originally the two men called their concept “appropriated carrying capacity”. The revised term, “ecological footprint”, was coined in their book, “Our Ecological Footprint: Reducing Human Impact on the Earth” in 1996.

When calculated at the level of cities and countries, the measure provides a useful indicator of the relative demand on resources for any given population base. An ecological footprint calculation indicates that, for example the Dutch need a land are 15 times the physical footprint of the Netherlands to support their population. The population of London requires a land area 125 times greater than its physical footprint. William Rees’ ecological footprint analysis of his home city of Vancouver, Canada indicates that Vancouver appropriates the productive output of a land area nearly 174 times larger than the city’s physical area to support its lifestyle.

When considering the ecological footprint on the individual level, given Earth’s 8.9 billion hectares of productive land and its 6 billion human inhabitants, the average ecological footprint comes to roughly 1.5 hectares per person.  This per-capita footprint provides a benchmark from which to assess the long-term sustainability of material consumption.  Accordingly, individual footprints below 1.5 hectares are sustainable and footprints above 1.5 hectares are not. Wackernagel and Rees’ original calculations indicate that inhabitants of industrialized countries often have footprints as large as four (4) to ten (10) hectares, i.e. up to six times the carrying capacity of the planet.

What is your personal ecological footprint? A number of non-governmental agencies (NGOs) offer online ecological footprint calculators. One of them is at Footprint Calculator.

Some resources available for further reading include Wackernagel’s original thesis “Ecological Footprint and Appropriated Carrying Capacity: A Tool for Planning Toward Sustainability” and William Rees’ 1992 paper, “Ecological Footprints And Appropriated Carrying Capacity: What Urban Economics Leaves Out“.

The San Francisco Federal Building

San Francisco Federal Building

San Francisco Federal Building

Most of us have noticed the new Federal Building complex in South of Market – it’s readily apparent and distinctive from both the route 101- and 80- freeways. Fewer are aware that the building is widely regarded as a cutting-edge example in the art of high-performance green building.

Owned by the Government Services Administration (GSA), the facility serves the Social Security Administration, Department of Labor, Department of Health & Human Services, and the Department of Agriculture. The design team was led by Morphosis Architects of Los Angeles and included the LA office of Ove Arup for the integrated structural and mechanical design.

The complex consists of several components including a four-story structure housing the SSA, an undulating form at plaza level accommodating a day-care center and cafeteria, and the dominant, 18-story tower.


The perforated skin of the Federal Building controls light and airflow through the building

The folded, perforated metal skin covering much of the southeast face of the tower assists in the flow of air throughout the structure – this façade is also covered with perforated panels that rotate to control daylighting as well as provide unobstructed views across the city. The thin-section organization of the tower facilitates passive cooling and ventilation throughout the structure, taking advantage of ambient air temperatures and air currents around the building and directing them via building elements, including the perforated skin, that direct the deep penetration and circulation of outside air.

Altogether, the net result of these strategies is to realize a 26% reduction in lighting energy and a 39% reduction in mechanical systems energy compared to average GSA building usage.

Design for Sustainability


In an age of prefab homes, remodels and additions, the built environment is constantly changing. Rarely does a building’s original structure endure these changes, resulting in waste and consumption of materials and energy. The few structures that do withstand demolition, however, tend to be historically and culturally significant. In being so, a building’s capacity to sustain these stressors is reflective of valuable design.

The “one size fits all” design aesthetic that emerged in the global age “tend(s) to overwhelm (and ignore) natural and cultural diversity, resulting in less variety” and a loss in cultural significance (McDonough 2002: 33). Thoughtless design perpetuates sprawl, uniformity and meaningless development. Without authenticity, or an intention for cultural development, the built environment looses its importance in the community.

With the environmental context, the materials used, renewable energy sourced and level of LEED certification obtained traditionally measure a building’s sustainability.  Although there is great importance in these aspects of green building, the element of design is considerably overlooked.  Beyond aesthetics, design is seldom considered a factor of sustainability. Original design, reflective of the community it was built for, establishes an intergenerational significance. Culturally significant buildings that are representative of the community, inevitably survive longer by being restored and reused. In contrast, insignificant design perpetuates uniformity and eventual demolition- enabling the cycle of waste and consumption. Authenticity is essential in determining a building’s value, duration of occupancy, lifespan and sustainability.

This longevity aids in the creation of culture, and lasts across generations. Failure to construct a building that is representative of its culture, will impact its ability to survive, resulting in demolition, abandonment, and reconstruction. Thus, thoughtful, original design is the ultimate factor in determining a building’s sustainability- its capacity for durability and reuse.

Photovoltaic Assessment with Consumers in Mind

Dear Reader,

This is the first in the series of contributions to our blog by Anna Medina, Daniel Silvernail Architect- UCSC Green Building Intern. We welcome Anna to our team!

PhotovoltaicsWhen considering going solar, it is important to understand the financial costs and varying scales of environmental benefits associated with different systems. Navigating through the myriad of options for solar panel types, sizes and installers, it is difficult to assess the degree to which you are making an environmental difference for the finances you are supplying. Finding a system that is right for you is influenced by several factors such as scale, efficiency, life span and the installation company you choose to use. These decisions most directly affect the cost of your solar system, however, the purpose of this article is to better inform your decision in which panel technology you invest in, and to reassure your transition to solar power.

The difference in photovoltaic cells is characterized by the elements they use. The two most prominent materials used in photovoltaic’s are silicon and cadmium telluride (CdTe). Silicon is the second most abundant element in the world, after oxygen, which eliminates issues of resource scarcity and the extensive mining patterns associated to retrieving rare earth minerals. The consequences of silicon mining are minimal in comparison to coal and petroleum, since there are zero carbon emissions and it is not an environmentally hazardous substance. On the other hand, CdTe is known to be ecologically toxic, but is most commonly acquired as a byproduct of zinc winning. Thus, employing CdTe in solar panel production is an effective way in diverting toxic waste from landfills. CdTe remains in the solar market behind silicon panels because it tends to be more cost effective, although less energy efficient. Overall, both silicon and CdTe models are sustainably comparable, however, the production and manufacturing of silicon panels poses less risks because it is a non-toxic substance.

The environmental analysis of solar energy extraction, production and waste disposal operations make evident the significant environmental advantages over traditional coal and petroleum. While there is no perfect solution to meeting our energy demands with zero environmental impact, solar energy is the best option available. Operations with preferable extractive techniques and relying on abundant materials, solar energy is the most viable alternative to coal and petroleum. Going solar ensures the availability of energy with minimal impact on the environment while also alleviating energy dependence on fossil fuels.

The Modern Strawbale House: Machine for Sustainability

In January 2004 we were invited by Depth Magazine to contribute an article about sustainable architecture. I decided to write an educational piece about strawbuilding, a portion of which we reproduce. Enjoy!

The Modern Strawbale House

The goal of the modern strawbale house is conservation of earth’s resources. To this end such a house is an assembly of concrete, timber posts, metal bracing, prefabricated trusses, and bales of straw – materials and systems selected to reduce reliance upon wood as a building material.

black background copyPosts are the skeleton of such a house, and bales are its skin, or “infill”, on three of its sides. The fourth, facing south, is conventionally framed, making the house a hybrid structure, admitting of larger expanses of south-facing glass and the solar benefits which accrue to this strategy. Passive solar design is an essential component of the modern strawbale house.

Straw – ubiquitous waste product otherwise sent into the atmosphere as greenhouse gas – bound as bales, stacked like bricks, gives thickness and heft to its walls, lending them comforting reassurance and sculptural majesty. Insulation is the natural gift of straw used this way, retaining the heat passively gained in winter, fending off unwanted heat in summer.

Anatomy of the Hybrid Strawbale House

Anatomy of the Hybrid Strawbale House

The ridge of such a house is oriented east-west, exposing its long, south flank to the sun. Set at right angles to its rays, the roof is a plane designed to support an array of photovoltaic cells, capturing the sun’s rays as electricity, diminishing reliance on hydrocarbons as an energy source.

With appropriate modifications, such a house can be suitable in nearly any climate, within nearly any budget. The modern strawbale house is a machine for sustainability.

Daniel Matthew Silvernail Architect is a professional practice in Santa Cruz California. An ecologist by training who migrated quite naturally into the profession of architecture, and then (somewhat more serendipitously) into straw building, Daniel can be contacted at (831) 462-9138 or via Email at info@silvernailarch.com. The website is http://www.silvernailarch.com.