DESIGN

SITE-HARVESTED AND WASTE MATERIALS: “BUILDING GREEN” COTTAGE

There is a movement in the US to rekindle traditional building systems. The concept is that these approaches are less environmentally destructive while creating comfortable, efficient, beautiful spaces. To the extent which this is true, the success of indigenous building systems lies in the fact  that they were developed in a specific cultural and climatic context. For example, in hot arid climates with diurnal temperature swings above and below desired interior temperatures, thick earthen walls can act as a form of dynamic insulation to create very comfortable spaces. However, transplant this same system to a wet, cold climate and you essentially have a car without an engine as the passive mechanism which drives the building system isn’t present. The question is can we access the considerable archive of building knowledge represented by indigenous systems and apply them to our contemporary context? This project was conceived to answer that question by applying site-made, local, and recycled materials and passive systems appropriately based on building science principles to create a tiny, flexible, efficient, and beautiful fully functional living space. Different building methods were compared based on performance in relation to a specific microclimate. For example, earthen materials (cob and clay-slip straw) were used on the south face of the building to take advantage of thermal mass to collect solar heat in the winter while straw bales where used on the north face because of their high thermal resistance. The project was conceived as a teaching tool and was designed and built to be documented as a book.

MASS-PRODUCED HYGROSCOPIC ENVELOPES: THE NAUHAUS

Traditional systems are great, but, let’s face it, times have changed. Our buildings have a more complex job these days as they are asked to provide a very stable interior comfort zone complete with running water and wireless internet. Also, mass production has lowered costs. If you don’t believe me go out and price a thatched roof compared to a high quality standing seam metal roof. And when it comes to financial and environmental impact, the materials themselves are only a small part of the story. It’s the operation of the building (heating, cooling, and plug loads) that is responsible for most of the resources a building uses through its life. Still, we don’t want to throw the baby out with the bathwater. Can we maintain the core wisdom of indigenous systems, which in my estimation is low-embodied energy materials and passive design tailored to microclimates, while tapping the benefits of mass-production and advanced building science? The Nauhaus Project was conceived as an attempt to do just that. The project was designed to the Passivhaus standard, probably the most rigorous building energy standard in the world which requires very careful design of an airtight thermal-bridge free envelope that allows a lower impact mechanical system and provides superior indoor environmental quality. The wall system, however, was intended to emulate many traditional systems in that it utilized mass in a hygroscopic assembly. The material chosen, Hemcrete, was made from a waste material (shiv) but engineered, packaged, and sold as a mass-produced product allowing for quality control and accurate cost estimation. Site-made materials were used when they fit the performance goals. Interior floors and mass walls are compressed earth block made on site and the interior is plastered with a variety of earthen plasters. Many innovative systems were incorporated combining simple passive technologies with high performance mechanicals. The design minimized interior square footage with extensive use of outdoor rooms creating an incredibly comfortable living space that can be heated by the body heat of ten people on the coldest day of the winter in fairly cold climate (Asheville, NC). If you want to know more, here’s an entire website on the project.

Nauhaus Animation
Why Nauhaus?

FIXING CONCRETE:  URBAN EDEN PROJECT

Over the past 10 years as climate change has continued to rear its progressively uglier head, my focus has turned more toward its mitigation as a design challenge. In terms of the built environment, concrete is center stage. On the one hand, it is responsible for a huge percentage of our collective carbon footprint, on the other it has great potential to save energy as part of an intelligently conceived building envelope. Concrete is, after all, a traditional material with thousands of years of history. It is hygroscopic and massive like the lion’s share of the systems I had been studying for years. While I was a graduate student at UNC Charlotte, we designed and built a project that I consider a step in the direction of “fixing concrete”. We applied research being done on campus to use a new kind of concrete, geopolymer cement concrete, that represented a massive reduction in carbon footprint in a high performance envelope of our own design. The project was UNCC’s entry in the 2013 Solar Decathlon which required it be a small, completely solar-powered house. We conceived it as an urban infill project for Charlotte and wanted to create a building that claimed its own private outdoors. We did this by essentially combining indoor and outdoor rooms into a single living environment. To read my more extensive architectural description, go here.

UrbanEden promo video
UrbanEden context interviews

FIXING CONCRETE: THE “PASSICHANICAL” WALL SYSTEM

Passive first, then active. That’s my design philosophy. Passive design requires an understanding of the science of how specific climatic variables interact with building materials and assemblies. In buildings, passive happens in the zone of the envelope and so I’ve come to see envelope design as paramount. Recently, I’ve been working with Thomas Gentry and Brett Tempest to develop a high performance wall system that blurs the line between building envelope and mechanical system. I’m calling it “passichanical” somewhat tongue and cheek, but maybe that will stick. Here’s a brief slighty technical synopsis of the design:

Building envelopes save energy by reducing the work required by mechanical systems to maintain interior comfort. They can accomplish this in at least three basic ways: 1) resisting the flow of heat with insulation; 2) storing heat with mass; and 3) regulating solar heat inputs to maximize or minimize gains through glazing and shading strategies. The current state of the art in the US focuses primarily on #1 for residential construction and on #3 for commercial construction, therefore considerably reducing the potential efficiency of standard building envelopes. When mass is incorporated in envelopes it is usually not configured to take advantage of thermal characteristics. In addition, as we’ve said, the ubiquitous mass material in use, portland cement concrete, requires huge primary energy usage to produce and consequently is responsible for approximately 7% of worldwide carbon emissions.

To address these deficiencies in current building envelope design, a wall system has been developed and is currently being studied at UNC Charlotte that consists of an optimized, engineered combination of innovative technologies creating a dynamic building envelope : 1) a geopolymer cement concrete (GCC) that drastically reduces the primary energy required to produce concrete; 2) a thermo-active building system (TABS) that utilizes hydronics, increased mass surface area, and roof mounted heat exchangers to deliver low-energy heat transfer in and out of the wall; 3) a carbon fiber epoxy composite that creates a structural connection between interior and exterior concrete wythes without thermal bridging or compromising hydronic thermal exchange; 4) an approach to macro-encapsulated phase change material (PCM) application that eliminates the partial phase change phenomenon common with PCMs; and 5) a unique approach to concrete mix design that optimizes for thermal performance through calculated attenuation of paste to aggregate ratios based on desired thermal response . These innovations in combination with existing continuously insulated, thermal bridge free precast concrete technology produce a revolutionary wall system that maximizes performance in all three categories for envelope energy savings: 1) insulation levels are not limited by cavity depths as in framed construction; 2) mass is configured inside insulation to take full advantage of thermal storage with volume and mix design easily adjustable to meet climate and site specific high performance requirements; and 3) the interior concrete wythe becomes a multi-layer passively augmented component of the mechanical system allowing for nuanced control (input or removal based on season) of solar and other heat sources.

TOOLS: DRAWING, MODELING, GRAPHICS

My main design tool is Revit because I really like the ever expanding list of performance modeling features. As we generate results in the lab for the thermal characteristics of a material or assembly, for example, I can apply that data to materials and assemblies in Revit. On the modeling side, in addition to Ecotect and Vasari, I also have used BeOpt, Therm, Radiance, and Green Building Studio. I like to use Rhino and Grasshopper for basic iterative modelling and can get around the full Adobe Creative Suite. I built this site using WordPress.

WHY?
I grew up in the intense heat of Central Texas where everything living is in a constant search for shade. Whether a cow under a tree or a dog under a porch, the rationale was consistent and obvious. This logic was carried through by us humans in the older neighborhoods where houses with large front and screened back sleeping porches were nestled under the spreading canopies of oak trees clearly older than the houses themselves. This changed. Maybe it was the arrival of air conditioning and the money to be made by replacing trees with more houses. Whatever the reason, newer neighborhoods were treeless and porchless and HOT. The contrast was stark and unequivocal. The newer neighborhoods (tellingly relabeled “developments”) locked in a dependence on fuel driven, breakable mechanical systems and set a hefty baseline energy usage. They also defined two completely distinct environments, with the inside becoming a sort of prison of comfort discouraging inhabitants from venturing outside as part of their daily home life.  The older neighborhoods, on the other hand, used passive strategies (trees, overhangs) to adjust the microclimate around the buildings toward the human comfort zone, lowering cooling loads and therefore baseline energy demand while creating a “third environment” around the house that encouraged a lifestyle that included being outside.. I didn’t realize it then, but this was my first lesson in passive design and it set the tone for my future work in sustainable design. Though I see mitigating climate change as a central macro-rationale for my work, I believe that the sensible path to efficiency leads to a better, healthier lifestyle. Over the years I’ve gotten deeper into science of building envelopes and increased the scale and scope of the projects and materials that interest me, however the throughline in my research has remained constant and can be described by the motto: passive first, then active.
WHAT?
I conduct research into materials, assemblies, and systems in the context of building envelopes. I am particularly interested in high performance assemblies and how to configure them so that they interact with site conditions to minimize heating and cooling loading while maximizing durability. My associated research life has comprised essentially three phases: (1) site harvested and waste materials modeled on traditional hygroscopic systems; (2) mass produced materials and assemblies that increase functionality within the existing construction industry while maintaining certain benefits of traditional systems; and (3) concrete technologies, specifically with the goal of improving concrete’s carbon footprint and maximizing its thermal performance potential in building envelopes.
HOW?
I generally try to connect all research I do to a design project and connected publication. Sometimes this cycle has been very personal. For example when I lived in a two room mountain log cabin for three years and took a self-directed course in homesteading. Most often it has been tied to residential design and publication projects. As my interests have moved toward the larger scale and industrial, I have moved into a traditional academic lab research and journal/conference publication paradigm.