[ 4 ] A Building Like a Tree

Designers rarely now consult nature for aesthetic truths so much as they look to nature for functional ones.  Architects like Mitchell Joaquim invert the idea of the Primitive Hut, amplifying biophilic tendencies that transform the act of construction from “building” to “growing” and envisioning a hut that is not primitive at all but rather the result of technology in ecological balance (fig. 1).

fabtreehab31

In a less literal sense than Joaquim, architect William McDonough proposes designing “a building like a tree,” by mimicking processes like using sunlight to generate energy, and using natural technologies to sequester carbon, produce oxygen and clean septic waste.  Expanding on the idea of a building like a tree, McDonough envisions “cities like forests” that follow nature’s primary maximum that “waste equals food” as a strategy for societal carbon neutrality.1

Sustainable-Architecture-Design-Building

The Pearl River Tower, designed by Skidmore, Owings, and Merrill (SOM), and located in Guangzhou, China approaches the goal of a carbon-neutral building by outlining four broad tactics for achieving that goal that are all applicable at a larger urban scale; Reduction, Absorption, Reclamation, and Generation.  Their stated goal was to design “a structure that does not require an increase in the community’s need to produce energy.”2

1. Reduction:

The design of the Pearl River Tower utilizes triple glazed facades on the east and west and ventilated double wall facades with mechanized blinds on the north and south.  Additionally a chilled radiant ceiling system and low energy lighting system as well as a “dehumidification system which uses heat collected from the double wall facade as an energy source” among other strategies, serve to reduce the overall initial energy demand.

2. Absorption:

SOM defines absorption strategies as “those that take advantage of the natural and passive energy sources that pass around, over and under the building’s envelope.”3  These include a building integrated photovoltaic system, fixed external shades on the east and west facades, and controlled daylight harvesting.  The form of the tower accelerates wind, which is channeled through four vertical axis wind turbines placed within voids in the body of the building. This formal strategy of “holes” in the mass of the building allowed for a reduction in concrete and steel as the holes act as “pressure relief” valves for the building, reducing the overall wind loads.4

3. Reclamation:

The Tower incorporates energy reuse schemes i.e. using “waste as a resource” or “waste equalling food.”  “The basis of this collection of strategies is to harvest the energy already resident within the building. Once energy has been added to the building, it can be reused over and over again, Examples… include the use of re-circulated air for pre heat/cooling of outside fresh air.”5 

4. Generation:

The original design used 50 daisy-chained 65 KW micro turbines than run off of various gas fuel sources.  Had they been installed they would have been capable of generating more than 3 megawatts of power and the excess heat could have been reused within the building as well.  Because of bureaucratic and economic factors, the turbines were not installed.

The specifics of SOM’s strategies may seem redundant in places and somewhat arbitrary at times in regards to within each strategy the various tactics are situated.  However, this apparent murkiness belies the interdependent nature of the overall approach.  All of the Pearl River Tower’s implemented strategies combined equal 58% reduction of energy use compared to a conventional building.  It is a tremendous achievement and shouldn’t be minimized but it should also not be mistaken as “sustainable.”  If SOM had been able to install the micro-turbines, the Pearl River Tower would have produced more energy on-site than it consumed.  The turbines however, must run on kerosene, biogas, diesel, methane, propane or natural gas.  Except for biogas and potentially methane, each of those fuels comes with a significant carbon footprint, which leads to a more complicated picture of net-zero energy use or carbon neutrality.

Pearl River Tower Energy Strategies

References:

1 www.mcdonough.com/writings/buildings_like_trees.htm

2 Frechette, Roger E. and Russell Gilchrist. Towards Zero Energy. Dubai: SOM, 2008. 2

www.som.com/publication/towards-zero-energy

3 Towards Zero Energy. 6.

4 Towards Zero Energy. 10.

5 Towards Zero Energy. 7.

Photo Credit:

Fig. 1: Mitchell Jaoquim, Terreform Living House

http://inhabitat.com/index.php?s=terreform

Fig. 2: Rendering of Pearl River Tower, SOM

Fig. 3: Energy Reduction Strategies, SOM

www.som.com/publication/towards-zero-energy

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