Chemical Engineers Address Sustainable Building Materials
Since 2009, a handful of Environmental Division members have been
chairing a session on green building as part of the Division's
Sustainability Programming Area. The first year, the session featured
sustainable building materials, water conservation, and energy
efficiency. One of the session speakers included Myer Harrell, an architect from Seattle, Washington, and my co-chair in the local Seattle branch of the Cascadia Green Building Council.
Myer presented his work as part of the national award-winning team of
the 2008 Natural Talent Design Competition, sponsored by the US Green Building Council. His team's design, Eco-Lab,
is an innovative system that incorporates mixed-use building
applications, renewable energy generation and on-site water treatment.
Over the past few years, the chairs of the sustainable building
session have tried to cater to the interests and experiences of chemical
engineers involved in furthering the progress of sustainability in the
built environment. Below, take a look at the brief descriptions of some
the presenters' papers of this year's "Sustainable Building Materials"
session. Once you're done reading, you can offer feedback in the
comments section on what types of topics in green or sustainable
building you'd like to see as part of Annual Meeting programming.
Eco-friendly flame retardant polymers
John Player with the U.S. Army Natick Soldier Research Development and Engineering Center
presented on "Eco-Friendly Flame Retardant Polymers." John explained
that a major problem encountered in military operations includes
improvised explosive devices (IED), which pose a large threat to war
fighters. Current flame retardant (FR) materials offer a high degree of
flame retardancy; however, these same materials pose significant
environmental risks through use of hazardous compounds, such as
halogenated polymers. John presented the Army's latest research in
developing a new class of cost-effective eco- and human-friendly FR
materials.
Environmentally friendly materials, according to John, should be
friendly along all points of the materials' life cycles, from production
to disposal. John's group has created novel polysiloxane copolymers
(PS) by incorporating additives (e.g. boron, organoclays, and
nano-fillers) through solvent-free synthesis. The PS-based FRs are
comparable in performance to Kevlar(R) and Nomex(R),
which John explained are of unknown toxicity, are highly insoluble to
coat, are formed through hazardous multi-step synthesis, and are
high-cost. John explained that the best performing materials include a
combination of organoclay fillers and boron. The expectation is that by
formulating an effective FR PS-based material, these same FRs can be
applied in the building industry, though the US Army is currently
prioritizing their use for soldiers in battle.
A second talk on flame-retardant polymers was given by Jeff Cernohous, CTO, Chairman and Founder of Interfacial Solutions,
a materials development and transfer organization located in River
Falls, Wisconsin. Interfacial Solutions has developed bio-based polymers
marketed under the deTerra(R) bio-based polymer tradename. Jeff
focused on the development of the construction industry's fire-rated
biobased polymer, deTerra PR146. He discussed similar flame-retardant
properties of the deTerra polymer; however, his talk also highlighted
the market demand for green products.
Interfacial Solutions' building clients seek the company's products,
such as the bio-based, flame retardant polymers, for such applications
as wall protection in hospitals seeking LEED certification. DeTerra is
even cited as a "green" alternative to polyvinyl chloride (PVC)-albeit
costly at about 50-70% more on a per pound basis for PVC. The health,
safety and environmental implications of PVC are linked to its useful
life's release of persistent toxins, additional chemical content and
disposal in the environment. The International Living Building
Institute's green rating system, the Living Building Challenge,
for instance, has included PVC on its "Red List" of materials that are
banned from use in construction of Living Buildings (the Red List also
includes asbestos, formaldehyde, lead and mercury). Google, for
instance, has "red listed" PVC from its newest buildings.
A
comparison of eco-friendly flame retardant polymers to commercially
available polymers shows the viability of green materials for building
applications.
Reducing energy consumption
Cory Jensen, an Environmental Division
member, presented on behalf of Phillip Saieg of the Alliance for
Sustainable Colorado, who could not attend. Cory summarized the
conversion of an entire city block into a sustainable environment,
servings as a test bed for new technologies. This block of buildings is
intended to reduce aggregate energy use by 50% and 75% by 2014 and 2016,
respectively, to help at least two historic buildings reach a net zero
energy profile. More information can be found at: www.livingcityblock.org.
Dr. Robert Peters,
Secretary of the Environmental Division and a professor at the
University of Alabama in Birmingham, shared results from a campus study
titled "Roofing Materials as Effective Means to Decrease Heat Loads on
Buildings." The study was initiated as a means to actively seek ways to
reduce energy costs on campus, primarily from the campus hospital. To
conduct this study, 15 "mini-roofs" were built to suit a variety of roof
types that allow a reduction of energy use inside the buildings: white
roofs - painted white and capable of reflecting heat, rather than
absorbing heat as black roofs do; and green roofs - vegetated and
capable of cooling buildings through evaporation and transpiration
(evapotranspiration) of plants. Each roof is equipped with a temperature
sensor that has provided data every ten minutes, every day for the past
three years (resulting in almost three million data points!).
Here's a summary of Dr. Peters' findings and short answers to the
question he posed: "What is the best type of roofing material for the
southeast US?"
- White roofs increase albedo
- but get dirty. Facilities staff seek semi-low maintenance building.
White roofs reach temperatures as high as 110? (in contrast to black
roof temperatures which can reach 200?!). Concrete pavers with epoxy
coating are one of better performers.
- Green roofs take advantage of evapotranspiration as heat/water pumps that move heat to air.
- In general, rainwater was shown to serve as an effective coolant.
Rapid cooling due to rain was a very effective temperature regulator.
Comparing the miscibility of paraffin
Fang Chen, a PhD candidate in the lab of Professor Mike Wolcott
from Washington State University's Civil and Environmental Engineering
Department, presented a paper on "Comparing the Miscibility of Paraffin
in Different Polyethylenes for Form-Stable Phase Change Materials."
Form-stable phase change materials (PCM) are utilized for thermal energy
storage. Their structure and properties are highly correlated to blend
miscibility, which can affect their efficiency on energy saving
applications. PCMs are characterized by:
- High heats of fusion, meaning they absorb or release a lot of energy before melting or solidifying; and
- Constant temperatures during phase change: a property that keeps object at a uniform temperature despite external conditions.
Phase change materials are useful as green building blocks.
As a result of these properties, Fang described a study performed on
paraffin, a PCM. Paraffin was an appropriate choice for the study
regarding building materials because in building applications, a primary
objective is to keep the building at a constant temperature using
cost-effective means.
A problem of using PCM as an insulator, however, is that while
melting, the material will liquefy. As such, Fang investigated the
following problems:
- Leakage
- Shape stabilized polymer/paraffin blends
- Miscibility
The miscibility evaluation of paraffin in three types of
polyethylene as form-stable PCM was carried out by differential scanning
calorimetry and atomic force microscopy. An 18-carbon long paraffin
chain was compounded with HDPE, LDPE and LLDPE separately by employing a
parallel co-rotating twin screw extruder. Partial miscibility of
paraffin in polyethylenes was established. Miscibilities of paraffin in
polyethylenes were compared, based on degree of existence of the
intermediate phase, crystallization temperature shifting, equilibrium
melting point depressions and changes on crystallinity. Fang's
conclusion was that paraffin has a miscibility with the polyethylene
identified in this study in the ascending order of
HDPE<LDPE<LLDPE.
Green masonry materials
Finally, Dr. Tom Marrero of the University of Missouri offered a
helpful literature review of green building materials research from
masonry-based building materials (such as brick or concrete) to
polymer-based building materials. Dr. Marrero discussed the usefulness
of composites in green building materials. Composites describe two
materials that, when combined, are made stronger than individual
materials. Composite reinforcement is achieved by the addition of even
more materials, such as glass, carbon/graphite, or nano-materials. One
advantage of composites, furthermore, is their resistance to corrosion.
For example, fiber-reinforced polymer (FRP) materials can provide more
durable performance compared to steel (susceptible to corrosion) in
concrete structures.
Major issues Dr. Marrero identified in the adaption of green building materials include:
- Costs
- Structural performance
- Durability
- The absence of building code to support their implementation
- Reduced investments in construction
Dr. Marrero's words of wisdom are that a possible increase in the
construction industry will occur when material choices become more
focused on reduced use of non-renewables and that he stressed the
importance of recycling materials for the production of new materials.
What types of sessions in green building design would help you on the
job? What would you like to know more about regarding green building?