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:

1. High heats of fusion, meaning they absorb or release a lot of energy before melting or solidifying; and
2. 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:

1. Leakage
2. Shape stabilized polymer/paraffin blends
3. 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?

Where do you see chemical engineers contributing to sustainable building design?