By Joshua Bowditch
Architecturally, the Lee County VA Healthcare Center (LCVAHC) in Cape Coral is an outstanding example of sustainability in southwest Florida. Sustainability can be defined as eco-friendly, efficient, and resourceful, and in regards to construction can be considered on the basis of building materials, specifically raw materials, supply chain, and characteristics of the end product. The basic components of building materials are geological resources which must be processed to some extent. The LCVAHC is clad with architectural precast panels by Stabil Concrete Products, and high-performance glass units by Viracon framed by curtain wall system by Kawneer. The south-facing front of the building features pilasters that angle outward as they rise to a large overhang, all of which provide an extent of sun-shading.
Architectural precast is distinguished by casting method and composition of the concrete. It is well-consolidated concrete with a low water/cement (w/c) ratio, instead of conventional self-consolidating concrete. These factors are made possible by casting the concrete at a controlled environment production facility. The distinctive aspect of precast concrete is impermeability, as it is impermeable to air infiltration and wind-driven rain1. During heavy rains, precast concrete may absorb some moisture at the surface, but the impermeability of precast concrete prevents moisture intrusion beyond a surficial extent, and it will dry out by evaporation1. The implications are controlling infiltration of moisture into the building envelope which is the goal in hot and humid climates, and resistance to weathering and efflorescence. Precast panels are unpainted and therefore are their inherent coloration. In this case the precast is integrally colored with iron oxide pigment to give a subtle earthtone coloration.
Architectural precast is a superior form of concrete because of its impermeability, thermal mass, and simplification of the exterior wall assembly. The use of architectural precast gives higher value and more sustainable utilization to the constituent materials than conventional types of concrete. These constituent materials are of significant economic interest and environmental concern in the state of Florida. Mining of suitable-quality limestone results in irreversible loss of natural habitats and detrimental impacts to environmentally sensitive surroundings2. Portland cement production is very energy-intensive and a major source of industrial emissions resulting from thermal decomposition of raw materials and combustion of fuels3.
The high-performance glass units are 1-5/16” nominal thickness, comprised of three plies of 1/4” glass; specifically, one ply of 1/4” Caribia glass with a VRE-59 coating at the inward surface, plus 1/2” airspace filled with argon gas, plus two plies of 1/4” clear glass with a laminate interlayer. Caribia glass is an aqua-green color that was produced by PPG Industries4. VRE-59 stands for Viracon Radiant low-E with nominal light transmittance of 59%5. The term “low-E” refers to reduced emissivity of heat from the glass surface. The low-E technology utilized by Viracon is magnetic sputtering vacuum deposition (“MSVD”)6, which applies metal atoms onto the glass to form a microscopically thin coating with spectrally selective, infrared reflecting properties. That is significant considering the solar spectrum is approximately 51% infrared, 47% visible light, and 2% ultraviolet light5. Visually, the VRE-59 contributes a crystal-like appearance7. Argon gas is invisible and nontoxic, having lower thermal conductivity than air8. It is used in combination with a low-e coating for optimal thermal performance8.
The curtain wall is Kawneer 1600 Wall System 1 IR (7-13/16” depth). This is an enhanced standard design with years of proven performance9. It features a thermal separator type thermal break made of EPDM which separates exterior metal components (pressure plate and snap-on cover) from load-bearing interior metal components10.
The pilasters and overhang are faced with Alucobond panels produced by 3A Composites, which are two sheets of 0.02” aluminum bonded to a thermoplastic core in between for a total nominal thickness of 0.157 inch11, 12. The panels are remarkably lightweight, reflective, and durable. The fluoropolymer finish provides an exceedingly high level of durability. The panels use 70% less aluminum than conventional 1/8” aluminum plate, thereby having the advantages of aluminum but in significantly lower quantity. This is significant considering virgin aluminum is especially energy-intensive to produce13, but aluminum can be considered highly sustainable when used sparingly.
Aesthetically pleasing as the LCVAHC may be, these aspects described would be generally unknown. It is publications like this one that can provide representation of these sustainability aspects through description and illustration. That would be the intent of “Architectural Stewardship”.
Acknowledgements
Special thanks to Jeff Rigot, Viracon Architectural Sales Representative, for specifics of the glass, Mary Aloisio, 3A Composites Sales Manager (AL, FL, GA, TN), for specifics of the Alucobond panels.
1Architectural Precast Concrete Manual, Third Edition. 2007. Precast/Prestressed Concrete Institute.
22009. Final Supplemental Environmental Impact Statement on Rock Mining in the Lake Belt Region of Miami-Dade County, Florida. U.S. Army Corps of Engineers (USACE).
3van Oss, H. G. 2015. Cement. Page 16.1-16.32. In: 2013 Minerals Yearbook. United States Geological Survey (USGS).
4Caribia® Spectrally Selective Tinted Glass by PPG. 2005. PPG Industries, Inc.
5Insulating Glass Specs & Tech. 2008. Viracon®.
6Architectural glass solutions from Viracon. 1997. Glass-Technology International (5): 308-314. Artech Publishing.
7September 14, 2016. Viracon’s New VRE-59 Coating Makes High-Profile Debut.
8Product Portfolio. 2018. Viracon®.
91600 Wall SystemTM1 / 1600 Wall SystemTM2 Curtain Wall: Imposing Statements – Used Together or Independently. 2007. Form Number 17-2220.B. Kawneer Company, Inc.
10Thermal Technology. Kawneer Company, Inc., 2020.
11Alucobond® Plus, Technical Data Sheet. 2020. 3A Composites USA Inc.
12Florida Product Approval #29842.1. 3A Composites USA Inc.
13Ehrlich, B. 2014. Cladding: More Than Just a Pretty Façade. Environmental Building News 23(9): 1-10.
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