White Paper Transmittal
Date: October 8, 2010
FROM (Construction Industry Institute Director):
Wayne Crew or CII Executive Committee
Construction Industry Institute (CII)
3925 West Braker Lane
Austin, Texas 78759-5316
Phone: (512) 232-3000
Fax: (512) 499-8101
E-Mail: wcrew@mail.utexas.edu
TO (Receiving Organization):
Research Committee, CII
CC (Breakthrough Strategy Committee Sponsor):
Dr. Carl Haas
White Paper ID
#124
White Paper Title
Impact of New Translucent and Transparent Materials
Essential Questions
New translucent and transparent materials are being used to create architecturally attractive and
functionally exposed structures. While these materials are introducing excellent new design
opportunities, related construction knowledge remains sparse. What is our level of knowledge on
their long-term performance and sustainability? Is it possible to have essential savings on
construction costs by using them?
Summary of Idea (1-2 paragraphs):
New translucent and transparent materials which made of polymers are being used more and
more in our industry to create architecturally aesthetic, functional and sustainable structures.
Polymers are relatively new as structural materials but they are already extensively used for
structural rehabilitation and for new construction such as pipelines and lightweight tension
structures. However, little research has been done on these material’s long-term structural
strength and durability. Polymers do not corrode as steel does, but they do deteriorate with time.
Furthermore, their failure is usually brittle and thus safety on the structures utilize polymers
depends on our understanding on how, and possibly when they fail.
Lightweight structures are known to be made out of textile membranes and foils. Textile
membranes’ applicability for construction comes from their strength and at the same time
temperature and corrosion resistance. They are mostly utilized as lightweight roof covers or
structural facades allowing designing a variety of aesthetic and practical structural forms.
Depending on the density of their weaving, textile membranes is more or less translucent but they
will never reach transparency. On the contrary, foils, in particular ETFE foils, satisfy this
requirement; their transparency can be compared with glass. They have been used as tension
cushions which are lightweight, transparent and flexible allowing creating novel architectural
spaces. ETFE can be a substitute for glass but due to lightweight and non-brittle behavior under
normal load conditions are much safer e.g. for seismic zones. As foils are much lighter than glass
they are much more cost efficient as they allow wider spans and lighter primary structures. The
freedom of forms without increasing the costs is also an advantage compared to glass. However,
ETFE cushions must be subjected to tension in order for the structure to be able to carry
transverse loads (only the inflated cushion has flexural strength). These stresses, combined with
environmental conditions and UV radiation, have a negative effect on the long-term strength of
these polymers.
There are many remaining gaps on our knowledge about how these materials behave in place and
how to handle them in the process of construction. For example, some remaining questions are:
1. What are the construction problems and risks for structures made from these materials?
2. What will be the long-term performance and sustainability of these structures?
3. Are there safety issues when constructing with these materials?
4. What are the building science impacts of these materials?
5. Would a better understanding of the materials behavior and structural analysis of these
types of materials reduce construction risk?
List of potential goals:
 Examine and report out on the impact of these materials on our industry
 Investigate other applications in construction where we can use these materials
 Build architecturally aesthetic, functional, sustainable and cost effective structures using
these materials
Request for:
Request for further review by the RC to include this topic in the research slate 2010.
Attachments:
The draft RFP discussed above and the white paper are attached.
Whi te Pa per # 1 2 4 ( Dr af t: O ct ob er 2 0 1 0 )
Author: Polak, M., Fish, J., and Haas, C.,
B r eakt h r o u gh St r at eg y C o mmit t ee
Impact of New Translucent and Transparent Materials
1. Need and Potential
In a rapidly increasing trend, new translucent and transparent materials are being used to create
architecturally attractive, sustainable and functionally exposed structures. Immense new design
opportunities are being introduced by these materials, however related construction knowledge remains
sparse.
2. Background
Areas of particular interest, include:
1. Structural glass,
2. Fluoroethylene ETFE foils, and
3. Woven textiles.
A description of ETFE, for example, from Wikipedia follows:
Ethylene tetrafluoroethylene, colloquially known by its abbreviation ETFE, is a fluorocarbonbased polymer (a fluoropolymer): a kind of plastic. It was designed to have high corrosion
resistance and strength over a wide temperature range. In addition it has a high melting
temperature compared to glass, ETFE film is 1% the weight, transmits more light and costs 24%
to 70% less to install. It's also resilient (able to bear 400 times its own weight, self-cleaning (due
to its nonstick surface) and recyclable. On the other hand it is prone to punctures by sharp edges,
therefore it is mostly used for roofs. In sheet form as commonly employed for architecture, it is
able to stretch to three times its length without loss of elasticity. Employing heat welding, tears
can be repaired with a patch or multiple sheets assembled into larger panels.
An example of its use is as pneumatic panels to cover the outside of the football stadium
Allianz Arena or the Beijing National Aquatics Centre (a.k.a. the Water Cube of the 2008
Olympics) - the world's largest structure made of ETFE film (laminate). The panels of the Eden
Project are also made of ETFE and the Tropical Islands have a 20,000 m² window made of this
translucent material. Commercially deployed brand names of ETFE include Tefzel by DuPont,
Fluon by Asahi Glass Company , Neoflon ETFE by Daikin,and Texlon by Vector Foiltec.
Fig. 1: Examples of ETFE-foil structures with air-inflated cushions:
Garden Eden, Cornwall, UK, 2001; Swimming Center, Beijing, China, 2008
3
Fig. 2: Movable ETFE- foil structure, open air theater, Duisburg, Germany, 2003
3. State of the art
Polymers are relatively new as structural materials but they are already extensively used for
structural rehabilitation and for new construction such as pipelines and lightweight tension structures.
Surprisingly little work has been done on the long-term structural strength and durability of these
materials, which is crucial for the safety and reliability of structures. Polymers do not corrode as steel
does, but they do deteriorate with time. Moreover, their failure is usually brittle and thus the safety of
structures that utilize polymers depends on our understanding on how, and possibly when, they fail.
Lightweight structures are known to be made out of textile membranes and foils. Textile
membrane structures are mostly done with coated fabric like (Poly-Vinyl-Chloride) PVC-coated
polyester, (Poly-Tetra-Fluor-Ethylen) PTFE-coated glass fiber or Silicone-coated glass fiber. The
weaving inside the materials carries the loads, like wind and snow, as well as the pretension forces. Their
applicability for construction comes from their strength and at the same time temperature and corrosion
resistance. Tensile fabrics are utilized as lightweight roof covers or structural façades allowing designing
a variety of interesting, aesthetically exciting and yet practical structural forms. Depending on the density
of the weaving, the textile membrane is more or less translucent but will never reach transparency.
Conversely, foils, in particular (Ethyl-Tetra-Fluor-Ethylen) ETFE foils, fulfill this requirement;
their transparency can be compared with glass. ETFE has been used as tension cushions which are
lightweight, transparent and flexible allowing creating novel architectural spaces. The cushions often the
most striking engineering structures due to their dynamically shaped three dimensional forms and
lightness. They can be a substitute for glass but due to lightweight and non-brittle behaviour under normal
load conditions are much safer e.g. for seismic zones. As foils are much lighter than glass they are much
more cost efficient as they allow wider spans and lighter primary structures. Compared to glass structures,
their appearance is much lighter and thus more sophisticated structures are possible: for example
overhead glass roofing is only possible with high safety standards, in contrast horizontal roofing with
foils is far more easily realized. The freedom of forms without increasing the costs is also an advantage
compared to glass. A normal ETFE structure costs about 50% of comparable glass structures, including
the saving costs for both the primary and secondary structural elements. However, ETFE cushions must
be subjected to tension in order for the structure to be able to carry transverse loads (only the inflated
cushion has flexural strength). These stresses, combined with environmental conditions and UV radiation,
have a negative effect on the long-term strength of these polymers.
ETFE has similar temperature features as Teflon. Initially, ETFE foils have been used for
greenhouses only, by simply clamping the material to a steel or aluminum frame. Today ETFE foils are
mainly used as air-inflated cushions with two or more layers of foil. The approximately size is 20 to 50
m² with a maximum span of 4 to 6 meters. At present, foils are manufactured in thicknesses of 10 µm to
4
300 µm with widths of approximately 2 meters. The ultimate tensile strength of ETFE foil is rather low
(400 N/ 5cm for a 200 µm foil). The tensile strength at 10% elongation is approximately half of the
maximum tensile strength. After 10% elongation (yield) the deformation becomes plastic and with
increasing deformations the strain hardening of the material is initiated. Hardening is the result of the
reorientation (due to stress) of the molecular chains. This stiffening process depends on the load rate and
the loading speed. The deformations reach easily 150 % strain and can rise up to more than 600 %,
depending on the loading speed.
4. Gaps
There are many remaining gaps in our knowledge about how these materials behave in place and
how to handle them in the process of construction. For example, some remaining technical and
construction related questions include:
6. What are the construction problems and risks for structures made from these materials?
7. What will be the long-term performance and sustainability of these structures?
8. Are there safety issues when constructing with these materials?
9. What are the building science impacts of these materials?
10. Would a better understanding of the materials behavior and structural analysis of these types of
materials reduce construction risk?
11. Can these materials be used to create weather protected domes to enable work in inclement
environments (Snow, Ice, Frozen ground, torrential rains, even possibly protection from hordes of
insects, etc.?
12. Could they be used to improve the temperature – level or freezing in Minnesota/Canada?
13. Would tinted versions work to provide a level of sun protection in harsh environments?
14. Can they be used as translucent sheeting between floor or pipe rack levels – lets in light, protects
from falling objects?
15. Can they be used as translucent bubbles as weather protection for Lunch areas, break areas, laydown yards, or warehouses, parking areas, gate entrances, etc.?
16. Would they work for containment over effluent ponds, clarifiers, etc. that can be used to capture
off gases/vapors and port them to safe place for mitigation?
4. Recommended Path Forward
A twelve month study to examine and report out on the impact of these materials on our industry
is recommended.
5. References
5