Steel has been a popularly used structural building material since the early twentieth century.  Since then, it has changed the construction industry; bringing remarkable architectural designs to life.  For over one hundred years steel has provided many benefits to the design and construction industry.  One of the most important benefits to consider is its level of sustainability.  Since the early 1970’s, the North American steel industry has been investing a lot of money into becoming a more sustainable industry.  Half of the world’s steel is now produced in electric plants that generate zero CO2 emissions.  Steel is a highly recyclable material and is made of around 90% recycled content.  The material can also be recycled over and over again and has a reclaimed rate of 98% (AISC, 2010).  Steel is ideally used with many sustainable designs as it complies with specifications of efficient building envelopes.  In addition, steel produces minimal site wastes as it allows for precise on-site construction. 


However sustainable the material may be, there are still some deficiencies with on-site steel construction.  Two main aspects to consider are the length of time that it takes to complete the steel work on a site, and how many workers have to travel to that site every day.  On a daily basis, steel workers continue travelling long distances to and from construction sites.  On site welding is also necessary to meet structural specifications in the drawings.  While it is undeniable that steel is a sustainable material, the deficient aspects of steel are exposed when the on-site construction methods are assessed.


In order to use steel more sustainably, architects and engineers have looked to introduce steel to the prefabricated (prefab) building industry.  By doing so, it is possible to harness the benefits of both steel design and prefab construction, while the two cooperatively eliminate traditional inadequate aspects.  Conventional prefabricated construction is cost effective, especially residentially, saving up to 15% compared to onsite construction.  Most firms and companies that do prefab designs keep a working set of drawings of all their plans so the design process is very quick and done with limited liability since the design has been built before (Koones, 2010).  This is the main reason why the design costs are lower.  Prefab buildings cost less from a construction perspective because most of the labor is performed in a factory.  The workers only need to travel to and from a static job site, the factory, rather than temporary job sites that are very far away.  The dramatically decreased time of construction from start to finish is another important factor contributing to decreased construction costs and increased profit for developers.  Some prefabricated companies claim they can build a house in as little as five days (Blue Sky Homes, 2010).  While these designs have no basement and require little excavating, they are actually quite luxurious in terms of space and aesthetics. 

             
Revolutionary prefab designs that have been developed by engineers and architects utilize steel as a structural system.  Most steel prefab structural systems start with pre-cut, pre-drilled I-beams that can be rapidly bolted together onsite.   Engineers perform structural analysis on all designs of steel prefab to ensure quality and safety in design (EcoSteel, 2009).  The strength of the steel frame allows for longer spans; meaning larger, more spacious designs that traditional prefab material could not conveniently provide.  In this respect, steel is responsible for allowing a commercial sector for prefab designs, and residential homes up to 5,000 square feet (Kodiak, 2008).  The newest steel prefab designs choose to lift the structure on piloti, which in itself is not a new method.  Le Corbusier used this architectural technique in his prefab designs in the 1940’s.  Modern designs attain this using the I-beam columns that bolt directly to the floor beams.  In addition to inheriting steel’s durability and mold and mildew resistance, this design is sustainable because it allows for new construction without disturbing the environment with excavation.

Using a steel frame in prefab construction allows for a quick and easy installation just as traditional prefab does.  The installation process is even further enhanced because there is an abundance of contractors familiar with steel work.  Traditional prefabricated buildings use complex designs that often require special contractors to assemble which can be rare and expensive.  In steel prefab the extent of the construction complexity lies in the connections.  In order to ensure that the connections will not need welding on site, engineers have calculated bolt patterns that have been tested in the factory.  Some companies have even gone as far as patenting their techniques.  FCP Structures has patented their ConnectRite  technique that establishes a moment resisting, bi-directional frame using only bolts (ConnectRite, 2009).  This ensures that their product is reliable and can be assembled with ease onsite. 

With ease in assembly comes ease in disassembly as well.  This is a sustainable aspect to steel prefab for many reasons.  The lifecycle of a steel prefab home addresses the ‘cradle to cradle’ philosophy.  These buildings can be disassembled and recycled while leaving minimal impact on earth beneath it and recycled, or moved elsewhere and reassembled.  Also, additions and alterations to these buildings are made easy with the bolted steel frame. 



The role of steel is not limited to its structural components as prefabricated exterior wall and roof panels are being manufactured with steel.  The steel not only offers a higher strength to weight ratio, but also contributes to the durability of the walls and roof.  The concern for moisture in the walls is lessened as well as the need for harmful pest control because of the absence of wood based products that are common in traditional prefab buildings.  Three inch thick steel wall panels can achieve R-24 insulation and can easily be attached to steel framing as an energy efficient curtain wall system.  Also, R-32, 4-inch insulated steel panels can be used on the roof (EcoSteel, 2010).  Many other innovative components have been based on steel, and its capabilities.  Floor systems have also been pioneered using light gauge steel that is prefabricated into truss live beams that span long distances while creating eight to twelve inches of depth .  The beams are laterally braced by subflooring.  This essentially creates a panelized platform that can be attached to a steel column and girder foundation (Framecad, 2009).  The depth of the frame is filled with insulation for thermal and acoustic performance.


Historically, excellent prefab ideas have failed to catch on because of inefficient technology to conveniently reproduce housing projects.  Ironically, some of the same design techniques used 60 years ago are still relevant to the most popular prefabricated building trends today.  However, today we have taken the ideas of these prefabricated panel systems and produced energy efficient panelized walls that hang on a structurally sound steel frame.  These innovative steel prefabricated buildings seem promising as they have proven to be versatile, durable and can be quickly built anywhere.  In the near future steel prefab will be used for hurricane relief and to develop high capacity sustainable communities.  Overall, steel plays a large role in the advancement of the prefab building industry, and introduces many new qualities to prefab designs that will increase the popularity of this construction method.




 

Sources

"AISC: Designing for Sustainability." American Institute of Steel Construction. AISC, 2010. Web. 27 Apr. 2010.

"Blue Sky Homes Building System." Blue Sky Homes. Web. 23 Apr. 2010. <http://www.blueskyhomesllc.com/content.html?page=2>.

"ConnectRite." FCP Structures. Web. 25 Apr. 2010. <http://www.fcpmezzanine.com/connectrite>.

"EcoSteel: System Overview." EcoSteel Building Systems. Web. 25 Apr. 2010. <http://www.ecosteel.com/solutions.php>.

"Framecad Floor Systems." Steel Frame Design. FRAMECAD, Web. 28 Apr. 2010. <http://framecad.com/products/building-systems/floor-systems>.

Koones, Sheri. "Prefabulous + Sustainable." EcoSteel Building Systems. CBS Money Watch, 30 Mar. 2010. Web. 25 Apr. 2010. <http://moneywatch.bnet.com/saving-money/blog/home-equity/prefabuloussustainable-why-prefab-green-homes-are-the-future-of-home-building-in-the-us/1822/>.