Posts Tagged ‘Glass Fiber Reinforced Concrete’

Shepard Hall: Buildings = Energy Exhibition at The Center for Architecture, New York City

Tuesday, October 4th, 2011

Elemental is proud to announce that it’s award-winning historic reconstruction of Shepard Hall at The City College of New York is included in the current exhibition on view at the Center for Architecture in New York City as part of the month-long celebration Archtober.  The exhibition explores how critical choices and consumption patterns of professionals and building occupants can make positive energy changes in our cities.  Shepard Hall was selected as an exemplar of sustainability in historic reconstruction.  his is particularly evident in considering the use of Glass Fiber Reinforced Concrete (GFRC) as the primary reconstruction material, in lieu of other materials.

The project’s 72,000 units of replicated terra cotta – the largest terra cotta replacement project in the world – yields an embodied energy savings by using GFRC of approximately 29,880,000,000 Btu or the equivalent of about 207,000 gallons or about 4,900 barrels of #6 oil when compared with cast stone and approximately 57,600,000,000 Btu – the equivalent of about 400,000 gallons or about 9,500 barrels of #6 oil – when compared with terra cotta.

In addition, in considering just the energy savings in transportation of the much lighter GFRC, the 72,000 units of replicated terra cotta, the savings in the weight of material that must be fabricated, transported to the building, lifted and installed is 14,400,000 pounds – or 7,200 tons.

Here is how we arrived at the findings in savings. Information on the embodied energy of various materials is from the Handbook of Energy Use For Building Construction prepared for the US Department of Energy by Elemental’s Carl Stein and the late Richard G. Stein:


The analysis examines two alternative systems for replacing decorative, cast masonry units – thin shell glass fiber reinforced concrete and cast stone.  Cast stone is used for the solid alternative because there is limited embodied energy data available glazed terra cotta, the original material and, at other buildings on the CCNY campus, cast stone has been used to replace deteriorated terra cotta.  Note, however, that structural facing tile – a clay-bodied vitreous-glazed unit masonry product that is similar in composition to glazed terra cotta – has an embodied energy of about 860,000 Btu/ft3 as compared with that for precast concrete which is approximately 318,000 Btu/ ft3

The exterior reconstruction of Shepard Hall was the first large-scale use glass fiber reinforced concrete (GFRC) – thin shell units for historic preservation.  This greatly reduced the quantity and weight of the replacement cladding as well as achieving a number of technical goals such as accommodation of thermal movement

Currently, more than 65,000 damaged terra cotta units have been replaced.  When complete, the total will be approximately 72,000 units. As a frame of reference, GFRC (Glass Fiber Reinforced Concrete), with an average wall thickness of ¾” is compared with cast stone (precast concrete) having and average thickness on 6” including the complex molding and sculpture.

Embodied energy in precast concrete is 318,000 Btu/ ft3.

Average face area per unit is approximately 3 ft2

Volume of GFRC is 0.19 ft3

Embodied energy for GFRC is approximately 60,400 Btu/unit

Volume of cast stone is 1.50 ft3

Embodied energy for cast stone is approximately 477,000 Btu/unit

GFRC saves approximately 415,000 Btu/unit (average) when compared with cast stone.

Note: this does not include the embodied energy in the polymers and matakaolin that would be added to both materials, increasing the embodied energy savings for GFRC; however, it also does not include the Alkali Resistant glass fiber reinforcing (approximately 4½% of the total weight) which would apply only to the GFRC. If the embodied energy in the glass reinforcing is similar to that in conventional glass fiber, it would be about 6,500 Btu/pound or about 9,000 Btu per unit.  In other words, even discounting the fact that there would be significantly more polymer and metakaolin in the cast stone, the addition of about 9,000 Btu of reinforcing results in the saving of about 415,000 Btu of concrete

The 72,000 units of replicated terra cotta for the entire project yield an embodied energy saving for GFRC of approximately 29,880,000,000 Btu (the equivalent of about 207,000 gallons or about 4,900 barrels of #6 oil) when compared with cast stone.

Using the embodied energy for structural facing tile to represent that of glazed terra cotta gives the following analysis:

Difference in volume of concrete between GFRC and terra cotta is approximately 1.0 ft3/unit.  (The cellular construction of the terra cotta body allows it to made with somewhat less volume of material than with cast stone

Volume of GFRC is 0.19 ft3/unit

Embodied energy for GFRC is approximately 60,400 Btu/unit

Volume of terra cotta is 1.00 ft ft3/unit

Embodied energy for terra cotta is approximately 860,000 Btu/unit

GFRC saves approximately 800,000 Btu/unit (average) when compared with terra cotta

The 72,000 units of replicated terra cotta for the entire project yield an embodied energy saving for GFRC of approximately 57,600,000,000 Btu (the equivalent of about 400,000 gallons or about 9,500 barrels of

#6 oil) when compared with terra cotta

Weight of Materials:

Although not directly convertible to energy quantities, it is also instructive to consider the weight of materials that must be handled in the reconstruction process. At 1.5 ft3/unit, the average cast stone unit weighs 225 pounds. At  0.19 ft3/unit, the average GFRC unit weighs 28 pounds. The weight saving for GFRC when compared with cast stone is +/- 200 lbs/unit.

For the 72,000 units of replicated terra cotta, the savings in the weight of material that must be fabricated, transported to the building, lifted and installed is 14,400,000 pounds – or 7,200 tons.

Carl Stein to Deliver Keynote Address at GRCA International Congress – Istanbul

Tuesday, August 30th, 2011

Elemental Architecture, a firm recognized for its pioneering work in sustainable architecture, design and advocacy is pleased to announce that founding principal Carl Stein, FAIA will be delivering a keynote address at the 16th International Congress on GRC in Istanbul, Turkey on September 6, 2011.

The four-day conference brings representatives from twenty nations to share knowledge and advancements in glass fiber concrete technology. Keynote presentations by Elemental Architecture, New York and Foster and Partners, London.

Construction Update: Shepard Hall TSRU Models

Wednesday, March 31st, 2010

Fabrication has begun of the models needed for the production molds for the thin-shell replicas that will replace the deteriorated terra cotta. Together with the previous nine phases, more than 60,000 pieces have been replaced making this by far the largest historic reconstruction of its kind in the world.

The thin-shell approach was developed in 1986-87 by Elemental (then The Stein Partnership) as a means to rebuild the failing structure on an accelerated schedule and still allow for a cladding that accurately reflected the original material.

At the project outset, more than one third of the original terra cotta had already failed and been removed to protect the public safety. As a result, many of the sculptural elements required either partial restoration or total recreation based on the surviving fragments and old photographs. Here, from the first phase (1986-1991) are original grotesques with missing heads, replicas awaiting installation and the rebuilt turrets with the new thin-shell cladding.




This process continues today. Because the contemporary manufacturing processes offer a much higher level of precision than did the original, care is taken to introduce the imperfections that are characteristic of the terra cotta. These include tooling marks, irregularities on flat planes and slight variations in the characteristic “white” color from piece to piece. Depending on the level of deterioration of the original terra cotta, the process of obtaining models can vary from the direct use of terra cotta originals as new molds, to partial reconstruction of damaged terra cotta and fabrication of complete recreations based on historic photographs and interpolations from other similar pieces on the building.

Here, models have been fabricated based on typical profiles found throughout the building


In other cases, terra cotta that had suffered minimal damage serves as models, such as these florettes


This unique grotesque from the building, missing pieces of his nose and and fingers, was carefully removed from the building


and restored to serve as a model for the new GFRC replacement.


When the models are finished, rubber-lined production molds will be created. The thin shell replacement units (TSRU) are then fabricated using a sprayed glass fiber reinforced cementitious system, about three quarters of an inch thick. The description of the process will continue as the project progresses.

Stay tuned for continued updates from the field.

Construction Update: Shepard Hall Entry Ramp & Facade Work

Thursday, February 18th, 2010

Entry Ramp Takes Shape


Central to the entry redesign is the reconstruction of the original ground floor entrance. In addition to the salvaged schist stone wall, concrete retaining walls form the stair opening leading

down to the original lower level stone arch entry.  Earth and gravel fill are compacted to serve as a supporting base for the new concrete stair slab.

Facade Reconstruction Underway


Scaffolding has been erected and selective demolition & removals have begun on the main building. The first step of the facade reconstruction is the selective removal of existing terra cotta sculpture to serve as models for new Glass Fiber Reinforced Concrete (GFRC) replicas.


A rigorously tested thin-shell GFRC, strong, light weight and durable, has been the material for all the terra cotta reconstruction. The entire reconstruction, totaling over 65,000 pieces, is currently the

largest GFRC reconstruction project in the world.

Following careful removal of the representative sculptural pieces, demolition of the remaining terra cotta will begin.

Steel lintel Investigation

Meanwhile, the demolition of the existing terra cotta window surrounds exposes the original steel lintels that support the window openings. Each steel lintel is inspected to determine its structural viability. Where possible, salvaging the original steel is preferred.


Schist Stone Sounding

Local Manhattan Schist stone is the primary façade material of Shepard Hall as well as the other campus buildings originally designed by George Post.  Through a process called “sounding,” each stone on the building is struck with a mallet and the sound produced is an indicator of the stone’s integrity.  Stones that sound “hollow” or are visibly damaged or deteriorated are marked by the design team for replacement.


Stay tuned for continued updates from the field.

CUNY Video: Preserving the Past, Building for the Future at City College

Friday, April 20th, 2007

Architect George Post’s neo-gothic confection at City College “would be almost impossible to

conceive of today,” says architect Carl Stein, who recently completed a two-decade restoration that uses modern technology

and materials while remaining faithful to Post’s artistic vision. The University celebrated the centennial of Post’s collection of buildings in 2007.