Vacuum Insulated Glass Improves Energy Efficiency of Historic Steel Windows

vacuum insulated glass

Steel windows were extremely popular in the U.S. in the late 19th and early 20th centuries for a number of reasons. The structural strength of steel allowed designers to create larger window openings while utilizing narrow profiles to maximize the visible glass in a typical opening. This also appealed to popular modernist architectural designs of the period that incorporated large expanses of glass with very narrow sightlines. Steel also has proven to be an extremely durable material that will last for hundreds of years with minimal maintenance.

The ubiquity of steel windows in historic structures can create a challenge for building owners. Although the design and durability of historic steel windows is a big asset for a landmark structure, it can also create a major challenge when it comes to bringing the structure up to modern energy-performance standards. Steel windows are inherently inefficient in thermal and shading coefficient standards, making them a liability to restore. There is, however, a new means to breathe life into these classic window designs.

Re-View Windows Inc., a full-service historic window company, recently performed steel window restoration at the John Sevier State Office Building in Nashville, Tenn.

Re-View Windows Inc., a full-service historic window company, recently performed steel window restoration at the John Sevier State Office Building in Nashville, Tenn. The Art Deco-style building was constructed in 1940 as the Tennessee State Office Building and now houses the offices for the attorney general and the Tennessee Highway Patrol command center. The full-scale renovation project involved exterior restoration of masonry and windows and a complete restoration of the interiors, including upgrading the mechanical and lighting systems.

The original steel windows had been neglected for decades and suffered from corrosion. The windows also failed to meet desired goals for energy efficiency. The simple answer to demands for energy upgrades in a building like this is to replace the windows with modern units. Given the historic significance of this structure, replacing the windows with an aluminum facsimile was not an option.

Re-View Windows confronts the balance of maintaining the historic integrity of an original window system with modern energy performance demands on most of its projects. As the country pushes for public and private buildings to meet a net-zero-energy consumption goal in the future, Re-View has had to get creative in upgrading the energy performance of its window restorations. The firm’s team members are very adept at making modifications to the design that don’t impact the historic architectural appearance. Re-View Windows’ steel window restoration of the John Sevier State Office Building is a fine example of its ability to achieve modern performance from period windows.

Re-View Windows confronts the balance of maintaining the historic integrity of an original window system with modern energy performance demands on most of its projects.

The Re-View Windows crews removed all of the window sash on the project and installed temporary enclosures. The sash were shipped back to the Re-View restoration plant where team members removed the existing glazing and finishes. Craftsmen restored the sash by welding replicated parts and structurally deficient sections. Re-View also filled pits with special restoration epoxy designed for steel. The sash were then blasted to achieve a targeted surface preparation for the specialty fluoropolymer finishes that were applied to all surfaces. The Re-View field crews restored the frames onsite before reinstalling the restored sash. Many of the sills needed to be replaced because of decades of corrosion.

In an effort to upgrade the energy efficiency of the window system, Re-View Windows glazed the windows with vacuum insulated glass (VIG). This glass, which already is widely used in Japan, is just beginning to gain popularity in U.S. commercial construction. VIG is created by extracting the air between two sealed panes of glass, creating a vacuum that has amazing insulating qualities. This vacuum technology is capable of achieving previously unthinkable energy performance, such as a 1.4 U-Factor. In addition to the outstanding performance data, VIG can be as thin as 6.2 millimeters, making it ideal for glazing historic steel window sash. Re-View glazed the VIG with putty to match the architectural design of the originals.

Vacuum insulated glass (right) versus a typical insulating glass unit.

Re-View Windows also restored the window hardware by removing finishes and varying degrees of patina. The crew then applied a patina that was desired by the design team. Broken or missing hardware was custom-casted to match the existing. Re-View Windows often has to custom- make hardware because the original manufacturers are no longer in business.

Re-View Windows’ steel window restoration at the John Sevier building is a fine example of gracefully connecting historic integrity with modern technology.

Retrofit Team

ARCHITECT: HFR Design, now owned by Wold Architects & Engineers

GENERAL CONTRACTOR: Hardaway Construction

WINDOW RESTORATION: Re-View Windows Inc.

Materials

VACUUM INSULATED GLASS: Pilkington Spacia from NSG Group

WINDOW SASH FINISHES: Tnemec

About the Author

Brooks Gentleman
Brooks Gentleman has a master's degree in business from Southern Methodist University and a bachelor's degree in economics from Colorado College. He comes to Re-View with 25 years of window experience.

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