In late 2000, the firm of Beyer Blinder Belle Architects & Planners, LLC, was commissioned to direct an extensive restoration project that began in October of 2004. Aging gutters and roof leaders had started to fail, and intruding water had damaged the plaster ceiling and stone-and-tile walls. The scope of the project included cleaning 70 years of accumulated grime from the usually inaccessible surfaces of the Temple's vast interior and restoring design elements to their original pristine condition. Important systems upgrades also were undertaken, most notably the addition of air conditioning and the enhancement of both lighting and sound.

To ensure that the space would remain in active use during the High Holy Days of 2005, the project was divided into two phases. Phase I involved scaffolding and restoring the western half of the Sanctuary as well as the Beth-El Chapel. Phase II extended restoration to the eastern half of the Sanctuary including the bimah.

Over the decades, the acoustic range of our enormous Temple organ, built by Federlein and Casavant, had diminished. The entire mechanism, consisting of tens of thousands of pieces, was disassembled for thorough cleaning. The rebuilt organ, restored to its former grandeur, underscores the vital importance of music in the congregation's spiritual life.

The cleaning and careful restoration of the Sanctuary's architectural surfaces required material-specific restoration methods. The stained-glass windows were removed, disassembled, cleaned, and re-leaded. The wooden pews likewise were removed and restored off site, and new custom upholstery was woven. The Beth-El Chapel ceiling, walls, bimah, metalwork, and pews were restored, as were light fixtures and walls in the Temple's Marvin and Elisabeth Cassell Fifth Avenue Foyer. The cleaning revealed patterns hidden for years under a patina of accumulated soot and dirt.

The ceiling restoration required the construction of a complex labyrinth of scaffolding high above the Sanctuary floor. With the scaffolding in place, previously unseen details came to light, such as the artists' original brush strokes, pencil annotations beneath the surface of the paint, and areas that were reworked to give the composition more depth.

The stunningly rich range of colors in the more than 50 marble columns, obscured by decades of dirt was revealed after cleaning. The correlation now is obvious between the color of the marble columns and the predominant color of the stained-glass clerestory windows framed by the columns.

New lighting and sound systems were installed. Lights were positioned in the ledges of the stained-glass gallery windows, and additional lamps were placed in the Chapel chandeliers to up-light the ceilings-reinforcing the original designers' intentions for the spiritual quality of the space and emphasizing its inherent sense of mystery, while subtly illuminating the architectural details.