Window Retrofit Garners DOE Attention

The window retrofit system utilizes the existing window’s monolithic glass lite.hia, underwent a window retrofit.The window retrofit system utilizes the existing window’s monolithic glass lite.

400 Market Street, Philadelphia, underwent a window retrofit.

400 Market Street, Philadelphia, underwent a window retrofit.

Like hundreds of aging, high-rise buildings throughout North America, 400 Market Street in Philadelphia was in need of a major upgrade to help it compete with newer buildings in a hyper-competitive commercial real-estate market.

Now, the 12-story, 200,000-square-foot building is dramatically cutting energy use and increasing tenant comfort, while becoming a national model for the Better Buildings Initiative, a $4 billion partnership between private industry and the federal government that is focused on improving the energy efficiency of commercial office buildings by 20 percent by 2020.

Because of the energy savings associated with its unique window retrofitting project, 400 Market Street also is part of a $1.6 million U.S. Department of Energy (DOE) study to measure the potential that low-E retrofitting glazing systems have for improving the energy efficiency of existing commercial buildings.

Old Windows that Wasted Energy

While expansive windows and views are attractive selling points for any commercial building, older structures like 400 Market Street were typically constructed with single-pane windows. That makes them big energy wasters, according to the federal government.

DOE estimates that inefficient windows account for as much as 25 percent of a typical building’s heating load in cold climates and 50 percent of the cooling load in warm climates. Upgrading these windows on hundreds of high-rise buildings, such as 400 Market Street, particularly throughout the Northeast and Midwest, represents a significant opportunity to cut America’s energy use.

Certified installers place a newly triple-glazed window.

Certified installers place a newly triple-glazed window.

A Less Costly Solution

Built in 1972, 400 Market Street is one of the first buildings in the country to incorporate RENOVATE BY BERKOWITZ (RbB), a revolutionary window retrofitting system that converts old single-pane windows into highly efficient, triple-glazed insulating glass units, enabling owners to avoid the expense and disruption of traditional “rip-out-and-replace” window upgrade projects.

Carolyn Pfeiffer, property manager for Kaiserman Co., which owns 400 Market Street, said the RbB system was selected after her firm did extensive research into more traditional renovation alternatives.

“We were looking to upgrade the efficiency of the building envelope to help improve our ENERGY STAR rating, reduce operating expenses, and improve the comfort level for our tenants,” she explained. “We previously used window film, but it lost its effectiveness and was subject to scratching and color changes, and would only help keep the building cooler in the summer. It wouldn’t help keep the building warm in the winter. We also considered full window replacement, but the cost was prohibitive even without the supplemental cost of temporarily relocating tenants and disrupting their businesses.”

Pfeiffer said the RbB system helped mitigate all of those concerns. “The new system was about half the estimated cost of a traditional window replacement project and helped make us eligible for a tax deduction of up to $0.60 per square foot,” she explains. “The contractor was able to replace over 18,000 square feet of glazing (525 windows) in 50 working days, which was two to three times quicker than the estimates for the traditional replacement scenarios.”

The window retrofit was half the cost of a window replacement.

The window retrofit was half the cost of a window replacement.

Because 400 Market Street remained completely enclosed, occupants encountered minimal disruptions to their work areas throughout the retrofit project, which was another factor in deciding to implement the system. “Overall, our tenants were pleased with the installation,” Pfeiffer notes. “We were able to avoid the time, cost and hassle of temporarily relocating them. Now that the renovation is complete, we’ve heard comments about how much more comfortable the building is, and tenants on the lower floors have mentioned a decrease in street noise.”

As part of the renovation, Kaiserman Co. also installed a high-efficiency boiler system, and has reported a significant reduction in running times since the window retrofit was completed.

Attention from DOE

Given the potential of the RbB system to improve energy efficiency in high-rise buildings, 400 Market Street is serving as a research case study for the DOE. Although the DOE is monitoring the energy performance throughout the building, the agency is concentrating its technical analysis in two pairs of unoccupied offices facing different orientations—north and east. One room in each pair has been retrofitted with RbB while its twin will be left in its original, single-pane configuration until the end of the year-long study.

The DOE will use energy modeling data to compare actual energy consumption at 400 Market Street to pre-project projections and past usage. According to calculations made using the eQUEST energy simulation program, 400 Market Street is projected to save more than 25 percent in total annual energy costs.

“While our study has just started, preliminary observations are encouraging,” says Thomas Culp, project manager and independent DOE consultant.

“The RbB system made transforming 400 Market Street into an energy-efficient, competitive building a cost-effective reality,” Pfeiffer adds. “We anticipate the renovation will be a key factor in retaining and acquiring tenants.”

About the System

The window retrofit system utilizes the existing window’s monolithic glass lite.hia, underwent a window retrofit.

The window retrofit system utilizes the existing window’s monolithic glass lite.


The Renovate by Berkowitz (RbB) window retrofit system is designed to utilize the existing window’s monolithic glass lite, eliminating the need to rip-out and replace the existing window. A factory made insulating glass unit is hermetically sealed to the existing glass lite from the interior of the building, creating a triple glazed insulating glass unit. A custom formulated warm edge spacer is used to hermetically seal the new unit to the existing glass for a permanent installation. The warm edge spacer is desiccated to absorb any ambient moisture between the new and existing glass, eliminating any additional cleaning maintenance.

The factory-made insulating glass unit portion of the system features Cradle-to-Cradle-certified lites of Solarban Low-E glass by PPG. In addition, a second lite Low-E glass with PPG Sungate 600 is offered.

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