Windows in Retrofit

Replacement windows play significant role upgrading buildings for energy performance and aesthetics
Bethany Stough
April 29, 2015
Bronx, New York

The historic renovation of the 100-year-old BankNote Building required the installation of over 2,100 new windows in several combined configurations to fill 350 extra-large openings. Crystal Window & Door Systems fabricated horizontally ganged window systems to replicate the existing arch top windows in 22 of the building's 12-foot-wide masonry openings. Each of the hand-constructed brick arches varied slightly, requiring accurate jobsite measurements, extremely close coordination with the fenestration installer, and individual plywood templates.

Renovation is a growth market for the window industry, as building owners and architects realize the cost savings and performance benefits of replacement façade products. This trend is only expected to expand in the future. According to McGraw-Hill Construction’s 2013 Building Stock Database, only 1 or 2 percent of building stock in the United States is new each year. This leaves the retrofit and renovation market wide open for window and window wall manufacturers, as well as installers.

“The renovation side [of construction] is a multi-faceted area,” says Mike Niklas, manager of business development for J.E. Berkowitz. “Six to seven years ago, most architects wanted to do new construction. [But] the amount of renovate/retrofit opportunities are pushed by needing to upgrade. Energy codes are increasing, so as new buildings get built, how do you keep old buildings competitive with the new?”

As owners and architects increasingly look to renovation, they are seeking more cost-effective and sustainable window upgrade solutions that also meet demands for aesthetics and comfort.

Performance and comfort

Leading the list of demands for window retrofit systems is energy efficiency. In today’s construction market, local building codes often require energy efficient improvements for building project approval. Thus, manufacturers are developing products that can meet these requirements for use in retrofit projects, says Gary Flemming, window business manager for YKK AP America.

Building owners are dealing with poor building performance due to windows without thermal breaks or high-performing glass, as well as increased noise pollution in urban areas where the majority of building stock needing retrofits exists. One solution from manufacturers is the addition of interior access panels that offer "a cost-effective solution that dramatically improves the performance of an existing opening," Flemming says. "For example, a window with a U-factor value of 1.00 can achieve .50 U-factor value when an interior panel glazed filled with hard-coat low-emissivity glass at the interior surface is used. The same window can gain as much as 9 sound transmission class. These improvements can be gained without removing the current window and with minor disruption to the occupant.”

The bottom line for building owners considering whether to pursue new construction or retrofit is payback. “[Owners ask] ‘if I spend x dollars, where and when does the value come back to me—as energy cost savings, added value to building?’ Net asset value seems to be a big part of [renovation]. That’s the evaluation building owners are going through,” says Niklas.

Window manufacturers are also working to develop better performing complete window systems to meet both budgetary and payback concerns. Officials from Kawneer Inc., for example, say the company developed a window with the U.S. Department of Energy that can achieve an R5 rating. However, because not all codes require the stringent R5 rating, the company offers the OptiQ Ultra Thermal Windows with the option of adding or removing thermal features based on performance and budgetary requirements.

Closely related to energy performance is tenant comfort. Old, non-high performing windows can cause occupant discomfort—cold interiors in winter, warm interiors in summer, excess noise, sources say.

Fifteen to twenty years ago, window film was the solution for improving energy performance and occupant comfort in old buildings. “Now there are [other] solutions that are more effective and aesthetically pleasing,” says Darrell Cherry, project manager for Renovate by Berkowitz.

“In recent years we've seen jobs require new windows to meet specific acoustic test levels,” says Vincent Grieco, New York Area regional & technical sales manager for Crystal Window & Door Systems. “Replacement of old drafty windows with new, modern thermally efficient windows lowers energy costs and improves comfort for the tenants and owners.”

Buffalo, New York

“Because the building was an historic restoration, we were required to maintain the existing façade and original glass,” says Jonathan Morris, project architect for Carmina Wood Morris P.C. “At the same time, we wanted to update the building and improve its energy and thermal efficiency, while reducing street noise from the light rail line out front.” To retrofit the building’s 760 single-pane windows, the architect chose the Renovate Platinum Plus II system from Renovate by Berkowitz. The system adds two lites of high-performance, low-emissivity glass to the interior surface of the existing windows.


Customers are not only pushing for increased efficiency and performance. They also want more aesthetically pleasing options—windows providing a modern look, with minimal sightlines and updated finishes.

“The biggest driver of development in windows is meeting increasing aesthetic, often driven by historic concerns or tax credits, while meeting the changing codes,” says Bill Wilder, director of technical sales, Graham Architectural Products. “Owners and architects are more sophisticated and are demanding customization on each project…[including] elevated water resistance, ADA operation, better thermal performance, enhanced flashings or moisture barriers and sometimes very high acoustic performance.”

Aesthetics are paramount in historic renovations, which make up a large percentage of the window retrofit market. “Historic landmark project specifications and other visual requirements of landmark commissions or boards can be quite difficult to achieve with modern window systems,” says Grieco. However, Crystal, as well as other window manufacturers, offer options and accessories like applied grids, traditional putty-line-look glazing beads, historic panning systems, and custom color powder coat paint finishes to deliver “modern window performance while maintaining the visual integrity of the original property,” he says.

Sources also note the importance of customization for today’s retrofit customers. “In an effort to reduce cost and enable customization, operable windows are being replaced by fixed wall systems. This trend is driven by a desire for cleaner sightlines in retrofit and new construction,” Flemming adds. “A punched opening that historically contained many operable windows is now being retrofit with storefront and window wall materials with integrated muntins...In many cases these systems offer more design flexibility at a lower overall cost.”

Challenges and opportunities

Retrofit projects come with their own set of challenges, including the additional costs of closing surrounding city streets at the project site, and evacuating occupants from homes and businesses. Because increased disruption can occur during a rip-out-and-replace renovation, due to timing, noise and mess, today’s customers “want the replacement done without disruption to their home or business activities and they want it a very competitive price. Quite a challenge for our industry,” says Grieco.

Window companies have been addressing these challenges by developing systems that capitalize on the need for quick turnaround in a fully occupied, working environment. Grieco also notes that installation accessories and materials offered by window manufacturers, such as face flange frames, installation clips, snap trim, applied panning, caulk expanders, low-expansion foam, speed up and improve the quality of the installation. “This translates directly into lower costs and higher profits,” he says.

Window and window wall manufacturers are beginning to understand the demands of the market when it comes to designing products for the retrofit customer. However, knowing how to capitalize on the opportunity the market provides can be a challenge, sources say.

“In retrofit, [the process] is a little bit different,” says Niklas. “Building owners say ‘I know I need to do this, but how do I go about doing it?’ From a manufacturing standpoint, [the potential retrofit customer] becomes a very challenging customer to pursue. How do you get ahold of a building owner? [Retrofit] makes so much sense. It’s so simple. The biggest challenge is getting it in front of building owners.”

Window companies are also working to educate owners about the available subsidies and tax credits through local governments and energy service companies for upgrading existing buildings. Updated HVAC systems and lighting are the most straightforward and well-known energy improvement for commercial buildings; however, upgraded high-performance fenestration is becoming more recognized as an energy savings asset. In terms of subsidies, this can only help manufacturers and glaziers selling a fenestration retrofit job.

See also...

Retrofit Payback by the Numbers
Installation Tips for Glaziers

Stough is managing editor for Glass Magazine, and e-glass weekly. Write her at