RetroWAL Interior Curtainwall Retrofit System

Energy Efficiency

Windows are the “weakest link” in a building in terms of temperature control and energy demand as significant amounts of heat flow out of buildings through poorly insulated glass and frames – yet often more focus is put on updating heating, ventilation, and air conditioning (HVAC) systems rather than dealing with the underlying insulation issues of the building’s windows.CrossSection

RetroWAL™ can reduce energy consumption by at least 20%, which lowers HVAC usage and utility costs:

  • Reduces thermal heat loss – the baseline RetroWAL™ Silver Series product triples the performance of existing insulated glass by regulating heat flow through the installation of a second piece of glass, which creates an air gap to prevent heat loss.  Upgraded RetroWAL™ Gold or Platinum product series systems can improve center of glass performance by 5 or 8 times.
  • Reduces air leakage – RetroWAL™ also improves the energy efficiency of existing windows by reducing air infiltration, lowering the amount of energy needed to maintain temperature. The air infiltration has been tested to .01 CFM per square foot of glass with RetroWAL™.
  • Reduces flow of infrared energy – RetroWAL™ uses low emissivity (Low e) coating on the glass, which improves insulation by minimizing the amount of ultraviolet or infrared radition that can enter or leave a building through the glass. This maintains temperature control while still allowing visible light in the room.


Thermolite created a building model study using the available information about the Exxon Building, more commonly known as 1251 Avenue of the Americas, from the City of New York Building Energy Database to show how our RetroWAL™ Silver Series interior retrofit window system would impact energy savings in large city commercial buildings with non-thermally broken, single glazed curtain wall. The results were applied to cities with varying climates throughout the US:

Window Retrofit Energy Savings









RetroWAL™ Energy Test Results and Reports:

URS Energy Analysis Report

625 North Michigan Avenue Tower Window Retrofit Test Results

TRACE 700 Test Results