In 2011 the new owners of the iconic Wrigley Building in Chicago initiated an extensive retrofit project of the 1920s landmark. The goal was to return to the original architectural design intent while improving the performance and usability of the space — all to attract new tenants.
The first stage of the project was to evaluate the existing condition of the building and identify where the greatest improvements could be made to reduce energy use, increase comfort and control air infiltration.
The analysis found that 41% of the building energy use and 32% of the building energy cost come from the building envelope. Replacing the windows and air-sealing the building envelope would:
- Save $276,000 per year in energy costs (27% savings)
- Reduce carbon emissions by 1,730 tons per year (22% reduction)
- Reduce the building’s energy use intensity by 41 kbtu/sf (37% reduction)
- Pay back in 15 years or better (lower payback possible using only incremental costs, via rebates/ incentives or via potential HVAC downsizing)
There were several benefits specifically identified with replacing the windows. The projected fast payback and decreased energy costs were achieved because the building had approximately 2,000 single-pane windows installed that were more than 20 years old. By replacing the current windows with new windows that had a higher thermal resistance, the improvement would bring the interior surface temperature of the glass nearer to room temperature. This approach included comfort as a variable for increasing energy efficiency. The analysis found potential to relax the thermostat set points by up to 5º F, delivering significant savings.
The second benefit of replacing the windows was eliminating drafts from leaky window units. Replacing the windows in this facility with new windows reduced drafts from the windows by 51%.
To satisfy the aesthetic goals of the project, only energy-efficient windows and doors that could match the original design were considered. Choosing high-quality windows that were also attractive provided the new owners with an enhanced image of the building that retained the historical feel. The concern for aesthetics as well as comfort allowed for a potentially higher property value and higher rental and lease income while reducing the maintenance costs and upkeep burden.
The Wrigley Building retrofit project required custom windows that would maintain the historical integrity of the building while providing an interior cleaning option for the owner. EFCO provided a custom version of their 690 double-hung windows (shown on bottom row in the picture) that utilized mortised auto-spring tilt latches, keyed sweep locks and a low-profile handle rail.