Vitro Certified^TM Newsletter

KOI Sky Residences 

Energy Study from Mexico’s Second Tallest Skyscraper Translates Into Practical Knowledge for Vitro Glass Fabricators in U.S. 

Monterrey City, Mexico  

Introduction 

Whether they are specifying glass for the tropical humidity of South Florida or the blistering desert heat of Las Vegas, architects want building owners to know the products they choose on their behalf are aimed at optimizing return on investment. 

A recent energy performance study commissioned by Vitro Architectural Glass for the KOI Sky Residences (KOI Tower) in Monterrey City, Mexico, does just that. Based on three years of real-world energy and operational data collected from a 64-story glass tower in one of the world’s most extreme climates, this newly published energy performance analysis demonstrates definitively that an investment in high-performance glass products from Vitro Glass not only pays for itself many times over, but also gives architects an extensive palette of aesthetic options from which to fulfill their design vision.  

Energy Modeling and Performance  

Over the past decade and more, Vitro Architectural Glass (formerly PPG Glass) has commissioned several exhaustive energy modeling studies to quantify the energy and environmental benefits architects and building owners can realize when they specify advanced solar control low-e glasses for commercial buildings in various U.S. climate zones. 

Recently, the company went a step further. Rather than conduct theoretical energy modeling on a hypothetical building based on speculative climate data, Vitro Glass engaged a third-party energy efficiency and sustainability consulting firm to analyze three years of actual operating and performance data for KOI Tower. 

The study, which can be downloaded here, shows how the use of high-performance architectural glass on KOI Tower has paid for itself and continues to do so, according to the following four criteria:

• Economic profitability including initial investment costs for HVAC equipment; 
• Economic profitability related to ongoing operating costs; 
• Energy efficiency as quantified by HVAC-related energy consumption; and 
• Occupant comfort as measured by acoustic comfort; glare reduction, light dispersal uniformity and color; and overall thermal comfort and radiation. 

The Building 

KOI Tower is Mexico’s second tallest building, standing more than 900 feet tall with 64 stories of mixed residential and commercial office space. Due to its dry, hot and extreme weather, ASHRAE has designated the local climate zone as 2B. Despite its difficult performance environment, KOI Tower is one of the first buildings in Mexico to earn LEED^® certification from the U.S. Green Building Council (USGBC). 

The Glass 

KOI Tower façade is glazed with double-paned insulating glass units (IGUs) fabricated with one lite of Solarban^® R100 coating on an Optiblue^® glass substrate coupled with another lite of clear glass. In addition to delivering a solar heat gain coefficient (SHGC) of .20—which is below the mandated target for LEED^® certification in Monterrey’s climate zone—the configuration provides visible light transmittance (VLT) of 42 percent and an elegant blue-gray aesthetic that harmonizes with the surrounding mountain range and the region’s changing light conditions. 

Methodology 

To gauge the economic and environmental impact of the glass specification on KOI Tower, the consulting firm compared the performance of Solarban^® R100 Optiblue^® glass to four other glass systems, all with aluminum framing. The following software programs were used:  

• Trace 700 software, a Windows based program used to construct virtual buildings, calculate their air conditioning loads, and simulate their hourly operation;   

• The IESVE7 program by Integrated Environmental Solutions, Ltd., an energy simulation program used to measure thermal comfort, natural lighting, solar radiation and energy consumption to aid in the design of sustainable buildings.  

The firm also used the Comfort Zone Analytical Method described in the ASHRAE 558 Standard to measure and analyze the building’s thermal comfort. 

The table below shows the five glass systems selected for the study along with their physical, thermal and optical characteristics: 

Results/Findings 

The consulting firm compared the five glass systems using 12mm monolithic clear glass as a baseline because it represented the most basic glass system that could be specified for KOI Tower, considering its structural issues, architectural design and wind loads.  

It also calculated the investment involved in each type of glazing according to the cost of the glass type (including window frames) selected and the cost of air conditioning (calculated according to the tons of cooling capacity required) necessitated by that selection. 

• Initial Investment Savings 

Compared to the use of the Solarban^® R100 Optiblue^® glass system, the energy and environmental performance analysis show the owners of KOI Tower saved nearly $350,000 (U.S.) in initial HVAC equipment cost (compared to the cost of an HVAC system needed to support a façade composed of clear 12mm monolithic glass). 

• Ongoing Operational Savings  

Compared to baseline 12mm clear monolithic glass, the energy and environmental performance analysis showed the use of the Solarban^® R100 Optiblue^® glass system on KOI Tower is saving the owners more than $620,000 (U.S.) in operational costs. Over the typical 40-year lifespan of a building, that will amount to nearly $25 million (U.S.) in cost savings. 

• Thermal Comfort 

The energy and environmental performance analysis showed that Solarban^® R100 Optiblue^® glass provides 15.7% more hours of thermal comfort for building occupants compared to baseline 12mm clear monolithic glass. This finding confirms that higher SHGC and U-Values equate to fewer hours of occupant comfort without the support of air conditioning systems. 

• Glare control 

The energy and environmental performance analysis showed Solarban^® R100 Optiblue^® glass reduced glare areas by 13.65% compared to baseline 12mm clear glass, providing building occupants with better natural lighting comfort and preventing unwanted glare. 

• Emission Mitigation  

The energy and environmental performance analysis showed Solarban^® R100 Optiblue^® glass reduced the volume of GHG emissions resulting from electric power generation by more than 1,833 metric tons of carbon dioxide-equivalent (tCO₂e) per year. Over the life of the building, this translates to a reduction of 73,355 tCO₂e, which is equal to removing the atmospheric emissions of nearly 37,000 vehicles. 

In the final analysis, all the data prove that the Solarban^® R100 Optiblue^® glass system reduced initial construction costs due to the smaller HVAC system required to keep the building comfortable and resulted in a high-performance sustainable building that is generating ongoing energy and cost savings for its owners.  

For more information about Solarban^® R100 Optiblue^® glass, visit vitroglazing.com or call 855.887.6457. Click here to download a full copy of the KOI Tower energy study.