Case Studies

Building Thermal Model

Building Exterior Envelope Parameters

  • Utilized Zero•Net PW2500 for the building energy model
  • 100% Vision Glass
  • 0% Spandrel Glass or insulation in spandrel areas
  • Vision glass SHGC selected to meet as closely as possible ASHRAE 90.1-2007 requirements
  • Wall performance is the curtain wall performance U-factor

Building Was Modeled In 2 Climate Zones

  • Zone 2 – Phoenix, AZ
  • Zone 5 – Boston, MA
Thermal Barrier
Zero•Net PW2500

Zero•Net PW2500

Proprietary fiberglass thermal barrier

Boston, MA ASHRAE
90.1-2007
Type 1
Center of Glass (COG)
U-factor=.247
Type 2
Center of Glass (COG)
U-factor=.117 
Glazing Assembly U-factor 0.45 0.30 0.182
Assembly Solar Heat Gain Coefficient (SHGC) 0.40 0.37 0.398
Glass as a percentage of exterior wall area 100.0% 100.0% 100.0%
Peak Cooling (tons) 192 181 171
Tonnage Reduction 5.7% 11.0%
Peak Heating (MBH) 2146 2140 1923
Gas Boiler (MBH) Reduction 11.4% 20.0%
Annual Energy Spend $126,060 $113,099 $105,518
Annual Spend Reduction 10.3% 16.0%
Phoenix, AZ ASHRAE
90.1-2007
Type 1
Center of Glass (COG)
U-factor=.247
Type 2
Center of Glass (COG)
U-factor=.114 
Glazing Assembly U-factor 0.70 0.30 0.179
Assembly Solar Heat Gain Coefficient (SHGC) 0.25 0.25 0.237
Glass as a percentage of exterior wall area 100.0% 100.0% 100.0%
Peak Cooling (tons) 186 156 143
Tonnage Reduction 16.1% 23.1%
Peak Heating (MBH) 1965 1728 1619
Gas Boiler (MBH) Reduction 12.0% 17.6%
Annual Energy Spend $95,282 $75,333 $69,144
Annual Spend Reduction 21.1% 27.4%
Thermal Modeling was performed by Optima Engineering, Charlotte, NC using Trane Thermal Modeling Software