Post Oak Central office campus
The Post Oak Central office campus consists of three buildings, three garages and multiple small retail spaces on a 17.3-acre campus located at 2000 Post Oak Boulevard in Houston Texas. Post Oak Central Building 1, built in 1974, has a gross building area of 392,212 square feet over 24 floors. Post Oak Central Building 2 has a gross building area of 429,270 square feet over 24 floors, and was built in 1980. Post Oak Central Building 3, also built in 1980, has a gross building area of 445,511 square feet over 24 floors.
In general the buildings are in excellent condition and are very well maintained and operated. The energy use index (energy use per square foot) of the buildings is on par with similar buildings.
In spite of the efficient operation of the building, this preliminary energy audit resulted in identifying several low-cost/no-cost energy savings measures and has identified some potential capital improvement measures that should be evaluated further. These are listed in the tables below and described within the report.
The EUI of these buildings is 102.4 kBtu/ft2/yr in POC-1; 102.7 kBtu/ft2/yr in POC-2; and 73.4 kBtu/ft2/yr in POC-3. Typical energy use for office buildings located in the East South Central region of the United States is approximately 103 kBtu/ft2/year. While this comparison indicates that Post Oak Central is near the average EUI, it should not be taken to mean that there is no room for improvement.
EE&D engineers identified 5 Low Cost / No Cost Measures and 8 Capital Improvement Measures. Added together the overall annual kWh reduction is estimated at 287,253 saving approximately $1,030,521 per year. The total estimated cost of the identified measures is $7,086,740 with a simple payback of 6.9 years.
POC-1 has three chillers: two original Carrier centrifugal chillers of 700- and 650-ton capacities, and one newer Trane screw compressor of 350-ton capacity that was added in 1999. The Trane unit is used for winter cooling and other low-load conditions. The two main chillers are installed in a reverse series arrangement with the return chilled water entering chiller #1 and leaving chiller #2, and the return condenser water entering chiller #2 and leaving chiller #1. There are two 665-ton Marley cooling towers on the chiller system with 50-hp fan motors. These motors are on variable frequency drives (VFDs) and were installed in 1999.
Hot water for heating at POC-1 is provided by one 7,000 kBtuh Ajax gas-fired hot water boiler. There are two 40-hp 1,010 GPM chilled water pumps and two 40-hp 1,000 GPM condenser water pumps, and two 7.5-hp 138 GPM hot water pumps.
POC-2 has three 450-ton Carrier centrifugal chillers, which were installed in 1978 and are original to the building. Three 500-ton Marley fiberglass cooling towers were installed in 1994, each with a 25-hp fan motor. The cooling tower fan motors are on VFDs. There are also three 40-hp, 575 GPM chilled water pumps, and three 40-hp 1,270 GPM condenser water pumps, and two 15-hp 400 GPM hot water pumps. Hot water for heating is provided by two 7,000 kBtuh Thermo-Pak gas-fired hot water boilers.
POC-3 has three 450-ton Trane centrifugal chillers, all of which are original to the building. There are two new 690-ton BAC cooling towers on the chiller system, with 40-hp motors that were installed in 2009. The cooling tower motors are on VFDs.