High Performing Buildings - Winter 2009 - (Page 42)

tenant space are air conditioned by several multizone AHUs with electronic modulating chilled water valves and staged electric heat. Chiller Control minimizes energy Consumption A direct digital control system orchestrates the air-conditioning sys- ElEctricity UsE Month october 2007 november 2007 december 2007 January 2008 february 2008 march 2008 April 2008 may 2008 June 2008 July 2008 August 2008 september 2008 total kWh consumption Approximate kWh/ft2 per year Approximate Btu/ft2/year kWh* 1,096,623 1,055,106 991,490 1,097,593 1,120,435 1,071,678 1,137,318 1,078,333 1,144,501 1,233,870 1,256,748 1,251,101 13,534,796 tem’s chiller controls. The BMS monitors the temperature of chilled water leaving and entering the system to determine cooling load. The system can then stage or automatically sequence the chillers on and off to meet cooling load demand. By adding or subtracting chillers from the run sequence as the load changes, the system optimizes the number of chillers required to meet the building’s actual cooling load while minimizing the central plant’s energy consumption. This feature allows for adjustments due to occupancy and weather and determines the most efficient time to start cooling individual floors to achieve a comfortable temperature at occupancy time. 5 Houston Center has three chillers: one 300-ton unit and two 800-ton units. Running a minimal number of chillers reduces operating costs. The 300-ton unit is used during low cooling load conditions to further enhance energy savings. A Breath of fresh Air Fresh air is brought into the building to ensure that indoor pollutants are diluted via an outside air-handling unit. This unit filters and preconditions the outside air according to the season, using heating and cooling coils. The outside air intake system is designed to deliver 70,000 cfm of fresh air to the building, equating to 20 cfm per person based on an estimated maximum occupancy of 3,500 people. (ASHRAE’s estimated maximum occupancy is seven persons per 1,000 square feet of net occupiable space.) Historically, porous fiberglass insulation matting has been used to line the ductwork of air-conditioning Winter 2009 systems and to provide thermal insulation and sound attenuation for the interior of AHUs. However, these porous surfaces provide favorable conditions for microbiological growth when they become damp and activate any dirt that may have become lodged in the insulation. The building’s systems are designed to minimize the exposure of conditioned air to porous insulation surfaces. This, combined with routine maintenance of the AHUs and air filters, enhances indoor air quality for building occupants. 5 Houston Center’s AHUs feature double-wall construction that encases the insulation between the inner and outer casing, taking the insulation out of the airstream and providing a smooth interior surface that is easily cleaned during routine maintenance. The air is distributed to the terminal boxes through externally insulated sheet metal ductwork that prevents conditioned air from coming into contact with fiberglass insulation. In addition, the AHU condensate drain pans are sloped in two planes to promote positive drainage of condensate water, which eliminates another challenge to indoor air quality. energy efficiency 5 Houston Center initially earned the U.S. Environmental Protection Agency’s ENERGY STAR® designation in 2005 and received the label again in 2006 and 2007. The EPA’s national energy performance rating system provides a 1 to 100 scale that helps organizations assess how efficiently their buildings use energy relative to similar buildings nationwide. A building that scores a rating of 75 or higher is eligible for the ENERGY STAR, a mark of 23 79,525 *gross kWh consumption includes: Tenant submeters garage lighting Tenant after-hours HVAC request 42 HigH Performing Buildings

Table of Contents for the Digital Edition of High Performing Buildings - Winter 2009

High Performing Buildings - Winter 2009
Contents
Commentary
OHSU Center for Health & Healing
Documenting Performance
Cook+Fox Architects Office
5 Houston Center
Skanska's Atlanta Office
Advertisers Index

High Performing Buildings - Winter 2009