High Performing Buildings - Winter 2008 - (Page 9)

Photo © Timothy Hursley A raised floor system enhances comfort, flexibility and sustainability. The VAV system used on this project is also known as an underﬂoor air delivery system (UFAD). A raised ﬂoor, similar to those used in many computer rooms, allows air distribution as well as room to run network cables and other utilities. This system enhances energy performance by distributing the air while requiring little pressure. Additionally, the fan system in this building saves 72.6% of the energy required by the Standard 90.1 budget building. The UFAD system also gives control to each person and provides the highest degree of effectiveness in distributing ventilation air. The vertical pattern of airﬂow tends to capture heat and local contamination and take it directly to treatment instead of mixing it through the space ﬁrst as many other systems do. UFAD systems require a warmer air supply than standard overhead distribution systems. Typical overhead air-distribution systems require 55°F supply air because it is mixed with the warm air at the ceiling before making its way to the occupant sitting at his or her desk. To cool the occupied space, this UFAD system was designed to provide 62°F supply air at the ﬂoor diffuser. As the air heats up, it rises and returns to the UFAD units via an overhead return system. However, the warmer UFAD supply airﬂow doesn’t allow for dehumidiﬁcation at the UFAD units without the use of reheat, which was not an option. So, dedicated ventilation units were used for the outside air requirements and dehumidiﬁcation of the building. The overall size and footprint of the building led to a design that has one UFAD unit per ﬂoor on each end of the building for a total of eight UFAD units, and one ventilation unit on each end of the building for a total of two ventilation units. A single ventilation unit serves four UFAD units, providing all of the outside air to the mixing box of the UFAD unit. The outside air damper for the UFAD unit is controlled by the zone humidity sensor, zone CO2 sensor, and zone pressure sensor to maintain proper humidity level, CO2 level, and building pressure. The ventilation units use variable speed drives and critical zone reset to maintain the required airﬂow to each of the UFAD units. Critical zone reads the position of each control damper located in the mixing box of the UFAD units and adjusts the pressure so that at least one damper is 85% open and no damper is more than 95% open. Chilled Water Production System While the value of mechanical systems is a combination of ﬁrst cost, operating cost, maintenance cost and repair cost, the low-bid system of awarding contracts frequently results in selecting low ﬁrst-cost and placing the decision primarily in the hands of the contractor. For Heifer, a different procedure was used to give the decision to the owner and select on the basis of overall value. The design team solicited proposals from three manufacturers who furnished price, performance and maintenance data. A life-cycle cost analysis was performed on the three Water stored in the wetlands irrigates the site with little reliance on outside sources. Winter 2008 Photo © Timothy Hursley HIGH PERFORMING BUILDINGS 9

Table of Contents Feed for the Digital Edition of High Performing Buildings - Winter 2008

High Performance Buildings - Winter 2008 Passing On the Gift: Heifer International Headquarters Head of the Class: University of Florida’s Rinker Hall How Far Can You Go? Pearl River Tower The Proof Is Performance: How Does 4 Times Square Measure Up? Lighting the Way: Two Guilford County Schools Montreal’s Retail Example: Mountain Equipment Co-op® (MEC)

High Performing Buildings - Winter 2008

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