ASHRAE Journal - December 2011 - 17

swings have dedicated UFTs controlled by space temperature and/or space CO2 concentration with unique sequences of operations to maintain CO2 concentrations with outside air volumes. These varying loads necessitated underfloor partitions to isolate them from the main plenum. As with the main spaces, swirl diffusers supply air to each room, and transfer air openings in the ceiling partitions connect to the general return air plenum.1 Telecom rooms are excluded from the main plenum by fullheight gypsum board walls. Conduits, CHW piping, and other shared utilities have thoroughly sealed penetrations to ensure plenum integrity. The many trades co-located in the underfloor plenum required extensive coordination prior to and during construction. Prior to construction, weekly coordination meetings were held with all trades. In these meetings, BIM software was used to find conflicts, which were reviewed by all members of the subcontracting team. Affected subcontractors resolved conflicts before the meeting concluded, eliminating an estimated 99% of all in-field interdisciplinary conflicts. This coordination helped maintain the integrity of the underfloor plenum. Because the underfloor was not solely used for air distribution, clearances needed to be maintained so as not to create impediments to airflow. Because of the UFTs serving multiple spaces, and the security requirements of the end user (many full-height walls were used), sealing the zone partitions below the floor was important to ensure proper interplenum pressurization. Depending on the penetration location and size, a number of plenum partition fillers were used, including acoustical caulk, fire caulk, foil-backed tape, and fire barrier pillows. After construction in an area was completed, underfloor inspections were conducted with the owner’s representative (U.S. Army Corps of Engineers [USACE]) and the contracting team. These inspections verified that the underfloor was clean of construction debris and that all penetrations were sealed in a manner appropriate for the penetration type and location. UFAD testing could not proceed until an owner’s representative had signed off on the area. This additional review helped ensure construction quality for long-term results of maintainability, as well as the short-term for test success.

Figure 1: Floor plan layout. the office spaces was 1 cfm (0.47 L/s) at 0.04 in. w.g. (10 Pa), therefore, the allowable Type I leakage for a plenum was 0.05 cfm per ft2 (0.25 L/s per m2) based on floor area. The test equipment used consisted of calibrated digital manometers with 0.0001 in. w.g. (0.025 Pa) resolution and data logging capability and adjustable orifice-type duct leakage fans. The fans had flex duct connected to their outlet. This flex duct was fed into the floor plenum through holes intended for the swirl diffusers. Foil-backed tape was used to secure the flex duct and seal the opening. The manometers were placed under the floor to monitor the underfloor pressure. This rig can be seen in the photo on the facing page. Each floor of the building tested has between four and seven plenums, depending on the full-height wall layout for each particular floor. Each plenum received its own calibrated duct leakage test equipment, and 60 data points measuring pressure were recorded in 15-second intervals. Trial and error showed that the further from the supply air inlet of the test rig to the measurement point, the more stable the readings become, more quickly. Therefore, to avoid turbulence from the incoming airflow, the metering location was at least 50% of the way across the plenum from the air inlet, as shown in Figure 1. Testing was performed for the entire floor at one time since all the floor’s plenums share a direct or indirect connection. Each plenum’s test apparatus and manometer were installed
ASHRAE Journal 17

Testing Procedure
Two different types of leakage tests were performed on this project: Type I and Type II.3 Type I leakage is defined as leakage out of plenums and into spaces that do not provide occupant cooling. This leakage does little to contribute to occupant comfort and ultimately wastes energy. Per owner’s requirements, the allowable leakage rate for Type I was established as 5% by volume. Type II leakage is defined as leakage out of the plenum and into the zone being served (i.e., leakage through the RAF assembly) and is not necessarily detrimental to comfort heating and cooling. The allowable leakage rate for Type II was established as 10% more than the Type I leakage. For example, if a plenum had a Type I leakage rate of 3.1%, the Type II allowable leakage would be 13.1%. Both Type I and Type II were tested at 0.05 in. w.g. (12.5 Pa). The basis of design for
December 2011



ASHRAE Journal - December 2011

Table of Contents for the Digital Edition of ASHRAE Journal - December 2011

ASHRAE Journal - December 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Testing for Leaks in Underfloor Plenums
Optimizing Design & Control of Chilled Water Plants, Part 3: Pipe Sizing and Optimizing ΔT
Performance of Combination Hydronic Systems
Data Center Environments: ASHRAE’s Evolving Thermal Guidelines
Technology Award Case Studies:
Beyond the Envelope
Medical Center Rx
Special Section
New Product Preview
Standing Columns
Emerging Technologies
IAQ Applications
Washington Report
People
Products
2011 ASHRAE Journal Indices
Classified Advertising
Advertisers Index
ASHRAE Journal - December 2011 - ASHRAE Journal - December 2011
ASHRAE Journal - December 2011 - Cover2
ASHRAE Journal - December 2011 - 1
ASHRAE Journal - December 2011 - 2
ASHRAE Journal - December 2011 - Contents
ASHRAE Journal - December 2011 - Commentary
ASHRAE Journal - December 2011 - 5
ASHRAE Journal - December 2011 - Industry News
ASHRAE Journal - December 2011 - 7
ASHRAE Journal - December 2011 - 8
ASHRAE Journal - December 2011 - Letters
ASHRAE Journal - December 2011 - 10
ASHRAE Journal - December 2011 - 11
ASHRAE Journal - December 2011 - 12
ASHRAE Journal - December 2011 - 13
ASHRAE Journal - December 2011 - Meetings and Shows
ASHRAE Journal - December 2011 - 15
ASHRAE Journal - December 2011 - Testing for Leaks in Underfloor Plenums
ASHRAE Journal - December 2011 - 17
ASHRAE Journal - December 2011 - 18
ASHRAE Journal - December 2011 - 19
ASHRAE Journal - December 2011 - 20
ASHRAE Journal - December 2011 - 21
ASHRAE Journal - December 2011 - Optimizing Design & Control of Chilled Water Plants, Part 3: Pipe Sizing and Optimizing ΔT
ASHRAE Journal - December 2011 - 23
ASHRAE Journal - December 2011 - 24
ASHRAE Journal - December 2011 - 25
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ASHRAE Journal - December 2011 - 32a
ASHRAE Journal - December 2011 - 32b
ASHRAE Journal - December 2011 - 33
ASHRAE Journal - December 2011 - 34
ASHRAE Journal - December 2011 - 35
ASHRAE Journal - December 2011 - Performance of Combination Hydronic Systems
ASHRAE Journal - December 2011 - 37
ASHRAE Journal - December 2011 - 38
ASHRAE Journal - December 2011 - 39
ASHRAE Journal - December 2011 - 40
ASHRAE Journal - December 2011 - 41
ASHRAE Journal - December 2011 - Data Center Environments: ASHRAE’s Evolving Thermal Guidelines
ASHRAE Journal - December 2011 - 43
ASHRAE Journal - December 2011 - 44
ASHRAE Journal - December 2011 - 45
ASHRAE Journal - December 2011 - 46
ASHRAE Journal - December 2011 - 47
ASHRAE Journal - December 2011 - 48
ASHRAE Journal - December 2011 - 49
ASHRAE Journal - December 2011 - Beyond the Envelope
ASHRAE Journal - December 2011 - 51
ASHRAE Journal - December 2011 - 52
ASHRAE Journal - December 2011 - 53
ASHRAE Journal - December 2011 - 54
ASHRAE Journal - December 2011 - 55
ASHRAE Journal - December 2011 - Medical Center Rx
ASHRAE Journal - December 2011 - 57
ASHRAE Journal - December 2011 - 58
ASHRAE Journal - December 2011 - 59
ASHRAE Journal - December 2011 - 60
ASHRAE Journal - December 2011 - New Product Preview
ASHRAE Journal - December 2011 - 62
ASHRAE Journal - December 2011 - 63
ASHRAE Journal - December 2011 - 64
ASHRAE Journal - December 2011 - 65
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ASHRAE Journal - December 2011 - 117
ASHRAE Journal - December 2011 - Emerging Technologies
ASHRAE Journal - December 2011 - 119
ASHRAE Journal - December 2011 - 120
ASHRAE Journal - December 2011 - IAQ Applications
ASHRAE Journal - December 2011 - 122
ASHRAE Journal - December 2011 - 123
ASHRAE Journal - December 2011 - 124
ASHRAE Journal - December 2011 - 125
ASHRAE Journal - December 2011 - Washington Report
ASHRAE Journal - December 2011 - 127
ASHRAE Journal - December 2011 - People
ASHRAE Journal - December 2011 - Products
ASHRAE Journal - December 2011 - 2011 ASHRAE Journal Indices
ASHRAE Journal - December 2011 - 131
ASHRAE Journal - December 2011 - 132
ASHRAE Journal - December 2011 - 133
ASHRAE Journal - December 2011 - Classified Advertising
ASHRAE Journal - December 2011 - 135
ASHRAE Journal - December 2011 - Advertisers Index
ASHRAE Journal - December 2011 - Cover3
ASHRAE Journal - December 2011 - Cover4
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