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Student sitting at table
Study area
Overhead piping services
Overhead piping services
Removal of air handler
Removal of air handler

Showcase Project: Jessie Ball duPont Library HVAC Retrofit

Sector Type

Education

Location

Sewanee, Tennessee

Project Size

130,000 Square Feet

Financial Overview

$1.25 Million

Annual Energy Use

Baseline (2015)
116 kBtu/sq. ft.
Expected (2017)
81 kBtu/sq. ft.
Actual
Coming Soon

Energy Savings:

30%

Annual Energy Cost

Baseline (2015)
$128,000
Expected (2017)
$90,000
Actual
Coming Soon

Cost Savings:

$38,000
Background

The Jessie Ball duPont Library was completed in 1965 and serves as the sole library for the University of the South. In addition to the traditional book stacks, the library offers office space, meeting rooms, computer labs, and a 24/7 learning commons to a student body of 1,800, as well as the wider local community.

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Typical for the time of construction, the original HVAC system included a dual-duct constant air volume (CAV) system for airflow, with 160 tons of water-cooled direct expansion conditioning for cooling and a gas-powered steam boiler (66 percent efficient) for heating. The dehumidification was never fully realized and the constant air flow resulted in high fan use for the designed ventilation standards. This system had been connected to direct digital controls (DDC) since 1992.

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Solutions

The University designed and constructed a 680.7 kW/ton central chilled water plant in 2000 (and added an additional 500.3 kW/ton in 2013) and has been expanding the building system loop systematically to include existing structures and new construction. Mechanical and technical upgrades, along with utilization of the central chilled water plant, will result in significant energy savings at the library – an anticipated 30 percent.

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Savings Measure

Costs

Notes

Interior piping to tie into campus chilled water loop $161,000 Exterior piping for expansion of chilled water loop was completed under another project. Allowed for removal of old, packaged HVAC units.
Air Handling Unit replacement $297,000

Trane Modular Climate Changer units (3) with variable frequency drives.
Trane CSAA size 66 – 34,000 CFM
Trane CSAA size 35 – 17,000 CFM
Trane CSAA size 21 – 11,000 CFM.

Boiler replacement $166,000 Two condensing boilers installed, sized at 1750 MBH each and with an estimated thermal efficiency of approximately 98%.
Variable air volume (VAV) boxes to replace CAV $93,000 Low profile Trane VAV boxes installed with hot water reheat coils. New 2-way modulating controls were installed at each heating coil. All heating coils are in the reheat position.
DDC and building automation system communication upgrades $162,000 Carbon dioxide (CO2) now monitored at the zone level for demand controlled ventilation strategy.
kWh monitoring $6,100 Setra Power Patrol building meter installed for real time electrical monitoring.

With the library retrofit project completed, the plant now serves 500,000 square feet – nearly one-third of the total campus square footage. The renovation was completed without disruption of library services.

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Other Benefits

Improved occupant comfort is realized with more consistent thermal comfort in all four library levels. True dehumidification is being achieved with reheat coils, creating better conditions for preservation of books and sensitive materials. The installation of CO2 sensors in the VAV zones will result in decreased fan runtime and long-term maintenance savings.

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While the central chilled water plant has not yet reached total capacity, additional load is expected and a satellite plant will be needed in the future. The design for this future plant was incorporated in the pipe sizing, electrical panels, and mechanical room’s physical space during this renovation.

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