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| James G. Johnson Elementary School was ripe for retrofit. The result was a renovation project that combines the latest technology with energy efficiency. |
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Johnson Elementary
A state-of-the-art school building
 James G. Johnson Elementary School in Charlottesville, VA, was built in 1954. The 49,000 sq-ft brick structure consisted of a central office area, from which extended two classroom wings with a center corridor and a row of classrooms on either side. One wing was a single story; the other was on two levels.
The heating system consisted of two steam boilers, and steam-heated unit ventilators in each classroom. Each unit ventilator was equipped with pneumatic controls for temperature and ventilation management.
All the original lighting in the building was incandescent. Classrooms were equipped with a number of ceiling pendant fixtures, which utilized 2000-W incandescent lamps. The classroom lighting levels produced by this arrangement were less than satisfactory.
As was customary at the time the building was constructed, there was no air conditioning. This led to periods during spring and fall when the building became uncomfortable due to hot, humid weather.
The exterior wall of each classroom was largely filled with single-glazed windows which, on sunny days, improved the inadequate light levels, but also contributed to heat loss in winter and heat gain during hot weather.
While the basic structure of the building was sound after more than 35 years of wear and tear, the Charlottesville Schools Capital Improvements Committee decided that the building should undergo a complete renovation of its mechanical and electrical systems, including the addition of air conditioning. The interior of the building was also to be spruced up with some minor floor plan changes, new floor coverings, and general redecorations.
The primary objective of the renovation was to produce a state-of-the-art school building using the latest learning resources, thermal comfort, lighting, indoor air quality, energy efficiency, and safety.
Plans and specifications for the renovation were prepared by architect Bond Comet, Westmoreland, and Hiner, with consulting engineer Simmons, Rockecharlie, and Prince, both of Richmond, VA. A general contractor was selected in July, 1992. The $2.6 million project was scheduled for completion in August, 1993.
Other Efficiency Measures
In keeping with the design objective of providing high energy efficiency, several major system components were selected: high-efficiency condensing boilers, variable-speed drives for pumps, automatic classroom lighting controls, and new insulated windows.
Boilers: Three 1 million Btuh high-efficiency modular boilers from AERCO International (Northvale, NJ) were installed along with an AERCO Boiler Management System. The system is controlled by the BAS and it, in turn, provides boiler status information to the BAS.
The boiler-management system is a sophisticated control method that starts and stops the three boilers and modulates their output to maintain maximum efficiency under various load conditions. The multiple boilers also provide diversity, so that the system can continue to operative under most condition even with one or two boilers down.
By M.R.Reese
Excerpted from Engineered Systems Magazine
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