End of the Era of Hanging Tubes: "Temporary" HVAC System to be Removed

The construction contractor has scheduled a crew to begin today to remove the old overhead tubes left from the library's “temporary” HVAC system. The process is to start on the south end of the 4th floor in the open stacks area of the Latin American Library (LAL) and then progress through the lower floors in sequence. The tubes that ran through the LAL closed stacks and the open general stacks on the north end of 4th floor have already been taken down.

A separate crew will be dispatched later, likely beginning next week, to follow behind and begin to replace interior transoms and repair other holes left from the tubes.

The temporary HVAC system with its interior air distribution tubes spanning each floor in eight locations was first installed in the initial effort to remediate the heavily damaged Howard-Tilton building after Hurricane Katrina.  The system was designed as an interim measure to last for a relatively short period of time; it served the library, for better or worse, for more than nine years.

The exterior work to remove the temporary HVAC towers, blower units, and chilled water lines along the back of the building will be treated separately, but this too is expected to commence within the next few weeks. That work will include the removal of the metal flange and damper pieces fitted into former windows and through which the tubes were connected to the outside towers. The windows have all been measured for new glass and they’ll be replaced as part of the tower removal, with precautions taken to limit brief interior exposure to the outside elements through these openings. Special attention will be paid to the scheduling of the work in areas such as the LAL rare and closed stacks areas on the 4th floor, classroom 309, and staff office areas.

Since the switch to the new permanent HVAC system two weeks ago, the new system has worked well in some areas of the building and not so well in others.  Some of the balancing the system may have to do with air picked up in the system that feeds some of the new cooling units from the campus chilled water supply. This may have caused some vapor lock in units that feed certain locations getting very little air on the lower floors. Technicians from the mechanical/electrical subcontractor MCC are bleeding all the lines to these units to remove any air that may have become trapped. After this they may be able to get a truer sense of which areas actually have air flow issues otherwise due to closed dampers. Also, yesterday a humidity issue on the north side of the 3rd floor was traced to to an open air vent in the graduate carrels nearby at the northwest corner of the building. The vent was designed to release building air pressure, but was heating that corner of the carrels with direct outside air. The wall in the carrels there does not extend to the ceiling so warm humid air was mixing with the new cool air in the adjacent stacks area, creating condensation. The vent is now sealed, and the humidity is dropping.

Monday, a team from MCC is scheduled to begin a more thorough inspection of the air duct and diffusers on each floor. The team will search for dampers that need to be manually reopened and other potential issues. They plan to start in the basement and work their way up through floors 1-6.