Building renovation gives valuable artifacts a new home
Controlling the environment
One of the team’s major challenges was creating a workable environmental control system for the building. Most buildings are designed for a limited range of climate zones. In this case there were offices, a café, meeting rooms, and workshops, but those just needed to be kept comfortable for humans. In the building’s archival areas, it was a different story. Most of the areas didn’t require any extreme temperatures or humidity levels, though one section did have to be kept at 52 F and another at 26 F. But even in the rest of the warehouse the temperature and humidity must be tightly controlled. For example, the permitted humidity range is far narrower than that allowed under AHRAE 55-2010: Thermal Environmental Conditions for Human Occupancy. Instead of allowing up to 80% humidity with no minimum, the Smithsonian required humidity to be kept at 50% +/- 5% year round. This wasn’t for human comfort, but to protect the artifacts.
“The majority of the warehouse is one climate zone, with a standard humidity and temperature we dictate for the collections,” said Evi Oehler, project manager for the Pennsy Collections. “We have to avoid wide swings in the humidity. If it swings up and down, the materials will expand and contract, damaging the artifacts.”
Maintaining the humidity levels constant in all areas eliminated the risk of higher or lower humidity air leaking from one collection area into another. In some areas, however, the air did need to be kept separate. For example, some of the shops had dust collection systems that vented to outside collectors. Others had paint booths or soldering areas with Nederman snorkel exhaust units to remove the fumes. Some specialized labs required once-through air systems.
“There were a lot of specialized areas, each with its own climate control,” said Don Posson, managing principal engineer from Vanderweil for the project. “We really wanted to keep the climate zones separated so there wouldn’t be any cross contamination.”
The library and rare book collections also needed their own climate control. In this case, Posson said the system had to be in accordance with the National Archives and Records Administration’s policy directive covering Archival Storage Standards (NARA 1571). Among the Section 1571.8 requirements:
- Archives storage areas, processing areas, and preservation laboratories must be served from separate HVAC systems.
- The records storage areas of the facility must be kept under positive air pressure especially in the areas adjacent to the loading dock.
- Areas where records are used, processed, stored, or exhibited must be isolated from sources of pollutants and particulates, such as the loading dock, machine rooms, or areas where woodworking or painting take place.
Section 1571.9 covered the temperature and humidity, restricted daily temperature fluctuations to 5 F and/or 5% relative humidity. Paper records and most other artifacts have a maximum dry bulb temperature of 65 F, while some photographic media need to be stored at 35 F and 35% RH +/- 5%. The paper records were allowed a broader humidity range of 35% to 45% +/- 5%, though the preference is to maintain it closer to the 35%.
While there were a large number of air handlers, the building was able to get away with a single humidification system. Initially the warehouse was going to use a boiler, but this would have been too costly. Instead, the team went with a high-pressure fog system from Mee Industries of Irwindale, Calif., which is cheaper to operate and easier to maintain.
“The Meefog system is more energy efficient, especially for a building that is getting humidification throughout the greater percentage of the year,” said Posson. “We originally were moving in the direction of a steam boiler system and steam injection, but the Smithsonian brought up that they were going to be spending a lot of money on utilities, so we looked at fog as an option to keep the operational cost down.”
This Meefog system built for the Pennsy warehouse uses a redundant pump skid to pressurize the water and sends it through 2400 ft of high-pressure stainless tubing to 15 separate duct-mounted stainless steel humidification chambers. The pump can provide up to 540 lbs. of water per hour to arrays of impaction pin nozzles within those humidification chambers. The water passes through a .006 in. orifice in the nozzle and then strikes the impaction pin, which splits the water stream into billions of minute droplets that rapidly evaporate in the airstream. Solenoid valves controlled by the building management system open or close as needed to control the water flow to the nozzles, providing the exact amount of humidification needed at that moment in time.
Although the schedule was tight, the team did get the job completed in time. Some tuning was needed on the air handling systems to control the air pressure differential between different zones and prevent cross contamination. The museums started moving their collections into the new facility in August before their existing leases expired that fall.
For now, the museums have a beautiful new space to store and restore their artifacts and ready them for display. But even though the place is huge, it won’t be big enough for long. Oehler is working with the different groups to maximize the space they have, but the warehouse is filling up.
“We don’t get rid of things and our needs grow constantly,” she said. “As we grow, we will fill this place up to the rafters.”