Firm Provides Solutions for Humidity Problem
The major problem with the building is its age. Built in 1938, the 12-story structure is showing its age. The massive blocks of stone that comprise the building's facade have lost much of the mortar and as a result, the building leaks air through the cracks badly.
ENGINEERING ENTANGLEMENTSThere were also some serious engineering issues. In 1998 the Illinois Capital Development Board (CDB) had commissioned an engineering firm to completely revamp the HVAC in the building including the dehumidification system. Unfortunately, the whole HVAC system never seemed to work right, especially the critical dehumidification equipment.
Then in 2001 another engineering firm, GLHN Architects and Engineers of Tucson, Ariz., had just finished commissioning the Illinois Capital Complex chilled water system it had designed and built. The CDB asked the company to investigate the poor performance of the archives building's HVAC system and to make recommendations.
"The whole thing was a mess of both engineering errors and architectural problems," said Jim Kreutzmann, the GLHN engineer who led the project.
"There were clear errors in calculations that led to the HVAC system, including the dehumidifier, being undersized. The critical spaces, the vaults where the microfilm and paper records were stored, were not isolated from the rest of the building. There was even a tunnel to other buildings that was open and brought air into the archives. They were receiving the same air as the office area despite the fact that the vaults required 65°F dry bulb and 40 percent relative humidity to protect the documents and film, much lower than the comfort-cooled air supplied to the offices."
GLHN recommended the addition of partitions to isolate the vaults so they could maintain their own conditioned air under positive pressure.
"It was a big and expensive project," said Kreutzmann, "but the CDB recognized it was necessary to preserve the documents."
In addition to erecting partitions, they also installed automatic doors at the tunnel entrance and at the elevator lobby.
"These additions gave us the ability to control airflow," noted Kreutzmann. "Without that control, keeping the humidity at the desired level in vaults would have been impossible."
HVAC SYSTEM HORROR STORIESNext the company addressed the undersized HVAC system.
"The chiller was an easy fix," commented Kreutzman. "We simply installed a new York system that was big enough for the building along with additional piping. It was the dehumidifier that was a challenge."
The engineering team at GLHN had originally specified a large customized desiccant wheel system from Des Champs, but the proposed delivery time was too long for the CDB. Another dehumidifier manufacturer claimed they could meet the deadline and the CDB decided to go with them.
"The unit they proposed just wasn't right," said Kreutzmann. "It lacked capacity and wasn't reliable."
One main problem was that most desiccant wheel dehumidifiers use return air and heat to remove accumulated moisture from a desiccant wheel. In this case, since the building leaked air, 100 percent outside air was required for pressurization, so there was no return air. The unit would have to use outside air and that would require more heat than normal because the outside air would be more humid than typical return air would be.
"They proposed using low pressure steam as the heat," said Kreutzmann. "Their calculations were off. I tried to insist that they use high pressure steam, but they convinced the CDB that they were right and it was installed."
"It was a disaster from the beginning," said Tom Brady, head maintenance engineer for the Norton building. "First, they didn't make their deadline. Then the thing wouldn't work. It was wired wrong. They sent technicians to rewire the whole system on site. Then the compressors broke down. And then the desiccant wheel had to be replaced. Those things are supposed to last forever, but this one got overheated. Even when it was running right, it couldn't do the job."
In fact, to make up for the poor job the dehumidification system was doing, Brady and his team had to bring in consumer dehumidifiers, bought at a local department store, and place them around the vaults. For three years during each summer, one man's full-time job was to empty the water from these small units and when he was done, go back to the first one and start all over again.
DEHUMIDIFICATION TAKE TWOAfter all the problems, the CDB agreed that the only way to go was to replace the current dehumidification system with the one originally proposed.
Des Champs engineers got to work and developed a custom system to fill the unique needs of the Norton Building.
"Most desiccant wheel systems precondition air for the air conditioning unit to remove the burden of dehumidification and increase system efficiency," said Larry Borges of Climatec, the representative of Des Champs in Tucson. "This configuration was unusual because so much outside air was required to replace that which leaked out of the building. The York units cooled and recirculated the air in the building and the Des Champs unit dumped dehumidified outside air directly into the building."
The customized Des Champs dehumidifier uses conventional refrigerant-driven air conditioning coils to pre-cool 100 percent outside air prior to its passing through the desiccant wheel and removes some of the moisture.
The wheel itself is honeycombed and coated with silica gel, an adsorbent material that wrings most of the water out of the air, adding heat in the process. The air then passes through a postcool direct expansion system that brings it to a neutral 62° and releases it into the building where the floor-by-floor air-handling units condition and circulate it.
In the winter heating coils in the unit, using low-pressure steam, preheat the dehumidified air to the same temperature before releasing it in the building. In the sealed vaults the air handlers maintain temperatures at the desired 65° dry bulb and 40° relative humidity.
But dehumidifying all that outside air was where the Des Champs engineers made the difference.
"This is where pressure steam was needed," said Kreutzmann. "That's one place that the other system was improperly designed. Low-pressure steam couldn't provide enough heat for the dehumidifying process. The Des Champs engineers knew that and insisted that a separate high-pressure line be run. Now we had a dehumidification system that was big enough to handle the needs of the building."
"Everything is a lot better now," said Brady. "Even on the 12th floor right under the roof where the temperatures were up to 74° in the vaults with the old system, the air is as cool and dry as the specs say it should be. The Des Champs unit is great. It makes the building as dry as the Mojave Desert in just hours."
For more information, visit www.deschamps.com.
Publication date: 08/07/2006