Case Studies – Temporary Climate Solutions

Target Field construction at risk due to humidity

Climate control expert Polygon stepped up to the plate to assure that the high-end millwork that adorns the indoor sections of Target Field, the new home of baseball’s Minnesota Twins, will be a hit with fans when the ballpark opens.

Located in the historic Warehouse District of downtown Minneapolis, the 40,000-seat open-air ballpark will feature a natural limestone exterior, baseball-themed restaurants, state-of-the-art locker rooms, 54 private suites, and 3,400 club seats. Target Field also will feature one of the closest seating bowls to the playing field in all professional baseball, and a 360-degree open main concourse giving fans an uninterrupted view of the action. The ornate millwork, cabinetry, and high-end finishes in the lounges, clubs, bars, locker rooms, executive suites, and restaurants required special care during construction in 2009.


With summer approaching, Eric Keleny, MEP (mechanical, electrical, and plumbing) coordinator with M. A. Mortenson, needed a game plan for protecting sensitive indoor materials from high humidity and warm weather.

“The manufacturer had specifications for temperature and humidity for the wide variety of wood and laminate being installed,” said Keleny. “Extremes in the indoor environment could potentially expand or shrink the wood, causing warping.”

Understanding the severity of the conditions if not handled properly Keleny called Polygon to help control humidity and temperatures during the rest of the construction.


Keleny requested that relative humidity levels indoors remain below 50 percent and that temperatures remain below 80 degrees Fahrenheit. John Pfeffer, industrial accounts manager for Polygon, called up three 6000-cfm Humidity Control Units (HCU), in combination with several blowers for shipment to the site.

The HCU combines cooling and desiccant dehumidification technologies in one energy-efficient system to control dew point temperatures in hot, humid climates. It is ideal for use in structural drying, temporary humidity control in building construction, and condensation and corrosion control in surface preparation and coating applications.

“The HCU is capable of delivering dew points as low as 40 degrees Fahrenheit in even the highest humidity load conditions,” said Pfeffer. “Because the unit utilizes reactivation energy, it uses less energy while providing comfortable outlet temperatures.”

When the equipment arrived, accessibility presented a challenge. Using the ballpark’s inner field to reach the indoor spaces was not an option, the units were placed in small areas on different parts of the main concourse and flexible duct was used to move air to the inside of the building. Twelve 48-inch turbofans moved the air around the club-level spaces that required humidity control. The quick timeline of the construction project required that all systems be up and running in spaces that were ready for temperature control.

“We moved quickly to make sure indoor spaces were conditioned as millwork was installed in bar areas, administration offices, board rooms, executive and corporate suites and throughout locker room areas,” said Pfeffer.

In total, Polygon conditioned 150,000 square feet of the 500,000-square foot structure. Throughout the project, Polygon’s technicians periodically monitored conditions and handled maintenance work such as filter replacement. The ballpark was scheduled to open in time for the 2010 baseball season.


Improved Working Conditions

Lower temperatures made the environment more comfortable for workers, especially during the warm summer months. In addition, the dry air decreased the drying times of building materials as well as combatted mold growth. These extra benefits helped keep the construction timeline on “target” during these construction phases.

LEED Advantage

The Polygon HCU’s used on site also will help the contractor obtain a LEED point, assisting in qualification for LEED credits. The team also had access to certified LEED AP personnel to consult for any advice or questions. The units were used in conjunction with the permanently installed HVAC systems to flush out the building prior to occupancy, per LEED guidelines.

“Polygon stepped up to the plate to keep the high-end millwork safe from high humidity levels during the hot and humid summer and fall months, while keeping our workers comfortable,” said Keleny. “We are very pleased with the performance of the units, their easy installation, and the monitoring by Polygon’s technicians.”

For more about LEED certification and how it can help with climate control listen here.

Temperature and relative humidity readings are collected by Polygon operations technician to determine performance of the HCU-6000.

“Polygon stepped up to the plate to keep the high-end millwork safe from high humidity levels during the hot and humid summer and fall months, while keeping our workers comfortable.”

Eric Keleny, MEP Coordinator with M. A. Mortenson