Dry And On Time
August 1, 2007
Record rainfall in November, gale-force winds in December, snow in January … Mother Nature pulled out all the stops last winter in British Columbia. That made humidity control all the more critical at the site for what will be the province’s largest and Canada’s only LEED Silver hospital. With a financial interest in project punctuality, the team engineered a formidable short-term solution to keep the work on track and the drywall from becoming wetwall.
Desiccant dehumidification systems have been around for many years and have been utilized in a number of different industries - everything from pharmaceutical manufacturing to supermarkets to meat packing plants. Desiccant systems use materials such as silica gel embedded in a rotating wheel to remove moisture from building air. These materials can be regenerated by a variety of heat sources ranging from natural gas-fired dryers to waste heat recovery systems.
Often, these desiccant systems are installed permanently in an application, since the need for dehumidification is ongoing. However, many other applications can benefit from temporary dehumidification, and “portable” desiccant systems can be the right answer in these instances. Temporary desiccant equipment is particularly valuable in new construction, where a dehumidification solution can produce overnight drywall drying times, eliminate delays in laying flooring systems over concrete, and provide acceptable conditions for workers.
A recent project that benefited from the use of temporary desiccant systems is the still-under-construction, 645,000-sq ft, five-story Abbotsford Regional Hospital and Cancer Centre in Abbotsford, BC, Canada. The general contractor on this job was interested in obtaining a drying system that would control interior conditions and accelerate the drying of building materials so the project could remain on schedule. This became of particular importance during the fall and winter months when the area received near record-breaking snow and rainfall, which created extremely high humidity. Thanks to the temporary desiccant systems, the humidity levels in the building were kept low and the project could continue on schedule.
Engineered solutionAbbotsford Regional Hospital, which is scheduled for completion in May 2008, has been a high-profile project since construction began last year. The 300-bed facility is the largest hospital in British Columbia and will house the first cancer treatment center that is fully integrated into a BC hospital. In addition, the $355 million project is the first major public-private partnership initiative in the British Columbia health care sector and is also Canada’s first full-scale hospital built to environmentally friendly LEED® Silver standards.
PCL Constructors Westcoast, Inc., the D-B partner for the construction of the facility, knew that completing the unique construction on time required a key component - precise humidity and temperature control during the interior finishing stage. “On a project of this scale, the construction schedule is critical,” said Daryl Campbell, one of PCL’s area superintendents for the development. “Plus, our firm had a financial stake in meeting the completion date.”
To ensure the project would stay on schedule, PCL needed to find an effective, unobtrusive drying system to control interior conditions while the hospital was still under construction. Because Munters had provided successful construction drying services for previous PCL projects, Gregg Lowes, industrial accounts manager for Munters Moisture Control Services (MCS) in Western Canada, approached PCL site personnel to offer assistance on the Abbotsford hospital project.
“If a building isn’t properly dried in high moisture climates, there is the potential for mold, because mold will propagate fairly rapidly on wet drywall,” said Lowes. “On this project, we needed to maintain very low humidity levels so the concrete floors, drywall, millwork, and paint could all be dried quickly and efficiently.”
There’s more to temporary dehumidification than just rolling in the equipment, plugging it in, and turning it on; it is an engineered system that requires a tremendous amount of coordination and engineering know-how. “We needed to design a system that would take into account the moisture loads from the number of people working there, as well as the moisture loads from the materials,” said Lowes. “We had to do some fairly significant engineering on this project to make sure that we had the right size capacity of equipment.”
Strategic planningThe type of temporary equipment used in an application is dependent upon several factors, including the power requirements of the equipment and the type of energy sources at the team’s disposal. “Based on the resources that were available to us, we found we could use a temporary natural gas supply and also temporary power for the dehumidification system,” said Lowes.
With those factors in mind, PCL and Lowes worked together to develop a strategic plan that called for deploying high-capacity desiccant dehumidifiers on the hospital’s rooftop while the conditioned dry air would be delivered through the facility’s mechanical exhaust ventilation system.
This plan ensured comprehensive air distribution throughout the structure without affecting the supply or return ductwork on the permanent HVAC system. As an added benefit, the design would require neither propane heaters nor temporary ducting or heating lines that could potentially obstruct the 450 construction personnel working inside and outside the facility.
“We basically had to configure three systems: there was the supply system for the HVAC; the return for the HVAC, which was a closed loop system; then there was a standalone bathroom exhaust system. The equipment was ducted to the bathroom exhaust system, because it had a pretty broad distribution across the facility and would not contaminate the HVAC system,” said Lowes.
An interesting twist to this application is the fact that a completely new line of desiccant dehumidifiers was to be inaugurated on the construction site: the new DHI-125-ESU, a 9,000-cfm system that operates on both natural gas and electric power. As Lowes noted, these were brand new units that came directly from the factory to the rooftop, so all the necessary initial adjustments and setups had to be completed on-site.
Desiccant systems are known for using a large amount of energy during reactivation, which is when a portion of the desiccant wheel is heated to reactivate the silica and drive off the moisture. These units utilize Munters’ new PowerPurge™ technology, which is an energy recovery option that improves performance by delivering air at drier levels, while using significantly less energy than traditional active desiccant dehumidification systems. “PowerPurge improves the efficiency by 20% to 30% in terms of its energy use,” said Lowes.
While there were numerous temporary equipment scenarios that could have been employed, the parameters of the project, along with the budget, resulted in the specification of nine DHI-125 units. The combined units delivered approximately 75,000 to 80,000 cfm of dehumidified air ducted through specially modified Reznor gas-fired, 400,000-Btu duct furnaces attached to each DHI-125 unit.
Installation in adverse conditionsThe nine dehumidification units and their corresponding duct furnaces were delivered to the construction site in November 2006 during the interior finishing and drywall installation stages of the project. A 100-ton crane hoisted all of the equipment onto the facility’s roof, and care was taken to ensure the units would not create too many point loads. Each unit weighs about 8,000 lb, so a full review of the roof was necessary to ensure it could hold all nine units without structural modifications.
Windstorms, rainstorms, and snow all made the installation a bit more complicated, but the equipment was successfully installed so that dehumidification of the five zones of the hospital could begin. Because the dehumidifiers were in excess of 600,000 Btu and contained gas-fired heaters, the equipment had to be commissioned once the installation was completed.
Close monitoring of the units continued throughout construction to ensure that interior conditions stayed between 22% and 24% rh and 65°F to 68°, which were the parameters set by PCL. These conditions allowed for the quick drying of compound mud for the walls, drywall, and other building materials, while protecting water pipes during the cold winter.
“We were often on-site just to make sure everything was working, and things weren’t interrupted,” said Lowes. “Because it’s an active construction site, there were all kinds of things that could go wrong, from somebody shutting off the power to shutting off the main gas valve, which happened several times. We had to make sure everything was running smoothly.”
During most of the construction period, the Abbotsford area experienced harsh fall and winter weather. It began with torrential, record-breaking rainfall in November followed by cold and gale force wind storms in December. In January and February, the area experienced substantial snowfall and periods of cold winter temperatures, with chill factors reaching -4° over a few weeks.
The amount of precipitation and inclement weather created sustained high humidity in the area, with levels oftentimes reaching 95% for days at a time. Through it all, though, the equipment held steady, maintaining both workable interior conditions as well as providing proportionate drying functions throughout the project.
“We were very impressed that the construction process was not delayed due to the extremely wet, humid and cold weather we experienced during those few months,” said Rob Ireland, general superintendent for PCL. “While production personnel working outside were dressed in parkas, those handling indoor tasks such as drywall finishing wore T-shirts.”
All the temporary equipment was removed in April when the building could rely on its own HVAC system to control the indoor environment. There’s no question that the properly engineered dehumidification systems were a huge benefit to PCL, which has met all the necessary deadlines in order to keep the Abbotsford Regional Hospital on track. ES
Sidebar: Cool Solutions to Summer EmergenciesAs summer temperatures rise, so do emergency situations caused by extreme weather conditions. Yet despite the variety of problems, the solutions share a common approach: cooling and dehumidifying the air with a spot cooling system.
Summer brings unexpected air conditioning system failures. Redundancy, or a temporary solution, can help keep operations running.
“I use a lot of temporary cooling for emergency calls or repairs,” said Kevin McSpadden, regional manager at DP Air in Phoenix (www.dpair.com). “A unit may go down, we need to do a repair and the customer doesn’t have redundant cooling, so we put MovinCool units in place. I’ve put in four or five five-ton units and ducted all the condensers out. We’ve done repairs, small intermediate distribution frame closets, single-unit failures,” he said. “We roll the unit in until the repair can be done.”
Moisture from excessive summer rains, floods, and hurricanes can devastate buildings with blatant physical damage, mold, and mildew. Extracting moisture quickly is critical. Ken Morello, national sales and marketing manager for TOPP Portable Air in Aston, PA (www.etopp.com), described the urgency. “Once spores set, you’ve got about 24 hours to prevent them from spreading.”
“We had one job on Marco Island in Florida after a hurricane came through,” Morello said. “It was a high-end luxury residential condo tower. They needed to remove all of the moisture and rebuild it,” which resulted in renting hundreds of MovinCool units. MovinCool’s Classic Series and Office Pro units remove moisture by dehumidifying. They can also be ducted to direct the waste heat to help expedite drying.
Hot temperatures and humidity also threaten food, from processing to purveying. Morello described how one of America’s most beloved cookies was in peril and how portable cooling saved it.
“That summer, the state had really high temperatures and humidity,” Morello said. “The permanent system at the manufacturing company was drawing in outside air, so the air they were drawing in was also humid. The permanent system was running at half capacity. As the cookies were coming off the line, going through packaging, the assembly line was shutting down. We used MovinCool units to spot cool the process, from packaging to shipping.”
Manufacturing isn’t the only food process threatened by heat and humidity. MovinCool units have come to the rescue of a chain of convenience marts, according to Morello. When heat rises, particularly in standalone stores, refrigeration and air conditioning systems are strained, often beyond capacity. Supplemental cooling can mean the difference between profit or perish.
Morello’s company also uses MovinCool spot cooling to help school districts in the summer. It’s a cost-effective way to keep kids cool without the expense and rigmarole needed to purchase or rebalance a permanent system.
No matter what the summer emergency, the solution is to keep it cool.