Historic Government Building Fitted With Modern Snow / Ice Melt System
"Sandstone buildings may look indestructible," says Mark Euteneier, president of KLIMATROL Environmental Systems in Brampton, Ontario. "But the stone is actually susceptible to a number of elements. Acid rain, salts, other snow melting agents and countless shovels chipping it, all erode the stone and mortar. As a result, the front of the building was deteriorating, and the stairs were working loose."
In 1994 to 1995, the Ontario government replaced the stairwell, ramps and landing for both safety and aesthetic reasons. To delay the corrosive and damaging side effects of snow removal (both chemical and manual), the government and architectural firm on the project, Summit Restoration of Toronto, specified a hydronic snow and ice melt system (SIM) be installed underneath them. Before the installation could begin, both parties had to be convinced that a hydronic SIM system was appropriate. The building owner, Summit Restoration, consultant Marshal Macklin Monaghan and KLIMATROL commissioned an independent laboratory to conduct intensive testing.
Canadian Building Envelope Science & Technology (CAN-BEST) in Brampton, Ontario, provided facilities to test and measure
SIM system performance. The laboratory attached REHAU cross-linked polyethylene (PEX) RAUPEX pipes to the underside of a
5.5-inch-thick, 5-foot x 8-foot sandstone slab, using a proprietary heat transfer technique and materials developed by REHAU and
KLIMATROL. Twenty-eight thermocouples were placed on the slab to monitor its temperature. The slab was then cooled to 0°F
with a simulated wind. At 135°F, a mixture of 40 percent glycol/60 percent water was circulated through the pipes, and the slab's
temperature was recorded every 10 minutes. After 90 minutes, the slab reached the target temperature of 39°F.
System DesignApproximately 1,750 feet of 1/2-inch pipe, spaced at 6 inches on-center, was placed below the designated areas. The single-zone SIM system is connected to the building's central steam heating system supplied by Toronto District Steam Corporation. When the SIM system is engaged, steam is diverted from the District Steam heating loop into a stainless steel heat exchanger capable of supplying 150 Btuh per square foot.
The glycol mixture exits the 12-valve manifolds at 135°F and returns at 110°F. A REHAU outdoor sensor monitors the ambient air temperature, causing the system to engage when the temperature drops to 44°F and maintains the affected area at a constant 39°F.
"Using a temperature rather than a moisture sensor to activate the system greatly increases the system's response time," Euteneier
explains. "Although the system engages even in the absence of moisture, maintaining the affected sandstone at 39°F reduces
freeze/thaw cycles for the delicate sandstone slabs. Conversely, a moisture sensor allows precipitation to accumulate before
engaging. This causes congestion in critical pedestrian pathways, and dissipating the snow and ice ultimately requires more
energy than if the sandstone were partially heated prior to precipitation. In other words, we opted for a lower-output system that
engages more frequently than a higher-output system that has rapid melting capabilities but engages after accumulation begins."
System InstallationThe system was installed in November 1996 by contractor Aggett Ltd. of Toronto, Ontario, in three days using a three-man crew.
The sandstone slabs rest on ten 12-inch x 16-inch poured concrete beams. The SIM pipes were then attached to the sandstone's underside, passing under the slab and through holes in the beams. Proprietary heat transfer plates surround the underside of the pipe between beams to conduct heat to the full surface of the slabs. Using the heat transfer plates increases system efficiency by about 30 percent. Three layers of extruded polystyrene (EPS), totaling approximately 4.5 inches, rest below the pipes. A 1-1/2-inch galvanized steel horizontal brace supports the insulation and piping.
"We're running a single-zoned glycol SIM system off the building's primary heating system," Euteneier explains. "In these instances, the installation is not overly complex. The hardest work is upfront in determining necessary load requirements and system configuration. Accurately calculating these requires experience and technical assistance from the manufacturer. Once the system is designed, installation should proceed apace."