Is radiant cooling right for your next project?

 

Have you considered exploring radiant cooling for benefits such as increased comfort, increased efficiency, leed credits, improved acoustics and reduced maintenance but been stymied by high first costs? Climate Mat by Viega provides radiant tubing in pre-configured and scalable modules — significantly reducing the labor and first costs associated with radiant heating and cooling projects.  Climate Mat was recently chosen for installation in several Wal-Mart stores, and may be an option for your next project.

 

The Wal-Mart solution

 

As part of its commitment to environmental sustainability, Wal-Mart has developed a line of high efficiency (HE) stores. The fifth generation prototype of this effort, an “HE.5” store, was opened in Las Vegas in March of 2008. Las Vegas’ hot, dry climate (iecc climate zone 3B) means moderate heating loads, large sensible cooling loads, low latent loads, and excellent potential for radiant cooling.

 

Wal-Mart set an aggressive goal of achieving 45% energy savings with the HE.5. Though many technologies and systems were employed to achieve this goal in areas such as lighting, refrigeration, and the building envelope, the radiant cooling system is the project’s cornerstone energy efficiency technology.

 

Wal-Mart’s HE.5 is a rectangular configuration divided into six discrete space conditioning zones. The refrigerated grocery zone has no cooling load, while the 81,500 ft.2 merchandising zone has a cooling load of 13 Btu/h-ft.2, and the 29,500 ft.2 of checkout area requires 30 Btu/h-ft2. Variable loads and infiltration requirements posed a challenge to engineers in their design and specification of a comfortable, affordable, and energy efficient system.  Traditional, air-only systems were considered but did not offer the performance of radiant cooling.

 

Radiant cooling innovation

 

Though radiant cooling was a perfect fit for energy performance, first costs were a concern. Value-engineering the radiant system was a top priority, and radiant tubing circuits were seen as a savings opportunity. A typical labor crew can lay and tie 1,000-1,250 linear feet of tubing per person in an 8-hour day. With approximately 200,000 linear feet of tubing, the man hours required for a traditional installation were cost prohibitive.

 

To provide an answer to budget challenges, the project team turned to Climate Mat, a scalable, pre-configured tubing module developed by Viega that could be installed quickly. Instead of manually laying, tying, and suspending individual lengths of tubing, Climate Mat enabled the installation contractor to simply roll out the tubing on the compacted gravel base and pour the 4" slab directly on top. Because the sections are delivered to the job site pressurized and with pressure taps, the installation contractor could easily confirm that there were no tubing leaks.

 

Climate Mat was installed in sections composed of six circuits. Each section contained 2,600 linear feet of ½" diameter tubing. Spacer strips were used to maintain a fixed spacing of the tubing per design. To hold the mat in place during the concrete pour, stakes were used in the spacer strips at two foot intervals. Section terminations were heat-fused into floor-recessed manifolds. (Since completion of the HE.5, Climate Mat is now provided as a design-build solution with wall-mounted manifolds.  Sections are available in 6' widths, up to 190 feet in length, with tubing in 6" or 9" on-center spacing.) 

Labor savings in using the Climate Mat versus traditional methods were on the order of 118 man hours per 10,000 ft2 of floor area. Further time and labor savings were experienced in the commissioning of the system, because balancing requirements were minimized due to Climate Mat’s fixed spacing and uniform section lengths. Overall, the radiant cooling system with Climate Mat saved approximately 60-75% in first costs versus a traditional radiant system.

 

Radiant cooling system operation

 

Building energy simulations concluded that pre-cooling the slab during off-peak hours would maximize energy savings, resulting in 50% less electricity than an air-only system, while maintaining comfort and avoiding slab condensation. These electricity savings do not include savings from using pumps versus fans. Because transferring heat with water is a much more efficient process than moving heat with air, the energy savings with the radiant cooling system are expected to be even greater once pump and fan energy are considered.

 

Operational data collected by NREL show that “the radiant floor is performing better than expected.” Monitored slab surface and supply and return temperatures have indicated that there is further potential for radiant system energy savings through reduced flow rates and/or increased supply temperatures. 

 

With intelligent design, radiant cooling can be specified across many climate zones. However, radiant cooling excels in hot dry climates, especially for applications that have large cooling loads and hard flooring surfaces. Areas that have high electricity/tou rates and peak power pricing provide favorable economics for faster paybacks and operational savings. If looking for extra leed points, or specifying a radiant cooling or heating system, ask for Climate Mat to deliver an on-time solution at reduced first costs.