Rehau recently announced completion of a radiant floor heating and cooling system for a historic warehouse located on Pier One, the northernmost pier on San Francisco’s Embarcadero. What makes the Pier One project a unique is not the use of a radiant floor heating (RFH) system to heat the building, but its use to cool it. In fact, according to industry experts, this is the first documented application of a radiant floor heating and cooling system in North America. Through incentive funding provided by the Port of San Francisco, the pier’s entire climate control system was redesigned for commercial and public use by the expert team of REHAU and the San Francisco engineering firm Flack + Kurtz. The renovated pier opened in December 2000.
The pier and its warehouse were originally constructed in the 1930s for use as a sugar terminal where ships unloaded cargo for storage and distribution to a nearby railroad spur. Recently, however, the pier was being used as a car park and despite its waterfront location, no renovations were planned due to proximity of the Embarcadero Freeway. After the freeway collapsed during the 1989 earthquake, the Port of San Francisco initiated plans to revitalize Pier One by converting it to office space.
The Pier One warehouse presented a unique situation because it was never designed to be heated or cooled. A key challenge, then, was to overcome a lack of insulation in the structure, which has exterior walls of 4-inch solid concrete. Although concrete provides considerable thermal mass, meaning it heats up and cools down slowly; it does not provide an effective means of insulation.
To maintain the historic integrity of the warehouse, funding requirements developed by the California State Historic Preservation Office, in cooperation with the Port of San Francisco, specified that no insulation be installed on the exterior walls. They also wanted a system that would not obstruct the exposed beams and rafters of the building or the “clear story” at the roof peak. According to Flack + Kurtz associate Allan Montpelier, “A radiant floor system minimally impacts the aesthetic quality of the office space while providing optimal comfort and energy efficiency by using the RFH system to both heat and cool the building.”
REHAU was selected based upon their technical knowledge, expertise and proven track record, and was therefore able to provide important problem solving support for the project. rehau’s RAUPEX O2 Barrier cross-linked polyethylene (PEX-a) pipe was selected for its durability, and for its simplicity of installation. The pipe is a proven performer—strong, reliable, lightweight, and flexible. In the Pier One warehouse, nearly132,000 feet of 3/4-inch pipe were installed 10 inches on-center in approximately 250-foot circuit lengths. The circuits were placed on an existing concrete slab over a layer of insulating bubble foil, which helps direct the heat or cold up through the carpeted floor.
The pipe circuits connect to 68 of REHAU’s exclusive PRO-BALANCE™ Manifolds with Gauges, which optimize flow rates and temperature mixing of the system’s heat transfer fluid. Flack + Kurtz preferred REHAU’s manifolds because of their high quality and the gauges allow the operator to easily fine-tune flow rates for each circuit.
The two floors of the finished warehouse provide about 160,000 square feet of office space. Perimeter and interior zones are individually controlled to allow adjustments in areas with different heating requirements. A direct digital control system anticipates building use and activates heating or cooling a few hours in advance; this system saves energy by tempering the concrete thermal mass in accordance with anticipated heating/cooling demands.
In designing the Pier One system, engineers realized that the system could also be used for cooling. When activated, a dedicated chiller cools the heat transfer fluid, lowering the temperature of the thermal mass, which in turn lowers the mean radiant temperature
(MRT) of the building. For the Pier One project, the architects designed an environmentally friendly subsystem that safely cools the hot components of the chiller via a closed-loop circuit of RAUPEX pipe.
A life cycle cost analysis (LCCA) by Flack + Kurtz anticipates energy savings of 15 percent over 10 years for the system compared with a standard HVAC system. Although base building construction costs were higher for the radiant system, tenant improvement costs (the costs to fit out the building shell for tenants) were lower because the system does not require the extensive ductwork of an HVAC system. After installation, the LCCA showed lower operating costs and a lower impact on usable building area.
