High Performing Buildings - Spring 2008 - (Page 57) Radiant Heat A commercial size radiant heating system serves a 26,190 ft2 shop and 15,318 ft2 two-story office. Approximately nine miles of in-slab PEX tubing and 16 manifold headers serve 146 loops with 80 radiant zones. During installation, 18 slab sensors were embedded in the concrete throughout the building. The loop service areas are divided into RTU-1 variable air volume (VAV) hotwater-coils, radiant-first-floor, radiantsecond-floor and shop-radiant areas. Generally, the boiler plant operates in full condensing mode with maximum efficiency. The majority of the time the water in the radiant flooring is 80°F. During the coldest winter days, the highest temperature in the radiant loop is 100°F. Because human body temperature is 98°F, visitors to the building often are surprised that the floor seems cool to the touch. Visitors are satisfied after placing one hand through the garage bay doors on the exterior parking surface and the other on the radiant heated slab. The visualization of the embedded sensors and thermal imaging from the infrared camera also intrigues visitors. In the boiler room, a 14,000 Btu/h gas-fired, low nitrogen-oxide, fullmodulation condensing boiler serves four main loops. The hot water loops are provided with variable speed and temperature controls. Loop service is divided into VAV hot-water-coil and radiant-first-floor, radiant-second-floor, and shop-radiant areas. The room also includes a wallmounted, foldout workstation with network connections and the main control panels for the DDC system. Provisions have been made for future connections to a ground-mounted solar thermal heating plant. The standing seam metal roof of 31 Tannery holds 1,276 solar photovoltaic panels. Rooftop Units High-efficiency U.S. Environmental Protection Agency (EPA) ENERGY STAR® HVAC systems heat, cool and ventilate the building. RTU-1 serves the office wing, RTU-2 serves the shop offices, and MUA-1 serves the main shop. The two rooftop units Spring 2008 are equipped with factory-installed controllers. RTU-1 is a 50 ton VAV system with premium efficiency motors, enthalpy economizer, and embedded network controls that serve the two-story office area. RTU-2 is a 7.5 ton constant volume system for the shop office PERFORMING BUILDINGS 57 HIGH
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