High Performing Buildings - Spring 2009 - (Page 16) Modulating condensing boilers with variable loop flow keep return water temperature low and efficiency high. Photo © LHB the enclosed first floor until it warms enough to rise into the commons. ASHRAE Standard 62.1-2001 criteria were used to determine required ventilation rates for each space. The majority of spaces are supplied by 100% air VAV box controllers so most rooms have a traceable method of assuring ventilation rates. Additionally, each AHU system is equipped with airflow measure stations for supply and exhaust/return. Touring groups frequently comment that the air inside is as fresh as that found outside. Thermal Comfort The radiant floor, efficient glazing systems and low-velocity air-distribution system result in thermal comfort that exceeds the industry standard of 80% satisfied. Humidity control is not an issue in this climate due to the low dew points during the school year. Lessons Learned • The combustion air preheat system was • Due to tightening budgets and a failed not installed with a glycol loop. This maxioperating levy, the school has reduced mized efficiency and simplified installation. the operation of the pool as a costHowever, during a pumping system malfuncsavings measure. tion, the coil froze and allowed the heating loop to lose pressure and circulation. • A closer examination of the hours that various parts of the gymnasium unit • The hot water temperature maintenance would be in use may have allowed the system was specified as a mechanical use of a smaller energy recovery unit item, but was installed by an electrical at the expense of additional controls. contractor and had a number of start-up issues that continued for over a year. We • Energy recovery unit bypass ductwork will specify factory commissioning and would have been advantageous for those startup until local contractors become rooms with significant solar heat gain at more familiar with such systems. the expense of more complicated ductwork and controls. At this time conditions • The remotely operated windows failed early sometimes require manual intervention and repairs took some time. Generally, it by operation of the windows, which is not seems that manufacturers produce these a bad thing with the normal airflow in the systems to meet residential demands, rooms and the high exhaust, but is a point not commercial standards. This issue has of discussion for future projects. been noted in the active façade research done by Lawrence Berkeley National • LHB continues to propose design soluLaboratory and requires more robust prodtions using thermal displacement ventilaucts, perhaps from Europe. tion and radiant heating (and cooling) for many of our clients as we believe these • The clerestory windows’ southward orientechnologies can provide a superior intetation assists with natural ventilation, but rior environment at a lower operating cost a northerly orientation would have reduced and at more than fair installation costs. glare. Additional analysis of northerly facing versus southerly facing clerestories should have been performed to understand all aspects of this issue. Innovations To improve the available wall space for classroom cabinets it was desired to provide room heating without the use of fin tube radiation. This suggested the use of radiant floor systems to handle sensible loads. Research by the design team did not find U.S. examples of systems combining radiant floor heating with TDV, but engineering analysis suggested that as long as the floor temperature was kept at less than 80°F, a system combining the two technologies would work as intended. TDV diffuser suppliers were asked to supply either CFD modeling or full-scale testing of a sample classroom to confirm the design team’s design theory. Full-scale physical modeling was conducted by the TDV diffuser supplier to confirm proper 16 HigH Performing Buildings spring 2009
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