Zonal Hydronic Cooling to Eliminate Reheat
John Weale, P.E., LEED AP®, Integral Group
Reheat is an efficiency scourge that afflicts the typical laboratory. Laboratories typically have a mix of high airflow rooms with widely varying equipment loads that make reheat difficult to avoid with a standard variable air volume reheat system design. In actual operation, the cost of reheat is typically far worse than energy models predict (unless the Labs21 energy modeling guidelines have been carefully followed). During this presentation, the speaker will use case studies and experiences from many years of fighting the reheat problem, while zonal cooling will be investigated as a means to defeat reheat.
One design approach to eliminate reheat is to move the cooling out to the zonal level. When cooling at the zonal level, the ventilation air handler provides air cooled only to neutral (typically 75 degrees Fahrenheit) and heated only to preheat levels (50 degrees Fahrenheit). Each individual zone provides the cooling or heating required by that zone, eliminating the reheat situation where lightly loaded zones are essentially turning on heaters (reheat) while the central system is using energy to provide cold air.
There are several hydronic systems available that can be used to eliminate reheat, including active chilled beams, fan coils, and radiant cooling. Each of these systems has its own pros and cons that the speaker will discuss. The speaker will share lessons learned from implementing these systems, along with the operational and construction budget implications.
John Weale is an engineering fellow at Integral Group. Mr. Weale has been involved as a lead designer or key technical advisor on most of Integral Group's significant projects, including four LEED® Platinum and five LEED Gold buildings (including laboratories). He is proficient in energy modeling and analysis, as well as design, and has extensive experience with highly energy-efficient mechanical systems for critical environments (cleanrooms, laboratories, and data centers), and a wide range of other building types and central plants. In the high-technology sector, Mr. Weale has designed many high-efficiency systems for cleanrooms, laboratory buildings, data centers, and manufacturing buildings with specialized cooling, ventilation, exhaust, and pressurization control requirements. Mr. Weale is a specialist in optimized laboratory fan systems and has served as an instructor for the Labs21 Low Pressure Drop design course.