Spa treatment for hotel HVAC system


In January 2009, construction began on a new, upscale Renaissance Boston Hotel & Spa at Patriot Place in Boston. The building’s owner wanted a top performing, energy efficient HVAC system that had the capability to adjust airflow based on demand and would operate more quietly than traditional systems. Typical bathroom exhaust systems use oversized rooftop fans running 24 hours a day to assist in exhausting air from a common riser that multiple bathroom fans exhaust into. Unfortunately, these fans often run continuously, tend to be loud, use a great deal of energy, and exhaust excessive amounts of the conditioned air from the building.

The main challenge of this project was to design a cost-effective fan and control system that could reduce energy consumption and provide a variable exhaust flow based on the number of bathroom exhaust fans that were in use while still properly ventilating the guest bathrooms. The owner of the Renaissance turned to Buckley Associates, which proposed the Greenheck GreenVent system with Vari-Green motor to the design team at Zade Associates, over the traditional fan with a VFD and pressure sensing system.


The Greenheck GreenVent system is designed to maintain a constant pressure setpoint in an exhaust riser, which allows the exhaust airflow to closely match that of the bathroom exhaust fans. This significantly reduces unnecessary tempered air from being exhausted. The GreenVent system includes:

  • 23 centrifugal roof exhaust fans, model CUE-121-VG, with Vari-Green motor
  • 23 GreenVent constant pressure control systems (which include all necessary components for proper system operation).

A GreenVent system was installed in each of the exhaust risers to provide a demand controlled ventilation system. When bathroom fans are not on, less conditioned air is exhausted, providing additional energy and money savings. The GreenVent system monitors the pressure in the duct work and adjusts fan speed from 300 to 1,750 rpm to compensate for the number of hotel bathrooms in use. All fans are direct drive and powered by Greenheck’s high-efficiency Vari-Green motors. The motors are brushless dc (electronically commutated) high-efficiency motors that run off a 115v single-phase input that run quieter and cooler, and offer higher efficiencies with improved speed control capabilities as compared to standard motors. Vari-Green motors are capable of operating from 20% to 100% (80% turndown) of full speed versus 70% to 100% (30% turndown) for PSC motors, which are commonly used on direct drive fans. Although the GreenVent system is typically packaged as one unit, in this case, individual components were delivered to the job site as needed to meet the contractor’s work schedule.

The hotel opened in June 2009, and the system has been a tremendous success, according to Mark Jeffery, general manager of the Renaissance. “Because the fans run at a minimum speed most of the time, they operate more efficiently and are much quieter than our other systems.” The installing contractor, PH Mechanical Corp., Boston, was pleased as well, noting that the system’s clear instructions made the installation process straightforward.

Information provided by Greenheck

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