11. Zone controls shall automatically maintain a minimum 5F deadband between space cooling and heating setpoints. That is, if a space is set to 75F cooling and 70F heating and the occupant increases the heating setpoint to 72F, the cooling setpoint shall automatically be increased to 77F. 12. Where a single zone comprises multiple spaces, the spaces shall have similar loads and the same solar orientation. Do not combine, for example, north and east facing perimeter offices on the same zone. It is recommended that all individual offices and meeting/conference rooms are provided with individual VAV boxes and temperature sensors. Where this is not possible, and spaces are served by a common device (e.g., VAV box or FCU) provide variable airflow supply diffusers and individual temperature sensors in each space to allow a degree of individual temperature control. In this case the VAV box will be designed to maintain static pressure upstream of the variable airflow grilles. 13. Implement Demand Controlled Ventilation (DCV) for the space through the use of CO2 sensors or Indoor Air Quality (IEQ) sensors in densely occupied areas 250 square feet or larger, including meeting rooms. Sensors must be between 3 and 6 feet above the floor in open office areas. An IEQ sensor shall be provided in the RA duct to each AHU and be located away from mixed air/outside air intake. Specify a DCV sequence of operation at the zone level consistent with ASHRAE Guideline 36. The zone sensor in densely occupied spaces will increase VAV airflow and the zone sensors together the return air sensor will modulate the AHU OA flow between DCV minimum and design. DCV is recommended but not required for systems equipped with ERVs. 14. Consider installing an air purification system (such as AtmosAir) to reduce gas phase contaminants and biological contaminants in the air. If installing electronic air cleaning systems, ozone levels shall also be monitored in the space. Systems shall be listed to UL 2998 and UL 867. 15. Consider installing an IEQ sensors instead of CO2 or combination CO2, Humidity and Temperature Sensors, to measure and track the following parameters: CO2, PM2.5, TVOC, temperature, and relative humidity. 16. Ductwork design shall be streamlined. Plenum connections should have a minimum 4” 45 degree bevel /chamfer and 6” when transitioning to duct velocities greater than 1200 FPM . Plenum velocities shall not exceed 600 FPM. Bullheaded tees with boot taps on main branches shall not be used above 700 FPM in low pressure ductwork and are forbidden on medium pressure ductwork. The index medium pressure run shall not pass through any boot taps above 800 FPM. Boot taps for branches shall not be used above 1100 FPM main velocity. Mitered elbows with turning vanes shall not be used above 1400 FPM. To avoid system effects, mitered elbows with turning vanes or radiused elbows with splitter vanes shall be used when other fittings are within 5 diameters/characteristic dimensions downstream of an elbow. Higher duct velocities up to 2000 FPM are possible without impacting static pressure by using duct splits and radiused elbows with splitter vanes instead of boot taps.
17. Specify CFC and HCFC-free and low GWP refrigerants.
18. Install energy recovery ventilators (ERV) on ventilation systems to preheat and cool the outdoor air. Consider providing one ERV to serve 2 or more air handling units. Energy recovery systems shall be selected to meet minimum effectiveness requirements of energy code and so as to not impose a fan energy penalty under the fan system power limitations of ASHRAE 90.1-2016 as modified by the 2020 NYCECC or successor codes. ERVs shall be added for all projects where AHUs are replaced or relocated and wherever possible to replace outdoor air fans when AHUs are to be retained.
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