3.7.7.1 General

90.1-2019

Humidifier Type
Applicability	Optional humidifier
Definition	The type of humidifier employed. Choices include: Hot water Steam Electric Evaporative humidification Adiabatic humidification
Units	List (see above)
Input Restrictions	As designed
Baseline Building	For systems serving zones where humidification is included in the proposed design, the baseline shall include the same humidifier type unless the proposed humidifier does not include automatic shutoff valves and insulated dispersion tubes meeting the requirements of 90.1-2019 Section 6.5.2.4. In that case, adiabatic humidification shall be used in the baseline. In either case, the baseline humidification system uses the same schedule and setpoints as the proposed building.

Humidistat Maximum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Building	If the proposed design HVAC system(s) have humidistatic controls, then the baseline building design shall use mechanical cooling for dehumidification and shall have reheat available to avoid overcooling. Systems serving computer rooms shall not have reheat for dehumidification. The reheat type shall be the same as the system heating type. Only 25% of the system reheat energy shall be included in the baseline building performance, when the baseline building doesn’t comply with any of the exceptions listed below (Standard 90.1-2019 Section 6.5.2.3). The requirements and exceptions to the same are listed below- Humidity controls shall prevent reheating, mixing of hot and cold airstreams, or other means of simultaneous heating and cooling of the same airstream. Exceptions : The system is capable of and configured to reduce supply air volume to 50% or less of the design airflow rate or the minimum outdoor air ventilation rate specified in ASHRAE Standard 62.1 or other applicable federal, state, or local code or recognized standard, whichever is larger, before simultaneous heating and cooling takes place. The individual fan cooling unit has a design cooling capacity of 65,000 Btu/h or less and is capable of and configured to unload to 50% capacity before simultaneous heating and cooling takes place. The individual mechanical cooling unit has a design cooling capacity of 40,000 Btu/h or less. An individual mechanical cooling unit is a single system comprising a fan or fans and a cooling coil capable of providing mechanical cooling. Systems serving spaces where specific humidity levels are required to satisfy process needs, such as vivariums; museums; surgical suites; pharmacies; and buildings with refrigerating systems, such as supermarkets, refrigerated warehouses, and ice arenas, and where the building includes site-recovered energy or site-solar energy that provide energy equal to at least 75% of the annual energy for reheating or for providing warm air in mixing systems. This exception does not apply to computer rooms. At least 90% of the annual energy for reheating or for providing warm air in mixing systems is provided from site-recovered energy (including condenser heat) or site-solar energy. Systems where the heat added to the airstream is the result of the use of a desiccant system, and 75% of the heat added by the desiccant system is removed by a heat exchanger, either before or after the desiccant system, with energy recovery.

Humidistat Minimum Setting
Applicability	Systems with humidity control
Definition	The control setpoint for dehumidification
Units	Percent (%)
Input Restrictions	As designed
Baseline Building	Same as proposed