Hi, I am trying to work out how to apply Addendum ah for ASHRAE 2010 for system 5-8
"G3.1.3.18 Dehumidification (Systems 3 through 8). 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. When the baseline building design HVAC system does not comply with any of the exceptions in Section 6.5.2.3, then only 25% of the system reheat energy shall be included in the baseline building performance. The reheat type shall be the same as the system heating type."
I am not sure if
a) Each project needs to review whether the baseline calculated flow is always <50% design flow when any reheat occurs at the unit or in any spaces. If it is then exception 1 can be applied.
b) This is only when reheat occurs at the system level (not at the room level) as this is classed as "same airstream" and for system types 3-8 this would be when the air is required to pull it down below 55 and reheat to 55.
"6.5.2.3 Dehumidification. Where humidity controls are provided, such controls shall prevent reheating, mixing of hot and cold airstreams, or other means of simultaneous heating and cooling of the same airstream."
"Exceptions:
1. The system is 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."
I think b) is the only option that makes sense but wanted to see what others have found.
Thanks
Victoria
