Page Comparison

.01  Application:

1. Application:
   1. Section 23 84 00 of this Standard is intended to cover special circumstances where the occupancy or a process requires humidification or dehumidification outside of the default indoor design criteria defined in Section 23 00 00. 
   2. Centralized or terminal humidification shall not be provided for ordinary space conditioning purposes.

      1. For reference to designer: Humidification systems have the potential to cause considerable damage to building envelopes and contribute to indoor air quality issues. OPP requires specific documentation and approvals to avoid the mis-application of these systems. The successful implementation of a humidification system requires a firm understanding of the environmental requirements, operational capabilities of the equipment, and coordination with other building systems.

   3. Humidification is only permissible to maintain specific environmental conditions for a special equipment or process. These special purposes shall be identified by the designer during the schematic design phase and are subject to review and approval by OPP.

      1. The designer shall document on the design drawings the required temperature/humidity ranges, operational tolerances, and location of all humidified spaces/equipment.

.02

Allocation

1. Allocation:
   1. To preserve the integrity of building enclosures and avoid indoor condensation, the designer shall prioritize allocating humidified spaces to locations without exterior exposure.

   2. Where exterior exposure in humidified spaces is unavoidable the designer shall perform the following building envelope analysis, which is subject to review and approval by OPP.

      1. Calculate the interior surface temperatures at design winter conditions.

      2. Establish the indoor air dewpoint range according to the required temperature and humidity targets.

      3. Identify the risk of indoor condensation to the occupancy and/or process.

      4. Evaluate the effects of moisture migration through the building envelope materials

   3. Humidified spaces shall be provided with vapor barrier to manage moisture migration between adjacent spaces with different levels of humidification.

.03 System Selection

1. System Selection:

   1. Designer shall calculate humidification and dehumidification loads based on indoor design requirements, climatic conditions, and moisture gain due to internal loads, infiltration, and envelope moisture migration. Calculations shall be submitted to OPP for review and approval.

   2. Humidification:

      1. All humidification loads shall be calculated based on ASHRAE Climatic Design Information for the “99.6% Heating DB” condition.

   3. Dehumidification:

      1. All dehumidification loads shall be calculated based on ASHRAE Climatic Design Information for the “0.4% Dehumidification” condition.

      2. Refer to Table 238400.2 - Dehumidification system selection matrix

.04 Recognized Industry Resources

1. Recognized industry resources:

   1. HVAC Systems and Equipment Handbook (ASHRAE)

      1. Humidifiers

      2. Air-Cooling and Dehumidifying Coils

      3. Desiccant Dehumidification and Pressure-Drying Equipment

      4. Mechanical Dehumidifiers and Related Components

   2. The Dehumidification Handbook – Third Edition (Munters)

   3. Whole Building Design Guide (https://www.wbdg.org/)

      1. Building Envelope Design Guide