Controlled environmental horticulture (CEH) is an agricultural method that utilizes technology to maintain optimal growing conditions under electric light in indoor warehouse and greenhouse crop production facilities. CEH is most commonly practiced in the production of herbs, vegetables, microgreens, flowers, and cannabis. Because CEH facilities must artificially replicate the environmental inputs needed to produce crops (light, water, air, nutrients, the right temperature, and space and time to grow), CEH facilities are energy-intensive operations. Many CEH facilities have separate rooms for each stage of plant development so that inputs and controls can be set to meet the plants’ needs at each stage: seedling, propagation, vegetative, flowering, and ripening. In response to California legalizing adult-use cannabis under the Medicinal and Adult–Use Cannabis Regulation and Safety Act (MAUCRSA, effective January 1, 2018), California has experienced a marked increase in the number of CEH facilities, particularly indoor CEH facilities in urban areas. This surge is forecast to significantly increase the energy demand from the CEH sector (New Frontier Data 2018).
The Statewide CASE Team proposes to categorize CEH operations as a covered process. The proposed submeasures apply to new construction, additions to facilities with CEH operations, alterations that change the occupancy classification of a building (for example, a warehouse converted to a CEH facility), and alterations that involve installing new dehumidification systems in CEH facilities.
Proposed Code Changes
To address this marked increase in energy demand by the CEH sector, the Statewide CASE Team proposes three submeasures related to CEH facilities:
- Horticultural lighting minimum efficacy,
- Efficient dehumidification and reuse of transpired water, and
- Greenhouse envelope standards.
Horticultural Lighting Minimum Efficacy
The horticultural lighting minimum efficacy submeasure proposes a mandatory requirement for minimum photosynthetic photon efficacy (PPE) of 2.1 micromoles per joule (µMol/J) for luminaires used for plant growth and maintenance in indoor growing facilities with more than 1,000 ft2 of canopy and a minimum PPE of 1.7 µMol/J in greenhouses with more than 1,000 ft2 of canopy. The submeasure requires time-switch controls and multilevel lighting controls in both types of CEH facilities.
The submeasure applies to new construction, additions to CEH facilities, alterations that change the occupancy classification of a building (for example, a warehouse converted to a CEH facility), and alterations that involve replacing 10 percent or more of the luminaires serving an enclosed space.
Efficient Dehumidification and Reuse of Transpired Water
The efficient dehumidification and reuse of transpired water submeasure mandates the use of one of the following dehumidification systems in indoor growing facilities:
- Integrated HVAC system with on-site heat recovery for reheating dehumidified air; or
- Chilled water system with on-site heat recovery for reheating dehumidified air; or
- Solid or liquid desiccant dehumidification system.
Facilities with less than 2,000 ft2 of canopy in combined CEH spaces are permitted to use stand-alone dehumidification units with a minimum energy factor of 1.9 liters per kWh (L/kWh).
The submeasure requires the on-site heat recovery system to be designed to fulfill at least 60 percent of the facility’s dehumidification needs during peak dehumidification periods. Furthermore, under this submeasure, dehumidification equipment must have the capability to reuse transpired water for irrigation in indoor growing facilities. This submeasure exempts CEH facilities from the prescriptive requirement to install an air-side economizer when carbon dioxide (CO2) enrichment is used as a strategy to promote plant growth.
The proposed submeasure applies to newly constructed facilities and newly installed HVAC and dehumidification systems in existing facilities.
Greenhouse Envelope Standards
The greenhouse envelope standards submeasure is a code cleanup measure that proposes the following envelope requirements specific to conditioned greenhouses:
- Opaque wall and roof assemblies must meet the existing insulation and building envelope requirements in Section 120.7 and 140.3(a).
- Non-opaque walls assemblies must have a weighted average U-factor of 0.7 or less; and
- Non-opaque roof assemblies must have a weighted average U-factor of 0.5 or less.
The submeasure also exempts greenhouses from existing prescriptive building envelope requirements for window wall ratio, skylight roof ratio, and daylighting requirements for large enclosed spaces. The proposed submeasure applies to newly constructed greenhouses and to greenhouses being converted from unconditioned to conditioned.
Since this submeasure is a code cleanup effort, there are no associated savings or incremental costs.
Submeasures Moved to Future Code Cycles
The Statewide CASE Team is no longer pursuing the proposed changes listed below.
- Environmental and Irrigation Controls
- Circulation Fan Minimum Performance Specifications
Measure proposals, supporting documents, and other outside references will be made public as they become available.
Round Two Utility-Sponsored Stakeholder Meeting Materials
- Presentation – April 16 – Controlled Environment Horticulture
- Controlled Environment Horticulture Submeasure Summary (Updated 4/15/2020)
- Notes – April 16 – Controlled Environment Horticulture
Round One Utility-Sponsored Stakeholder Meeting Materials
Give Us Your Feedback
The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.
Use the form above to provide feedback on this measure.