Controlled Environment Horticulture Prescriptive Requirements for Space Conditioning Systems
Measure Overview
This proposed measure would establish prescriptive requirements and revise mandatory requirements for space conditioning systems providing heating, cooling, and dehumidification to support plant growth in Controlled Environment Horticulture (CEH) spaces. These requirements would only apply to CEH facilities with lighting power density (LPD) above a threshold (tentatively 30W/canopy square foot) and a minimum of 5000 sq. ft. of plant canopy. This measure would also provide a performance pathway through updates to California Building Energy Code Compliance (CBECC) software.
The measure would include the development of two or more prescriptive packages based on the plant canopy area. Prescriptive requirements would address mechanical heating, cooling, and dehumidification loads. At least one package would include federally regulated standalone dehumidifiers that are sized, designed, and controlled to be used in combination with efficient cooling, fans, and/or other dehumidification equipment as an efficient system. Prescriptive credit may be allowed for other process and building equipment.
Mandatory requirements would be revised to require the submission of design criteria, assumptions, and sizing calculations for space conditioning systems serving spaces with LPD above 30W/canopy sq. ft. [TBD].
The requirements will likely be the same for all 16 CA Climate Zones. Prescriptive measures would apply to new construction, additions, and major alterations. Replacing a single piece of equipment in a larger system would not trigger the prescriptive requirements (minimum threshold TBD).
As part of the restructuring of the code, this measure would also review and clean up code requirements (such as outdoor air ventilation requirements) that may negatively impact plant growth or efficiency.
Proposal Summary 2 Title 24, Part 6 does not currently include prescriptive measures for CEH spaces, and CBECC does not include a CEH prototype. To provide facility designers with flexibility in equipment selection, CBECC would need to be updated for use in demonstrating compliance using the performance approach
Provide Feedback
This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, submit feedback to [email protected]. Please include the measure name in the subject line.
View the Energy Commission's proceedings and available proposed code language by visiting their CEC 2028 Proceedings Website page.
Scope of Proposed Code Change
| Building Type(s) | Construction Type(s) | Type of Change | Updates to Compliance Software | Third Party Verification |
| Nonresidential | New construction, additions, alterations | Mandatory, prescriptive, performance | Add new feature | No changes to third party verification |
Justification for Proposed Change
CEH facilities, particularly indoor cannabis farms, are among the most energy-intensive buildings in California. In these facilities, the lighting and space conditioning systems make up about 80% of energy consumption, split roughly evenly between them. Each of these two end-uses provides significant opportunities for savings. Until this code cycle, CEH lighting has been the primary focus of Title 24 Part 6, leaving significant opportunity for code to regulate CEH space conditioning systems and achieve deep statewide savings.
Since large-scale indoor farming is relatively new (driven primarily by legalization of cannabis in California), CEH facility designers initially had little choice but to repurpose conventional HVAC equipment and dehumidifiers to manage sensible and latent loads in indoor farms. However, space conditioning systems designed to support plant growth need to adapt to highly variable latent and sensible loads, so sizing, design, and equipment requirements are vastly different from those for spaces designed primarily for 3 human occupancy. Since most conventional fixed-capacity HVAC equipment is designed for steady-state applications, it is poorly suited to the highly variable internal latent and sensible loads that characterize indoor farms.
Over the past decade there have been significant advances in the development of variable capacity, fully integrated space conditioning systems that can quickly adjust to these variations, offering better environmental control and far more efficient operation than fixed-capacity, decoupled systems without integrated controls. Unfortunately, many designers continue to use inefficient fully decoupled equipment in the design of new facilities, even though much more efficient, better performing, integrated equipment is now available from multiple manufacturers.
The failure of the market to naturally adopt this more efficient space conditioning equipment presents an excellent opportunity for the energy code to develop new efficiency requirements for CEH facilities.
The opportunity for energy savings is very high because energy intensity of indoor farms is very high, market adoption of efficient space conditioning systems is still low, and the current energy code language does not address CEH HVAC systems or the interaction between HVAC and dehumidification systems. Statewide CASE Team energy modeling of HVAC and dehumidification systems indicate that energy used by more efficient integrated HVAC/dehumidification (HVAC/D) systems is approximately 40% less than energy use by a decoupled, code-minimum HVAC and dehumidification system. In Smith et al1 , an integrated HVAC/D in Portland, Oregon was shown to save 44% energy when compared to the previously installed code minimum baseline system of packaged roof top units (RTUs) and low cost, stand-alone dehumidifiers.
Relevant Documents
Round One Utility-Sponsored Stakeholder Meeting Materials
-
Use the form above to provide feedback on this measure.
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.