2025 Controlled Environment Horticulture FAQs

The 2025 Energy Code includes requirements for all newly constructed controlled environment horticulture (CEH) spaces including conditioned greenhouses. Section 100.1 includes the following definitions for CEH space and conditioned greenhouse:

• A CEH space is a building space dedicated to plant production by manipulating indoor environmental conditions, such as through electric lighting, irrigation, mechanical heating, mechanical cooling, or dehumidification. A CEH space does not include building space where plants are grown solely to decorate that space.
• A conditioned greenhouse is provided with wood heating, mechanical heating that has a capacity exceeding 10 British thermal units (Btu)/hr-ft², or mechanical colling that has a capacity exceeding 5 Btu/hr-ft².

Section 120.6(h) includes mandatory requirements for newly constructed CEH spaces that cannot be traded off. CEH spaces must also meet the applicable envelope, mechanical, and lighting requirements for nonresidential buildings. 

The requirements for additions and alterations to CEH spaces are found in Section 141.1(c).

The Energy Code has requirements for indoor growing dehumidification equipment, horticultural lighting, and electrical power distribution systems. For conditioned greenhouses there are also requirements for building envelope and space-conditioning systems.

Indoor Growing, Dehumidification

Section 120.6(h) requires dehumidification equipment to be one of the following type of systems: 

1. Dehumidifiers subject to regulation under federal appliance standards tested in accordance with 10 CFR 430.23(z) and Appendix X or X1 to Subpart B of 10 CFR Part 430 as applicable and complying with 10 CFR 430.32(v)2.
   • Note: Commercial dehumidifiers do not need to be listed in the Department of Energy compliance certification database. Furthermore, the California Energy Commission does not maintain a list for commercial dehumidifiers, and the units do not need to be listed in the California Code of Regulations Title 20 appliance database (MAEDbS) since dehumidifiers are a federally regulated consumer product.
2. An integrated HVAC or chilled water system with on-site heat recovery designed to fulfill at least 75 percent of the annual energy for dehumidification reheat.
3. Solid or liquid desiccant dehumidification system for system designs that require dewpoint of 50°F or less.

Indoor Growing, Electrical Power Distribution System

Electrical power distribution systems serving CEH spaces shall be designed so that a measurement device can monitor the electrical energy usage of aggregate horticultural lighting load.

Conditioned Greenhouses, Building Envelope

Conditioned greenhouses shall meet the following requirements: 

1. Opaque walls and opaque roof assemblies shall meet the requirements of Section 120.7.
2. Nonopaque envelopes shall have two or more glazing separated by either air or gas fill. 

Conditioned Greenhouses, Space-Conditioning Systems

Space-conditioning systems used for plant production shall comply with all applicable requirements in Section 140.4. 

Horticultural Lighting

In a building with CEH spaces or a greenhouse with more than 40 kilowatts (kW) of aggregate horticultural lighting load, the electric lighting systems used for plant growth and plant maintenance shall meet all the following requirements: 

1. The horticultural lighting systems shall have a photosynthetic photon efficacy (PPE) rated in accordance with ANSI/ASABE S640 for wavelengths from 400 to 700 nanometers and shall one of the following:
   • Integrated, nonserviceable luminaires shall have a rated PPE of at least 2.3 micromoles per joule
   • Luminaires with removable or serviceable lamps shall have lamps with a rated PPE of at least 2.3 micromoles per joule.
2. Time-switch lighting controls shall be installed and comply with Section 110.9(b)1, Section 130.4(a)4, and applicable sections of Reference Nonresidential Appendix NA7.6.2.
3. Multilevel lighting controls shall be installed and comply with Section 130.1(b).

The 2025 Energy Code requirements for additions and alterations to CEH spaces are defined in Section 141.1(c) as follows:

Indoor Growing, Space-Conditioning Systems and Dehumidification

• All newly installed heating, ventilation, air-conditioning systems or dehumidification systems in buildings with indoor growing shall meet the applicable requirements of Section 120.6(h)1 and 120.6(h)2. 

Greenhouses, Building Envelope, and Space-Conditioning Systems

• A greenhouse being converted to a conditioned greenhouse or additions to a conditioned greenhouse shall meet the requirements of Section 120.6(h)3 and 120.6(h)4, which are explained above.

Indoor Growing and Greenhouses, Horticultural Lighting

• When alterations to horticultural lighting systems increase lighting wattage or include adding, replacing, or altering 10 percent or more of the horticultural luminaires serving an enclosed space, the newly installed, replaced, or altered lighting shall meet the requirements of Section 120.6(h)5. Any alteration limited to adding lighting controls or replacing lamps, ballasts, or drivers do not need to comply with these requirements.

PPE is is photosynthetic photon flux divided by input electric power in units of micromoles per second per watt, or micromoles per joule as defined by ANSI/ASABE S640. A variety of options exist to determine the PPE of a given product. The Design Lights Consortium (DLC) Qualified Products List notes the PPE level of more than 415 products from popular lighting manufacturers. If the product is not found in this listing, the manufacturer’s product specification may list PPE.