Light Deprivation Greenhouses: How They Work and What They Cost

A light deprivation greenhouse — "light dep" for short — is a greenhouse that can be made completely dark on schedule. By controlling exactly how many hours of light the plants get, growers control flowering time. That means multiple harvests per year and harvests timed to market demand instead of the calendar.

How the system works

The core of a light dep greenhouse is the blackout curtain: a heavy, light-proof fabric that covers the entire house — roof and walls. On schedule, the curtain closes and the house goes dark; later it opens and the plants get daylight again.

There are two ways to move the curtain:

Manual systems use a chain crank and roll bar. Lower cost, more daily labor. A good fit for smaller houses or growers watching the budget.

Automated systems use electric roll-up motors with digital timers and controllers. Set the schedule once and the system runs itself. Better for larger houses and anyone running multiple cycles per year.

Either way, the house still needs to breathe. A sealed dark house gets hot fast, so ventilation is critical: exhaust fans, roll-up sidewalls for the daylight hours, and evaporative cooling in hot climates. Light traps on the vents let air in while keeping light out.

What goes into the cost

Four things drive the price of a light dep greenhouse:

1. Size. A 30x100 foot house costs more than a 30x70 — more steel, more fabric, more film.
2. Manual vs. automated. Motors, timers, and controllers add cost but save daily labor.
3. Frame duty. Heavy-duty oval hoops cost more than standard frames and stand up to more wind and snow.
4. Covering. Standard 6 mil greenhouse plastic vs. upgrades like polycarbonate end walls.

The blackout system itself — fabric, motors or cranks, controllers — is the premium over a regular greenhouse kit. When you compare quotes, make sure you are comparing the same thing: frame size, automation level, and whether ventilation equipment is included.

What to watch for

Buy a frame built for the job. Blackout fabric adds weight and wind load, so a flimsy frame is a false economy. Make sure the curtain seals fully — even small light leaks defeat the purpose. And plan your ventilation before you build, not after.

Choosing manual vs. automated

The decision comes down to house size, labor, and how many cycles you run per year.

Manual chain-crank systems cost less up front. The trade-off is daily labor: someone opens and closes the curtain every day, on time, without fail. On a single 30x70 house with a reliable crew, that works fine. On three houses, it gets old fast — and a missed closing ruins a cycle.

Automated systems — electric roll-up motors, digital timers, controllers — cost more but run themselves. The curtain moves at exactly the right minute every day. For larger operations, multiple houses, or anyone running back-to-back cycles, automation pays for itself in labor savings and consistency.

You can also start manual and upgrade later. The frame and curtain are the same; the motors and controllers bolt on when you are ready.

Sizing your light dep house

Width is decided by your crop and equipment — 30 feet is the commercial standard because it fits standard bed layouts and gives working room. Length is decided by volume: 70 and 100 foot houses are the common picks.

Do not undersize. A light dep house at full production holds a lot of plants, and crowding hurts airflow and quality. It is cheaper to build the right size once than to add a second house a year later. If your site allows it, leave room to expand — second houses share the learning curve of the first.

Get a real number

Every operation is different, so we quote by size and system. Call Henry at (630) 408-2201 — tell us the house size you have in mind and whether you want manual or automated, and we will put together factory-direct pricing with delivery on our own truck.