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Mini Split for a Greenhouse or Grow Room
A sealed grow room is a box of hot lights and wet leaves. In Central Texas that box will not stay in range unless you pull heat and moisture out without dumping the air you already conditioned.
You keep the room sealed on purpose. Temperature, humidity, carbon dioxide, and pests stay on your terms. A cracked window or a noisy exhaust fan throws away that air and invites the outdoor climate back in. In a true grow room or a tight greenhouse, heat from the fixtures and water from the leaves have to leave through equipment, not through a hole in the wall.
Grow lights dump heat at the canopy and up at the ceiling, even after dark. Leaves transpire all day. Irrigation, wet media, and damp floors add still more vapor. Outside along the I-35 corridor the summer air is already well over 100 degrees, and past 110 degrees on a bad afternoon. A greenhouse adds solar gain through the glazing. An indoor room adds attic heat and thin walls. The closed box has to reject both loads.
A ductless mini split puts a coil in the plant space and a condenser outside. Refrigerant in a small line set carries heat out. While the indoor coil runs cold, moisture condenses and leaves through a drain. The crew hangs wall units and ceiling cassettes for this kind of room from Waco through Austin to New Braunfels. This page is about light heat, transpiration, and that install, not a living room and not a garage gym.
The Price on the Card
That is materials and labor for a standard single zone mini split installation. One day every week is the Joker Day at $2,200. Which day it lands on changes week to week, and the current Joker Day is revealed on the home page.
A $400 materials deposit books the date. The balance is due on completion.
Call the crew: (512) 297-7493Light heat in a closed room
Every fixture turns electrical power into heat at the lamp and at the driver. That heat sits under the canopy and stratifies near the ceiling. In a sealed grow room you cannot exhaust your way out of it without losing the closed environment you built. A mini split absorbs heat at the indoor coil and rejects it at the outdoor unit. The room air stays in the room.
A greenhouse stacks solar gain on top of the light load. An indoor room stacks wall heat and attic heat. Either way the condenser sits in Texas sun and needs room to breathe. We look for a pad or a wall bracket, airflow around the fins, and whatever shade the site already has. Capacity starts as a general rule of thumb from room volume and a rough read of the fixtures. A site visit confirms that rule. Nothing on this page is a promised size.
- Lights add heat even when the sun is down
- A sealed room cannot dump that heat by cracking a vent
Transpiration loads the same air
Plants move water from the root zone into the air. A full canopy is a humidifier that never clocks out. Trays, wet floors, and hand watering add more. That vapor raises humidity and makes the same air heavier while it also changes how the cooling coil behaves.
When the mini split runs in cooling and the coil surface is below the dew point, moisture condenses and drips to the drain pan. That is how the system dries the room: as a side effect of cooling, not as a separate promise. If the unit short cycles, or if you hold the setpoint so high the coil never gets wet, humidity stays. We talk through plant density and irrigation on site so the machine is not asked to do a job it cannot do.
Temperature and humidity are one fight
In a small sealed box you do not get to treat heat and moisture as two separate problems. Cooler air holds less water. Drive the room too cold to dry it and plants suffer. Hold it warm and the coil may not wring out enough vapor. A mini split gives you a wall control and a setpoint growers already live with, often between 70 and 80 degrees, and it dries while it cools.
Airflow matters as much as capacity. The indoor head has to throw air across the space without blasting one bench and leaving a dead corner. We look at bench layout, hanging height, and whether a wall unit or a ceiling cassette makes more sense. Condensate has to leave through a real drain, not a bucket. Gravity is simplest when the head sits high enough. A pump is the fallback when it does not.
Greenhouse glass and indoor rooms
Glass, poly, and polycarbonate collect sun. That solar load shows up on top of whatever fixtures you hang. An indoor grow in a spare room or a shed does not get that direct hit, but it still takes heat from lights, walls, and a hot roof. Both can be sealed. Both need cooling that does not require dumping air.
Placement changes with the structure. In a greenhouse we watch drip, hanging height, and how air moves down the rows. In a framed room we watch the attic, the door, and a wall that can take the head without sitting on a bench. The outdoor unit still needs clearance in Central Texas heat either way.
What we check before we hang a head
We measure the room, note how tight it is, and look at glazing or skylights. We ask what is hanging: how many lights, what kind, and how long they run. We look at plant load in a plain way, not as a lab reading. We trace a line set path that does not wreck the seal, and we find a home for the outdoor unit that can breathe.
Electrical at the condenser, a drain route that will not flood the floor, and indoor placement that treats the whole canopy are the rest of the visit. Square footage on the phone is only a start. Lights, plants, and sun change the load. The rule of thumb gets confirmed when someone is standing in the room.
Questions People Ask
Can a mini split cool a grow room that stays sealed?
That is a main reason to use one. Heat leaves through the refrigerant lines instead of through exhausted air. The room can stay closed. You still need a condensate drain and a tight hole for the line set. Load from lights and plants still has to match the equipment, which a site visit confirms.
Will the mini split handle humidity from the plants?
While it is cooling and the coil is cold enough, water condenses and drains away. That helps with transpiration load. It does not mean one indoor head replaces every other drying method in a packed room with heavy irrigation. How hard the unit runs, plant density, and setpoint all matter. We look at those together on site.
Where does the condensate go in a grow room?
It runs from the indoor coil to a drain line. You want that line to a real drain so the pan does not overflow onto the floor or into a tray. If the head is high, gravity can do the work. If the drain is uphill, a condensate pump is the usual fix. We plan the route with the rest of the layout.
Can it heat when the lights are off?
A heat pump mini split can reverse and add heat. Some rooms need that on winter nights or when the structure loses heat after lights out. Along I-35 the summer cooling load is still the one that usually drives the choice. We walk through both heating and cooling when we see how the space is built.
I already know the square footage. Do you still need to see the room?
Square footage is a starting point, not a size. Lights, a full canopy, greenhouse glass, and how sealed the envelope is all change the load. Placement of the indoor head and the outdoor unit matters too. A general rule of thumb gets confirmed on site. That is the only way to match the machine to the room.
Book the Job
If your greenhouse or sealed grow room is losing the fight with light heat and wet air, call or text the number on this page. Tell us about the space, the lights, and how you run the room. We will set a time to walk it and talk through a mini split that fits.
Call or text the crew at (512) 297-7493. Tell us the room, the size and whether it is insulated, and send a photo of the wall you want the head unit on. Standard days are $2,400, materials and labor. The weekly Joker Day is $2,200, and the home page shows which day it is this week. A $400 materials deposit holds the date and the balance is due when the job is finished.
Call (512) 297-7493