In our previous article about marijuana grow-room air conditioning, we recommended that you consult licensed professionals instead of attempting amateur installation or a retrofit of your building’s air conditioning system. We also noted the unreliability of generic marijuana grow-room air conditioning formulas that cannabis growers share among each other.
Let’s continue our close look at fundamental marijuana grow-room cooling issues.
First, you need air conditioning capacity that can easily keep your marijuana grow room at target temperature — even if the mercury outside hits 100°F or higher. The marijuana grow room ideal target temperature is variable, depending on the strains you’re growing, whether you add CO2 to your grow op air, what growth phase you’re in, vapor pressure deficit, and a host of other factors.
In general, you need air conditioning capacity that can keep your marijuana grow room at a temperature of 74–81°F, no matter how hot and humid it is outdoors.
Your air conditioning equipment choices are: a room air conditioner (window shaker), a split-unit room air conditioner, a whole-house air conditioner, or a combination of some or all of these types of hardware.
I don’t recommend portable room air conditioners. They’re inefficient at converting electricity to cooling power, cost a lot to run, they add heat to the grow room, lack adequate cooling capacity, and they can be tricky to set up and run.
Most of us grow marijuana in one room of a multi-room domicile cooled by a whole-house air conditioner. Problem is, when you add even one 1000-watt high-intensity discharge (HID) grow op to a home, your existing whole-house air conditioner isn’t likely to easily handle the extra heat, unless the unit was oversized to begin with.
The best strategy is to calculate grow-room heat and other air conditioning needs, and install the system that meets your needs before you put plants into your grow space.
If you have an air conditioning system that lacks the capacity to cool your marijuana grow room, your AC is likely to run constantly when your grow lights are on. Your electricity bill will be sky high, and your AC unit will fail sooner. If your air conditioner is maxed out too much (and especially if it’s older equipment), it could fail completely during a crop cycle — with disastrous consequences.
If you install a new whole-house air conditioner with capacity to cool a one-to-four-light indoor marijuana grow room, make sure you factor in the cost of new whole-house air conditioning, including customized new ductwork, feeds, outdoor unit, coolant, air handler and returns. That could equate to a cost of between $5500–$9000 if you use a professional installer and quality equipment.
The variables affecting the cost of installing a new whole-house air conditioning system include the size of the house, the quality of equipment you install, the number of grow-room lights, and local climate conditions.
If you install a new wall-mounted mini-split unit with 36,000 British thermal units, or BTUs, of cooling power (this unit can easily cool a grow room with up to 3000 watts of lighting), your cost will be significantly less — about $3400, including installation.
If you install a 10,000-BTU window-shaker air conditioner, the total cost of the unit and the install drops to about $1000. Window air conditioners are only strong enough to cool a room that has 1400 watts or less of grow-light capacity. The simple fact is, most window shakers are noisy, energy inefficient, and incapable of adequately cooling a marijuana grow room.
In our next articles, we give you a list of the most reliable brands of air conditioning equipment, and discuss what you should say to licensed air conditioning and electrical personnel so as to preserve your security.