Heaty room

We are growing in an enclosed room under a single 1000-watt HID lamp. We are struggling to keep the temperature under 90 degrees with fans going continually and an open door during lighted hours. We have an air conditioner in the room but after 30 minutes it just spews out hot air. We’ve read that cooling the roots may be the answer to our problem. What do you suggest we do? Will the plants survive in 90-degree conditions?

High temperatures will not kill the plants as long as the roots are kept moist. However, it will ruin the flowers, which will be loose and sparse along a stretched stem. Therefore it is essential to keep the room between 70-76?F (21-24?C) with unenriched air, although you can go up to 82?F (27?C) when enriching with CO2.

An easy way to eliminate the heat would be to stop it from getting in the room. An air-cooled light vents most of the hot air created by the bulb. This air never enters the room. It is drawn from outside through a tube, is heated in the reflector and removed through a second tube. It has no conspicuous odor and can be freely vented.

A single 1000-watt lamp creates about 3200 BTUs of heat. A room air conditioner such as the kind that goes into a window could be used to move the heat into another space such as a room or hallway. From there, the heat could be vented out of the house. If that is inconvenient, you could add another air conditioner. Small portable models can be rolled into the space when needed and vent heat out through a 4-inch tube.

Changing the light cycle so the lights are on at night and off during the day could be a solution. Depending on the area and season, nighttime temperatures may be much cooler than daytime temperatures. Cool outside air could be vented into the space and hot air removed.

Cooling the roots using an aquarium chiller is also a solution. However, there is a learning curve involved. There are any number of reports about cooling or heating roots to counteract above-ground temperatures. If the canopy temperature were 85?F (29?C) degrees, the roots would need to be cooled to 65?F (18?C) to counteract the hot air. It’s probably easier to use an air-cooled reflector and air conditioner.

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