The room is 4 X 3 feet, with a height of 7 feet. The walls are lined with mylar and the room is lit by a 250 watt HPS lamp with an enclosed ballast. I use a passive hydro system. The space is ventilated using a bathroom exhaust fan a the top of the wall. Cool air is vented in passively through three 1 inch holes at the bottom of the wall. Air is circulated in the garden using a 4 inch circulation fan.
The area of your space is 12 square feet. Right now you are providing an input of about 20 watts per square foot. A 400 watt lamp would give the garden an input of 33 watts and a 600 watt 50 watts. The 600 watt lamp or two 400’s would be more suitable for the garden.
There are several ways to deal with the heat problem. First, the light that you are using creates excess heat because of the enclosed ballast. If the ballast were remote, the heat that it created would be emitted outside the space. Switching to higher wattage lamps with remote ballasts would improve the garden yield considerably.
If you do decide to buy new lights, use air cooled reflectors. These reflectors enclose the heat using a glass plate. The heat is vented to and from the room using a 4 inch width tubing and fans attached to the reflector. The hot air is ?clean? because it was never in the room. It can be used inside the house for heating. This prevents a considerable amount of heat from getting into the room.
Rather than using a bathroom fan, switch over to a squirrel fan (available at indoor garden shops). These fans have considerably more capacity to move air and will vent out the heat much quicker. To improve capacity further, use a second squirrel fan tot vent air into the room instead of the three small holes, which allow very limited air intake.
Air circulation in the room would be further improved using a 12 inch revolving table fan mounted on the wall.
By using remote ballasts, air cooled reflectors and better ventilation, the heat problems in the room should dissipate. However, if the room is still too hot, (above the mid-70’s (over 20?C)), then the next step is to install a portable or room air conditioner. A 1000 watt lamp produces about 3200 btu’s of heat, so a small capacity air conditioner will be suitable.
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