Setting up a Small Space with 400 Watt Lighting

Hi Scott, I have a space of 70cm (W) x 56 cm (L) x 2.5 m (H) in my bathroom which i intend to use for indoor hydroponic purposes. The top (i.e. the height can be varied easily) as well as one of the sides are open. – What kind of HPS light system would you recommend? – Do you think the space is too small for a a 400W HPS light system? – will it be necessary to enclose the opened top and side? – Will the bathroom humidity be a problem if I have a wall fan? – How about the electricity bill … how much do you estimate it will cost me to operate whatever lightinng you advise? Thank you and kind regards, P.S: Found a lot of answers in your FAQ. Thanks for that!! 
Hello
Lots of Questions.
1. Having one side open is a problem for ventilation. Ideally Fresh Air enters low, where it is cooler and higher in Carbon Dioxide (a heavy gas).  Then it is drawn upwards through the plant foliage and CO2 is absorbed, moisture is transpired from the leaves, and the warmer, moister air will be drawn up into the exhaust fan near the top which is for removing excess heat (which rises) and moisture and Oxygen that the plants produce. A circulation fan might ensure that all leaves are able to access the FRESH air because this is a priority for good healthy growth. Now with one wall open, the air will not tend to rise up through the leaves, but come in through the opening, take the easiest route and go straight OVER the plant and out the exhaust fan. The plant will sit in air that becomes hot and stagnant and the plant will become sick. Enclose the growroom thoroughly with low leakage to ensure the FLOW of air past every leaf. Light and Air is critical, and without sufficient of both, plants will not grow or be healthy.
2. HPS lamps – 400W will do a maximum area of about 1m x 1m and about a 50-70cm plant well. It also will add about 3-5 degrees to your growroom temperature. So we can’t really go any bigger. The issue is that smaller lights generally don’t do a plant tall enough to be worth the effort. So a 400W with good Fans is my recommendation. since 1000Watts is about 12centre per hour, that relates to about 4-5 cents per hour. About the same as 10x40Watt fluros or a waterbed. Check your TV, Stereo, etc. The typical window mounted Air conditioner is about 2400W. The 130Watt fluros (see http://www.hydrocentre.com.au/130Wlites/index.htm) could be used, one at the top and one on the side, reducing heat overall, but still not as fast as a 400W HPS system because the light levels are lower.
Scott Andrew
Nerang Hydroponic Centre 4/50 Spencer Road Nerang  QLD 4211 Australia  Phone (07) 5527 4155 
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