My larger space maxes out at 4x5 and is a tent, ventilated and environment controlled. The 2x2 space earlier mentioned is not ventilated. Cold shouldnt be a problem for either. I think the 135 rspec is a great choice for the 2x2. The 4x4/5 would be covered great by one of the larger hlg light, however now that im replacing both these the picketbook comes into play. I was wondering about pissibilities for that space. I already have a third 4x5 with a 1000w hps. This is a legal grow btw, max 12 flowering girls in the 4x4/5s between the two tents and another 3x3 area currently covered my the mars hydro ts2000 with yet the last space being my new setup in the 2x2. Lots of areas! Lol