you'll need at least a 243cfm to keep that size area at a moderate temp using a 400wt lamp,and a passive filtered vent opening(about 12x12 on lower opposite wall side of the fan)so that there is free air exchange in between the room and lamp....bonbon
bonbon Reviewed by bonbon on . HPS Heat Dynamics For all those experienced with HPS lighting, I would like to know, is there a significant difference in heat output between a 250/270W and a 400/430W HPS light? The room is 6.5 ft. long x 7 ft. tall x 3 ft. wide (approx 137 cubic ft.) Would it be sufficient to install a 4" 148 cfm exhaust fan to control heat or would the light need to be air-cooled? Thanks for all help. Rating: 5