are you planning on crawling into the doghouse and then opening the the door in the house to get to the plants? if so you might want to hang a rug or something over the enterance so when you go in and open the door no light shows up, cause a guy crawling into a doghouse and then a really bright light would look pretty damn suspicious
.. and making a light trap to go ontop to keep the light frow showing up from the exhaust would be pretty easy to make... i'd make a light trap for the air intake aswell. and for a room that size i'd fit asmany 4' or 8' flourecent tubes in there as i could fit... aiming for
atleast a total of 1000w... preferably upwards of 1300.. keep the lights on chains so you can bring them right down on the plants, without gettin them too hot... probably about 6"...
heres a pic of an easy light trap.... you get what im tryin to draw....