I have always used outside air to cool my 1000w, all my fans are outside except the high heat emergency fan which is inside. It gets very cold here in the winter -35 and pulling that air in causes all kinds of condensation issues. It has never cost me a bulb but the water dripping all over is a pain. I use a speedster controler on all my fans now so I can control the amount of air going through the lights and this has cut the condensation down to very little. I always push air so if there is a leak it does not go outside and the fans are not under high heat from the exhaust air. I buy the best flex line I can get but have had 2 failures over the last 8 years, the uv causes the breakdown and they just split. I started using metal flex but am not too crazy about it as it's so stiff. I do have some insulated ducting and it works the best.