Please Help Me Set Up My Extractor fan

I have recently set up a small closet grow room, using a 400w HPS for veg and flowering. The temperature with the light on has been too high for optimal growth (only one small fan in grow room to cool). Consequently I have purchased a 10cm wide extractor fan and a few metres of the silver tubing that it connects to (not sure what this stuff is called ).

Can someone please tell me the best way to set up this fan?

I know that ideally two fans are best, one for extracting hot air, one for pumping in fresh air. However i am hoping i can get away with just the one fan extracting hot air. I was planning to cut a circular hole in the top of my closet and then fit the fan to the outside. I am unsure about how much tubing i should attach to either end of the fan. My light reflector does not have the fitting that directly connectects to the tubing. Should i put the extracting tube as close to the light as possiblibe? Or should i just positon it a few feet from the top of my grow room? Also, how long should the tube be thats blowing the warm air out?

Any help would be greatly appreciated, thanks.

 

Jmac, heat rises, I've never used a conduit pipe on my lights. The main reason is; they're outa my price range:>P

As long as the fan is higher than the light, no prob.

 

Installed the extractor fan today. I decided to only attach tube to the outside of my grow room, so the hot air is not released too close.

I have another question if anyone can help. I read somewhere that when measuring temperature, the thermometer should not be in direct light. Instead they suggested putting cardboard over the thermometer as a shade. Can anyone elaborate on this?

 

TRY TO HANG THE THERMOMETER IN THE MIDDLE OF THE PLANTS, THIS WILL GIVE YOU A READING OF THE TEMP AROUND THE PLANTS