Blue is correct again, and don't worry, you are not being thick, being thick would be not asking questions.
Firstly, it will probably be warmer in your attic so sucking air in will not cool your grow area, as Blue says, suck the air from the top of your grow room into your attic and a few small holes lower down will pull cooler air into the grow room as the warmer air above is sucked out.
Warm air rises so the hottest air you want to dispel will be above your plants with the cool air you want to suck in being lower, and herein lies another issue.
Depending on many variables it could be that the temperature at floor level is too cool to suck in over your plants and could cause issues, I know these oddities from keeping reptiles.
The best bet I would recommend would be a line of holes each about and inch or 25mm in diameter, about 3 inches or 75mm apart running vertically from floor level up to the height of half way up your grow area, you then have an infinitely adjustable way of pulling in cool air by simply covering or uncovering the holes with bits of gaffer tape (duct tape in USA)
Too hot ? uncover more holes nearer the floor.
Too cool ? Cover the lower holes and have a few holes at say, a foot or so off the floor, its all a matter of watching for and recognising signs of stress.
All you need in that instance is a camera and the ability to post photos and you can guarantee someone on here will know what your issue is.
Other than that you are on to a winner with that set up.
Happy growing.
Blue beat me to it but a picture is worth a thousand words.
Nice one Blue.
Cant wait to see those plants bursting to life I use biobizz too love it! Blue id hit you with more Reps but cant 
