Us DIYers save a bundle by using metal tubing with elbows. Install the fans while assembling, seal for air leaks & install during the building of the room. My 4 x 3 meter flowering room has two of these assemblies. Running during lights on with 2k watts burning, they keep it under 80 degrees, regardless of the outside air temp.
Here's photos to illustrate. 1st is outtake which vents @ bottom outside the room. 2nd is intake which brings in fresh air & distributes it from inside bottom of room. Works great & I have about $40.00 invested in 2 fans, galvanized tubing & elbows. Plus a little labor.
Another DIYers tip. The outtake exhaust is fitted with a tupperware piece that just fits into the galvanized elbow. I poked it full of holes, filled it with $3.00 worth of aquarium charcoal, slapped the lid on, shoved it into the elbow & sealed any air leaks with expanding foam insulation. This works as well as any $100 or more air filter! Way better, since it cost less than $10.00! It's super easy to refill for only $3.00 when it has run its course, too. Just these two tips I believe have saved me several hundred dollars. And the results are equal to or superior to any setup @ any price! I have lots more of these & have been adding them to strings where they seem appropriate.
If everyone used these money savers instead of always having to invest tons of $$$$$ for every rip-off, over hyped, gadget that these unscrupulous companies insist on marketing, I believe we would all save money on the end result! Instead of Farmer A having to charge a ridiculous $400.00 a zip, he could charge $250.00. But he has to recoup his investment, since he overpaid so dearly for everything he used to produce it, from nutes to lights to ventilation system & filters!
Then we can all spend the extra money on the ONLY thing that there is no DIY alternative for & that is genetics. @ the end of the day, it's the most important factor in harvesting a high quality crop, anyway!