Greetings Grow Ninjas

I need to pick you all's brains
My son is moving out in June, and I get one of my back rooms for my tents, given that I can keep the smell confined to that room. I've got a carbon filter in with them right now but even with them in the garage the house tends to smell in the morning. I don't want to have to shell out 3-400 bucks for a scrubber if there is another option on the cheap.

Run to sawage pipe, chimney on roof and keep room at neg pressure pumping out of one of them at all times. If I could do a full room grow for sure what’s the price of dry wall and a bit of paint vs a scrubber that only got a short life span. The reason it smells in the morning is your exhaust fan shuts of to keep temp up, grow tents are not air sealed lol it’s light only to a degree still they leak a tad. The only thing that may help for smell in garage is to run a loop back scrub that’s runs 24/7 or set it up so when your exhaust goes off it goes on to scrub air then go back to tent still there will be some leakage but should notice a huge difference.

I'm moving them into the back room to try to save on electricity. If I vent my extraction fan outside my a/c will run constantly, defeating the purpose of moving it inside. I live basically on the edge of a desert 100°+ is expected in July August and some of September. My girls did ok last summer but I was trying everything to keep their tents cool. My extraction fan with carbon filter runs 24/7, would a hepa filter help in the battle?

Look into the Ona brand smell nuetralizers. I’ve never personally used them but I’ve seen them blasted all over grow sites in positive terms. Might want to do some math as to how long they last and how often you’d need to replace/replenish.