My flower room is about 12 x 8 x 7 with 2 x 1000watts lighting. For venting I have a 10 inch fan pulling air from outside in, and the same size fan with a filter venting into my house. The fans have been running 24/7 since day one (late spring), but I have been noticing a decrease in yield & I wonder is it linked to decreasing temps of autumn/winter.

My lights run at night (7pm-7am) so the room is warm then, but now during lights out Im pulling in colder outside air all day. I realize the temperature difference from high to low will have an effect on yield, but is it ok to have the fans running on the same timer as my lights, and therefore have no intake/outake during lights off?

I have 2 oscillating floor fans on to keep air moving within the room that I would leave on 24/7. I'm located in the pacific north west, so its not freezing temps im pulling in, but it can get cold. I'll get some accurate temp/humidity measurements over the next few days if that would help with any help.

Thanks everyone!

Not to answer your question, but why don't you switch the fans. Like vent the exhaust outside and pull intake air from the rest of the house? It can get pretty cold at night and your bringing that cold air inside a room when ideally you want the temperature to be around 70-75. Plus you don't want to have more than 15 degrees change in the hottest to the coldest temp.

Thanks for the reply, I'm quite cautious about the smell which is why I'm venting into my house. Having said that since the filter is doing a really good job perhaps I should switch, if even just for the winter months.

That said, the heat from the lamps makes the night air quite warm, its the early morning (7am - noon) when the lamps are off and the cold air still coming in that are causing the biggest drop.