You just had to say it! I have already elevated my seedlings toward the light using plastic glasses! So what I am gonna do is set the fan with the light timer, so the seedlings will get air circulation during the day. I also could not stand the sound of the fan while I am sleeping, and definitely my sleep is more important than my seedlings ahah! That means the fan will be turned off during the night no matter what. Thanks!

Look at this switch from EFI. Turn the switch ON, it will turn the light and fan on. Turn the switch OFF, the light will turn off but the fan will run for a set amount of time, you set the "DELAY" so the fan can run for up to 60 minutes after the switch is turned off. If you don't want the fan to run for it's timed DELAY cycle, then cycle the switch ON then OFF and the light and fan will turn off. It also has a "VENTILATION" function that you may or may not want to use. That function turns the fan on for a set amount of time per hour. You can set it to zero. EFI also offers this switch, which is slightly different than the one above in that it doesn't have the VENTILATION function. I prefer the first switch, though I almost always have the VENTILATION function set to zero. EDIT to fix link This post was edited by mongoct on Sat, Feb 16, 13 at 0:08

In my current house, sometimes, the lights were turned off automatically at 60 minutes when my daughter was still taking shower. She had to come out of the tub and turned on the lights. Since in my current house, the lights and fan are controlled by the same switch, there is no concern for the ventilation. But for the newly bought house, if I have timer for fan and switch for lights, the light will not be automatically turned off when the fan reaches its maximum 60 min time. I can urge her to finish taking shower within 60 minutes, but I cannot guarantee if she would do it if I am not home.

Here is the simplest scenario to install; two switches on the wall, one turns on the lights the other turns on the fan. You can put a dimmer on the lights, but adjust the fan speed with the pull chain. Anyone with a little experience can wire this setup. If you really want to adjust the fan speed from the wall, that complicates things and you will have to get a specific speed control from the manufacturer or someone with enough experience to be able to give you the one that will work with your fan. In my experience, fan speed controls caused buzzing which annoyed me. I have been happy with the setup described above. Mark F