I'm a bit confused Could somebody explain to me how i should use my fans in my newly planned grow box. I'm working on using a large fridge freezer, with enviro's and possibly a few cfl's ( depending on the advice i get from another post in lighting). I'm going to get myself a ruck fan ( possibly ) with a filter to extract the warm air, with passive intacts at the bottom. The fridge is going to be stored in a garage which is fairly warm in the summer but not hot, but gets coldish in the winter.

Heres the newbee bit, do i use my fan purely to keep the temperature at a good level, i.e have it connected to a thermostat and it comes on when things get a bit hot. That way the air is only changed whenthings are heating up. Or do I have the fan timed so that it changes the air in the box at regular intervals so my baby will always have nice fresh air to breathe? Or do I do both? Or something totally different?

please could someone explain to a novice a good way to run my ventillation.

Many thanks

The ventilation should always be running 24/7 to take away stale air and excess humidity and to give your plants fresh air to breathe - you can have your fans on a speed controller, and run them at a lower rate during the dark period, for an example of a possible environment tweak, but they should never be completely off, no.

wow scribble, are you my personal guru or what? I cant believe how quickly you reply, thanks loads. Heres another one to keep you going . What happens if things get too cool then and my fan is sucking in loads of cold air over the winter and my lights are n't keeping it warm. do I add a heater to the box or something. Ooops got to log off mrs ippon sounds angry...

I reckon on a heater - may not want it in the fridge cos it will take up too much room - so maybe a thermostatically controlled greenhouse type electric fan heater outside the fridge with the fan blowing in the general direction of the passive intakes - I'm trying that for my growcupboard which is in my shed this winter - or if you do want it inside the fridge maybe a low wattage tube heater type thing. (Garden Centres or B+Q stock fan heaters, ebay search for 'tube heater')

cheers satanic again. will look into those tube heaters as I want to try and keep as much stuff inside the fridge to make it as stealth as poss.