Outdoor Greenhouse Ventilation!

[Think]

I'm growing some Think Different they are only seedling atm! I was wondering about getting a fan in there because the cold frame gets way to hot at times! I was thinking about running a extension lead to it but if I have visitors they will be wondering why so I though about getting this battery desktop fan! would this strong enough to blow air on the plants when it's time ?

This is the fan I have found seems pretty good!

 

[furrything]

it is worth remembering that hot air rises, so if there is an opening at the bottom of the tent large enough for cool air to get in from the ground level, even on a hot day the coolest air will be at ground level.
as the cool air enters the green house it heats up inside, so if there is openings at the top of the tent, the hottest air is what will be extracted. this should give you a transfer of air through the day time.
i havent actually done this myself, but in theory it should work, just make sure you dont damage your green house making a hole in it.
its worth considering and its free.

 

[Muddy]

I agree, a vent should be all you need. If you look at all the commercial cold frames they have some sort of vent or a way of opening the top to allow the hot air to escape.

 

[Mr Piggy]

Plus that little coleman fan would crap out on the first day. You would need to wire the greenhouse. Having been in/grown in greenhouses I disagree that ventilation should always be enough. Most large green houses have fans for ventilation and it can help, but most home/hobby greenhouses aren't big enough to warrant one. How big is your greenhouse?