Heater for fermentation chamber

I have a temperature controller running a 7.1 cu ft freezer, the freezer alone has been holding the temp down to 65 almost perfectly for the last few months. As we move into winter, I’m expecting the ambient temp in that basement to get to 60 or lower, and so it’s time to add some heating. I’ve also got some Belgians coming which I will want in the mid 70s.

I just put in one of those little ceramic space heaters, but in just 2 minutes it overshoots the target temp by 4-5 degrees. 1500 Watts is obviously overkill, but since I had it on hand, nothing lost. I’m thinking I need to get a more appropriately sized device.

So I’m taking a poll, for those who heat fermentation chambers, what kind of heater are you using and what kind of Wattage is it? I should note that I’m measuring the air temp within the fermenter, not the actual beer temp; that upgrade is down the road a ways.

I’ve got a 1.2 m3 (about 30 cu-ft) fermentation chamber built of 4" thick Styrofoam slabs set up in my outside shed. The heater can put out about 150W max, but I have no problems maintaining temperature even when it is -20C outside. I’d guess a low wattage light bulb would be plenty for your purposes.

I’m using a 60W light bulb in a paint can for roughly the same size freezer. I came across the build instructions on one of the other forums, and it works great.