Winter lagering in the garage

Been trying to figure out a way to lager beer in Canada in the winter without needing a freezer at this point.

I'm thinking about building a fermentation/lagering chamber. It appears that given other research, I should be able to heat it with a lightbulb on an ebay temp controller.

What I was thinking about is building a wooden box lined with foam. I was thinking about a 2'x2' base, 3' high, lined with 3" foam. Just looking for something big enough to hold one carboy/bucket with a little headroom.

Anyone have any thoughts on this?

To elaborate a little further...

I think I'm going to build it 2'x3' and 3' high.

I will raise the bottom up and put the insulation underneath the bottom side to give a solid wood bottom.

I plan to make 2 frames at 2x3 to use as the base and at the top. I will fill in the insides with a double 5/8" layer of polystyrene foam as well as under the base. The top frame used to hold the shape will be recessed down about 2" into the box so the lid will sit down and seal into the box. Plan to use PL300 to adhere the foam to the ply and itself as well.

Will use an STC-1000 and suspend a 40W lightbulb inside the chamber. Also, plan to have a cup of water inside to place the probe into to help combat temperature swings.

When I get there, I will post some pics of the build.

Since warm air rises and you want to suspend the light, you may want a small computer fan to circulate air in there.

Also, be sure to somehow block the light source from the carboy to avoid skunking.

Never thought about the rising - maybe I will mount a box on the bottom with a keyless fixture for the bulb.

Would mounting a computer fan at the top work just to circulate some air? I think I would run it constantly. Any ideas for getting it off the wall of the box to allow it some room to work?

I'm thinking if I get a machinist buddy to make up a small aluminum box to go over the lightbulb - should reasonably act as a heat sink as well? Any worries of the lightbulb blowing due to the heat inside this "heat sink?"