I've tried wrapping the light bulb in aluminum foil. I quickly ended up with a burnt out light bulb and lamp wiring. Maybe it can be done with a very low wattage bulb. I'm not trying it again though.
When I ran into the problem of needing heat last year, I dug out my trusty reptile heating stone. It's basically a fake rock with a heating element embedded in it to give pet snakes and lizards someplace warm to sit. It emits no light and doesn't get too hot.
I just today bought a single stage Ranco controller. You no longer have to flip a dip switch, the heating and cooling choice is in the menu. That with a fermwrap and I can now ferment in the winter. All on the coldest day of the year here in the bay area. There was snow on mount diablo in the distance as I left the More Beer parking lot.
