There are usually better ways to heat small spaces than light bulbs. When we moved into our present home, the water pump was installed in the crawl space under the house. I must have cleared 200 used lightbulbs out of there - the former owners used them to keep the pump from freezing in winter. We built an insulated box around the pump and put in a small electric heater. We've had to turn it on once in 11 years.