I have a small 36h x 24l x 19w (inches) that I want to put in the unheated garage to start a few seeds. I have the lights setup, but not sure the best (and cheapest) way to provide heat.
Its obviously not a large area to heat and I only need to warm the inside about 10-15 more degrees. I'm thinking a heat lamp bulb in one of those plug in plant lamps would do the trick. I'm extremely hesitant about an electric heater in such a small space, any ideas?
the most common & efficient is a small heating mat similar to the heaters on water beds
goes under the seed tray
they aren't cheap but you can get them at nursery supply stores & of course on $bay
but one or two very small light bulbs the size used in nite lights will supply a surprising amount of heat
very similar to the bulbs in the older Xmas tree strings
I second the idea from Jo. I have some of the rope-type Christmas lights that do a good job of provide a little extra heat. I'm currently using some on my outside faucets during the record cold temperatures we're having in Texas. The lights, coiled around the faucets, covered with a small box, have kept all my faucets clear in single-digit temperatures. The boxes are just warm to the touch. I haven't measured the temperature increase of the string, but bet that it is enough for your greenhouse shelf.
FeedMe, I would not use regular Christmas lights- the bulbs could cause hot spots. Rope lights are encased in plastic and barely warm to the touch. Here's one photo of mine- I have since added a second set and they are doing very well.