Quote:
Originally Posted by bencelest
Richard , can you tell us more about the greenhouse heating cable ? ie where can you buy them? What brand? etc....
I am also skeptical as to the heat it can generate.
I believe someone posted in another website regarding this a couple years back that it did not give enough heat for the plant. I maybe mistaken though.
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The greenhouse heating cables I've seen are not for heating the greenhouse but for providing more heat at a specific location. The greenhouse itself has its own (typically gas) heater. So I wasn't surprised that someone was disappointed with the performance in an unprotected outdoor situation.
Also, Benceleste and I are in zone 9, so outdoors we are really only fighting a 10 or 15 degree (F) difference between low overnight temperatures and the lowest temperature we want our tropicals exposed to (45 deg F). IF I lived in a colder climate (e.g., where I lived in McKinleyville, CA or in Denver, CO) I would have a greenhouse and grow bananas and other tropicals in tubs on an insulated floor.
I have seen the greenhouse heating cables advertised in catalogs that arrive here every month or so by postal mail. I'll search around in the recycle bin for one.
CookieCows was asking about how I would insulate the walls. So far the cheapest solution (but the most labor intensive) is channeled cinder block stacked 3 high; they measure 6" wide by 8" high by 16" long. I would mortar them together, but fill them with R30 insulation instead of concrete. The heating cable would run down the channels. The bottom bricks would tarred to a 6" wide strip of 1" thick rubber matting that is used in construction. The top of the bricks would also be sealed off. A temperature probe would also be placed internally, but at some distance from the heating cable. I think I would set the cable to come on when the temperature drops below 50 (F).
To find out if the cable is necessary, I am currently building another raised bed but for a non-tropical plant. I am going to construct it without a cable, but with the temperature probe and measure what is going on.