You're correct...installing it on the outside will not be good. I would think you could just install it inside with a couple of long curtain rods and hooks. One rod would go at the high point where the greenhouse joins the side of the house, and that's where the hooks would go. The other rod would be attached where the GH roof meets the sidewall and you would simply drape the rest of the fabric over it so it hung down straight. If your greenhouse is really long, you could use several rods. If this doesn't work, it would help if you described the geometry and size of your greenhouse.

I have done that for my 6 by 8 palmram greenhouse a 5 inch line from the furnace in my shop. kind of helps probelm is my shop is so well insulated that it only comes on a few times each night and even with my electric heater it never got over 11 C at night and we are not even in minus temps yet, So I buildt a bigger one and used a 50 gal heat sink heated with 2 fish tank heaters and it keep the room at around 55 over night and when I run water through my table in tubes the tubes stay around 65 to 70 F all night long, we had minus 2 last night with no change.

Hi, I don't have experience with removable roofs but I have some other ideas . . . Have you heard of using phase change materials to control temperature extremes? Here is a blog about it: http://greenhousefashions.blogspot.com/ The blog is written by some people at a company that sells phase change materials for other more conventional applications and the blog is meant to show that PCMs can work great in greenhouses too. We are building our greenhouse now and considered installing PCMs but decided to wait to see how our greenhouse functioned without them first which will help us in estimating how much PCM material we need. Another reason why we did not go with PCMs immediately is because we are building a Subterranean Heating and Cooling Storage system into our greenhouse which is a phase change system. It is possible we'll have all the heating and cooling we need from the SHCS. For more information about SHCS see this blog: http://www.roperld.com/science/ymcasolargreenhouse.htm Have you looked at "Pit" greenhouse designs? That could really help maintain temperatures passively: http://www.amazon.com/Earth-Sheltered-Solar-Greenhouse-Book/dp/0960446400 Here is another great book. In it, it talks about a variety of passive solar designs that work well. The best combination of strategies seems to be an attached passive solar pit greenhouse: http://www.amazon.com/Solar-Greenhouse-Book-James-McCullagh/dp/0878572228/ref=sr_1_7?s=books&ie=UTF8&qid=1385082426&sr=1-7&keywords=passive+solar+greenhouse One thing that I wonder is if you should glaze the roof at all or at least do it minimally. We opted to go with really tall south-facing windows, a few skylights and tons of insulation. This should help with too much solar heat gain in the summer (along with the SHCS) while allowing more solar heat gain in the winter when we need it. For a short article from a green building site that is focused on energy efficiency see: http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/sunspaces-solar-heat-and-place-grow-plants In case you don't already know about this, check out this site that has tons of peoples' experiments with all kinds of solar greenhouses: http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm Best of luck! Looking forward to hearing what you end up designing. Where are you located?

Cape Cod has some of the highest electricity rates in the country. From what I read, you pay 17 cents per kw hour. Your 400 watt light would be .4kw, making it 6.8 cents per hour for you to run. That's about $50/month for you to run that light. And if you're also buying kerosene and running through a gallon or two per night, you'll spend twice that much in fuel. Artificial light is too expensive if you're poor (like me). So is heat. If you want to make something from nothing, grow cold-weather crops like greens over the winter and seedlings for your outdoor garden in the spring. If you want heat, the most economical is a low-wattage heating cable run through a raised bed. It will provide just enough heat so that at least the roots don't freeze. fwiw, I use wood heat, but I'm in a rural area and get firewood for next to nothing. It's not practical for everyone, but it is the cheapest way to heat a structure. Good luck with your project.