When you said your budget was $600, and you had a $300 gift card, I added the two together. Given the materials you have, it's possible you may be able to build a suitable structure, but without knowing your design or available parts, your guess is as good as mine. Don't forget the moulding and tape for your Solexx panels -- they can be pricey. In order to calculate your BTU requirements, you first need to decide what sort of plants you plan on growing. Will it be a seed-starter, or year 'round structure? Knowing what you plan to grow will give you your minimum interior temps during the winter. Use the USDA hardiness zone map to determine your lowest possible ambient winter temps. There are online calculators available to give you your BTU requirement. In a structure as small as yours, I would go with a vented propane heater...if propane is your choice. The one you refer to is most likely non-vented, and you'd have fume issues. I think if you're insulated well, one or two 1500-watt electric heaters would be less problematic. If the structure is to be used only as a gh, then don't shingle your roof. (Again, I'm guessing. You mentioned shingles in your original post.) Link to the Solexx prices I mentioned is below. -Bruce Here is a link that might be useful: Solexx panels

""It looks like you've stapled and strapped the poly to each framing member - how was that worked out with regards to expansion and contraction? Any rips at the location of the staples? "" Not to each framing member, The roof is just secured along the edges. The front is secured at the ends and the middle and the side walls are secured at each strut. There are no rips at the staples because....... 1, Pull the poly tight and bang in a few staples. 2, Stick exterior duct tape on. 3, Go crazy with the staple gun! 4, take a 4ft length of non-pressure treated lath strip you painted with a couple of coats of latex paint. 5, do a squiggle of the cheapest latex caulking you can find. 6, Nail that over the top of the duct tape (only use one small nail per foot It is easier to get it all back off afrer 4 years when you change the poly!)) NEXT TIME!!!! I am going to install channels and wiggle wire. In the long term it is more cost effective. Repeat steps 1 - 6 for the second layer of poly. ""Getting to your kneewall, the poly looks flush, and the strapping over the poly appears to overlap the plywood without offset - was it notched to make it flush with the wall?"" Because there are two layers with a 1 inch wide by 1/4 inch lath strip and caulking in between the top poly layer looks flush. ""Overall, how do you like the performance? I plan to paint mine white too, what paint did you use? Any hindsight-insights you want to give to someone that appears to be going to down a very similar road? heh"" I like what I built. I do not really use it as a greenhouse as you can see by the junk in there. However for a gardening purist it is technically a double layer poly covered greenhouse with an insulated north wall and part of the north roof. I just used cheap exterior latex. You have to remember that even though the inside looks like it is inside because of the humidity and heat the conditions in there as far as paint goes is worse than being outside! Paint the wood with a couple of coats of whatever before you build it!!!!! Painting it all two or three times once built is a real pain. ""What is the overall height of your greenhouse? "" I layed down an 8in high base of cement blocks on the existing base I had, the side walls are 6ft and using that calculator (It is dark outside I ain't going out there) the roof triangle bit is 4ft high. So it is 10ft 8in tall... ""Would you have considered building your greenhouse with 2x2s?"" Yes I would consider it. Knowing what I know now my greenhouse is way over engineered. The plan was/is to extend it another 28ft. The extention would be a garage and workshop. If you look at what was there before I built the first part you can see what I am aiming for. That is why my greenhouse is so high. The completed building is the right height to insert a standard garage door. Also that is why the ends of my greenhouse look different. The end with the door in it is "temporary" that is where the extention will be. ""How far apart are your 2x4s spaced?"" 24 inches, the idea was to cover the greenhouse part in polycarbonate and the garage part in conventional sheeting and siding. If I was to build a new greenhouse covered in a double layer of inflated poly I would seriously consider a 3ft or even 4ft spacing like you see in hoophouses. After all we are just building a wood framed "hoop" house.

I built a similar 12x12 greenhouse from 2x4 treated lumber, but I painted after framing before glazing. Don't forget to use a good oil-based primer coat before painting. I have been through 2 years including 60 mph winds, 8" of snow, and 100+ F summer temps satisfactorily. I have some suggestions for you to consider. First, most GH owners would recommend twin-wall polycarbonate glazing. Second, you can stiffen and insulate the greenhouse by covering north wall with 1/2" treated plywood with 2" foam insulation panels. They come in 2'x8' panels which fit nicely if you space your 2x4s properly. You can do the same (with smaller benefit) by enclosing the bottom 2-3' of the side walls (as kneewalls). Little useful sunlight enters here. Third, with these changes, you don't need diagonal braces. Nor do you need cross braces on the rafters if the 12' peak length is not exceeded. I recommend using galvanized nail-on straps (not sure what they're called) at the peak and other ends of the rafters to hold the joints together. With primer and 2 coats of exterior paint, these have held up well so far. Now for condensation, venting, etc.... you will need good internal circulation fans to reduce mold/fungus problems. I think you will want the roof-glazing to overhang the sides by ~1' to keep rain out. Also, I think you will want to attach the glazing panels to the exterior of the studs/rafters and cover the joints with aluminum T-bars. Then, seal the seams with silicone. I suggest you look at the construction details at http://www.cloudtops.com/polycarbonate_verolite.htm. You will also have to provide some means of maintaining high enough humidity when you heat in winter: misters, foggers, etc. If you plan to keep any plants in the GH during summer, you will need shadecloth, misters/foggers for cooling, and larger exhaust fan. Other thoughts on your specific questions: By windows I think you mean roof vents. This will be needed for summer use. See how on-line GH vendors do it, especially the automatic open/close devices. I built mine from 1x2s but I have trouble sealing from rain. The glass/aluminum door is fine. Check your local building code or hire a licensed electrician to do the electricity business safely/legally. I will gladly answer questions and will welcome comments by others correcting or improving upon my comments.

My best advice is to figure out how big you can afford to build...then build a little bigger! You may think you only want to grow one mango or one lychee. You won't. You WILL want more! You want a good, tight frame utilizing thermal barriers. NY winters are as much a bear as Ohio winters. Keep that in mind. Build something somebody in Virginia or Georgia put up, and you'll be spending a fortune to heat it. Same goes for the covering. Glass or poly. Glass is more expensive but IMHO much better, more efficient, and a more beautiful look. Either way, it must at least be insulated, double-pane glass, or multi-pane poly. A bigger structure is more efficient to heat and cool than a smaller structure. Gas is less expensive than electric...for us. I use two stand alone gas heaters not dependant upon electricity. Depending upon what you want to grow, you may need to look into boosting humidity and how to cool it down. Don't forget venting. Attaching the structure to the back of the home is cheaper to build and gives you one insulated wall...equates to lower heating bills. Does the rear of your home face south? If so and it can be attached, look into this option. Make full use of the sun. Take your time and make decisions based on research and fact. Don't half-ass anything, you'll regret it.