A few thoughts; the Harbor Freight 4mm twinwall polycarbonate panels (made in China) are lower quality than twinwall polycarbonate you would buy from a greenhouse supplier. They don't seem to have UV protection. I have a HFGH 10x12 and my panels last 3-4 years here in the sunny south before they deteriorate (I am replacing them.) Most twinwall poly from greenhouse supply places has an approximate 10 year warranty and one side is treated for UV protection. Single pane glass will lose the heat much more quickly on cold nights than twinwall poly, so you might save on panel cost, but you might also then be having to pay more to heat your greenhouse. This heating calculator might be helpful in comparing the performance of different greenhouse materials: Heat Loss Calculator For my two cents, I'm wondering how much you can depend on adequate heat being gained into the greenhouse through your house exterior wall, but others will probably have better insight on that question. The idea of storing water in black barrels for heat mass gets mixed reviews in this forum; many folks say that it's not effective, especially in small greenhouses, where space is better used for plants. I've read that the heat stored in the water can help raise the greenhouse temperature for a while, but by the critical coldest hours before dawn, the heat benefit has been lost. You might seek out archived threads on this topic (just giving you a heads up.) I have not purchased the HF vent openers, but I recall that past posts here have not been very positive about the quality. My guess is your idea of spending more to buy better ones might be a wiser move. From a cosmetic point of view, I'd think your carpentry skills would allow you to build an attached structure that would look more like an actual improvement to the house than attaching the HF structure. It would allow you to install a more traditional door, too. My Harbor Freight sliding doors work OK for my purposes, but if you'll scan the archives here, you'll find that some folks don't like them in winter weather (the tracks can fill with ice and freeze shut if conditions are right.) This has only happened once to me during a record winter storm, but I live in a warm climate.

Clare, I really don't know, but here's a thread from February discussing the same question. It sounds like it may be possible to order from Harbor Freight, but I wonder if the cost is prohibitive. You might call the toll free number to find out cost with shipping. I hope it's workable! HFGH replacement panels Sorry to hear about the 90 mph winds...I hope you didn't lose any plants.

In his blog about building his new 6x8 HFGH, dewey1945 shows how he applied 6 mil UV resistant plastic to the outside of his panels. I havenâÂÂt seen this idea discussed anywhere before, so IâÂÂm interested in following his blog: Apply the UV Resistant Skin When I replaced my roof panels in October of 2011, I applied a clear marine coating product to the outside of my new panels, before installing them. I also applied the same product to half of a scrap of HF polycarbonate (left over from installing my exhaust fan.) IâÂÂve left it exposed to the sun since October 2011. So far the treated side still looks shiny and clear, while the untreated side has started to look a bit dull and cloudy. Might be a good sign, but I think itâÂÂs still too early to tell if this product really does help. My cost to purchase a gallon of the product was around $100. The company (Top Secret Coatings) seems to have changed their product line since my purchase, so IâÂÂve emailed them to ask which product is the current equivalent of what I used. IâÂÂll post back here as with that info as soon as they reply. ItâÂÂs too bad we have to wait at least a few years to see if ideas like this truly will help extend the life of the HFGH polycarbonate panels. From my reading, folks in southern states with intense sun seem to report more panel failure. The topic hasnâÂÂt come up here at GardenWeb for a while, so IâÂÂm hoping that means folks in other climates arenâÂÂt having nearly as much of a problem. If you donâÂÂt do anything to protect your panels, and notice some problems in years to come, you can order replacement panels from Harbor Freight. The HF panels wonâÂÂt last as long as higher quality twinwall polycarbonate from other supply companies, (with real UV protection,) but they do cost a lot less. FYI, hereâÂÂs a summary of my pricing research from October 2011, for just enough material to replace the roof on my 10x12 HFGH, including shipping to my state: Farmtek 4mm twinwall polycarbonate, approx 10 yr warranty, about $410 Solexx 3.5 mm, (a flexible translucent white greenhouse covering material) about $350 Harbor Freight 4mm panels, $135 IâÂÂll be sure to post back with the Top Secret clear coating product number, so itâÂÂs recorded here for the thread.

Hi steve333, good question. I always said I'd never buy HF panels again, but when I was faced with the purchase, I caved! It was a combination of price, and convenience. At the time, I priced 4mm twinwall polycarbonate at a number of greenhouse supply companies. The best price at the time was through FarmTek (cheaper than Charlie's or any other source I tried.) Their product had a ten year warranty, and was truly UV-protected. However, the cost to purchase enough material (just for the roof) with crating and shipping fees to my address, was $410. The cost to order more Harbor Freight roof panels, with shipping, was $135. That difference was enough to give me pause. Hmmmm. Note, it's possible folks living closer to urban areas with more businesses would have found better deals on shipping, but down here in southern NM, the only things close to us are lizards and cactus. Also, the HF panels arrive sized to fit; if you buy better polycarbonate from a greenhouse supply company, you'll have to cut the material to size yourself for each part. Not difficult, but it does take time, so I factored the convenience in as well. Also, occasionally I consider upgrading to a larger home-built greenhouse, so kicking the can down the road doesn't bother me as much as it would if I was positive I wanted to keep this small greenhouse another ten years. I think an argument could be made for both sides. If rtyu's and my experimentation with the Top Secrets clear epoxy product pans out, though, it will definitely tip the scales towards using the (clearly lower quality) HF panels and protecting them with the coating, especially if folks can apply it to their new greenhouses, and avoid the need for panel replacements. Fingers crossed. I think much of the appeal of the Harbor Freight greenhouses is cost/value. They appeal to folks who want to try greenhousing but don't want to make a major investment. I haven't tallied it up exactly for a while, but scrounging supplies, materials, and labor, I figure we have around $2500 in ours total, including kit, benches, sink, plumbing, electric, heaters, thermostats, shadecloth, pavers, and the new roof panels. Over six years that's roughly $400 a year (not including heating costs, which aren't too bad in my climate.) So I think many folks who are attracted to the HF structures also enjoy keeping costs low. It's just one option in the world of greenhouses, and not the right fit for everyone. Happy New Year!