Heat is a major concern with the Rion kits. Their warranty certificate actually indicates in writing that Rion's warrantly does not cover damage due to excess heat. So if you go with a Rion, you will need to pay extra attention to temperature management. The Rion 8x16 I recently built, straight out of the box is a sauna. At noontime with no clouds, it was in the 70s F outside and it was breaking 120 degrees F inside. Shade cloth, fans and other supplemental cooling is a must. The HFGH has some drawbacks straight out of the box too, but there is a wealth of information on these forums on how to reinforce them to make them sturdier and more efficient. The price is also nice. For the price of one Rion, you can probably build 2 or 3 fully outfitted HFGH of similar size. You could set them up on brick or concrete knee-walls. But bear in mind that these are already tall units to begin with. The Rion stands over 8 feet at the peak, the HFGH is pretty close to that too I think. It is something to think about if you are in an area with high winds. I like my 8x16 Rion kit, but it is still too early to tell if it will age gracefully or crash & burn (or melt). I am willing to be the expensive guinea pig for everyone's sake :) Some metrics: (**Disclaimer this is NOT an expert opinion**) *Price: HFGH Wins - price difference is very significant. *History/Shared knowlege: HFGH Wins - I have seen a lot more informative posts about the HFGH than Rion. Come on Rion owners, you gotta share the knowledge :) *Sturdiness (Stock): Rion Wins - Straight out of the box, the HFGH needs some significant shoring up. The Rion has very substancial structure. This is assuming that both kits are properly anchored to the ground. *Structural Integrity (Heat): HFGH? This is just based on the assumption that aluminum will be better able to withstand high temperatures compared to plastic/resin combos. * Dead/Live Load: ????? - Rion claims that their GH can support a snow load of up to 1100lbs. I do not have data on the HFGH - can someone please fill us in? * Aesthetics: Rion Wins - It sure is purrty! :) * Expandability: ????? This is an iffy subject. You can purchase additional Rion "middle modules" to expand the length of the GH in 4 foot increments. But the price of the expansion kits will probably match that of a whole HFGH kit. So the decision becomes "Expand the Rion? or Build another HFGH?"

I've used everything from store bought seed starting mix to pure homemade compost and various mixes inbetween. The only times I've had problems were those times the mix was too heavy with some garden soil added and when the mix was too wet or air circulation was too poor. I'm a firm believer in whatever works for you. John, thanks for posting this picture and telling us about your results. In my experience some compost in the mix always gives better, sturdier growth. But I've never done a side-by-side comparison like this. Very informative!

szut, I have built both a wood framed and steel framed GH. First was the wood one. It has survived well but is in need of a repaint and recaulk which was part of the reason I went with steel for the second GH. The other reason was strength. Wood 2x framing is fine for smaller structures. But if you are trying to span longer widths, the size of the wood becomes prohibitive. Especially if you have high snow or wind loads to contend with (I have both). I think you will find Al for structural members is not doable for other than rather small sizes (hobby GHs, etc). Perhaps if you use built up Al girders, but that would be very pricey. Most commercial GHs use steel structures. I ended up going with steel tube arches from a commercial GH, which I made into a lean-to GH on the side of a barn. Given the structural loads it had to meet (50# snow and 135mph wind) it was relatively cheap (no doubt would have been cheaper in less extreme environments). IMO if you can build with wood 2x material, making the transition to steel tubing should not be that hard. You'll need a few new tools (metal saw and drill), but in many ways it was just like working on a big erector set. As a cost saving, you could look into buying a used commercial GH, or at least the frame. That could give you the structural material at a very inexpensive cost. Something that is harder to do with wood 2x material. My steel GH is too new for me to say how it will fair on the maintenance side. But I expect it to handle the moisture better than wood, although it will need some touch up painting no doubt in time.

Julia, Personally, I'd lean away from using the wood base instead of the Riga base kit. You make a good point about pressure treated lumber, which for me would be a dealbreaker (but that's just me - I grow food plants right up against the edges of the greenhouse). If you didn't use pressure treated lumber, then you'd be using cedar or something like that, which lasts maybe 10 years buried in the ground and your greenhouse will last a lot longer than that. For longer lasting wood you could use ipe but that would cost more than the base kit. The frame doesn't have any gaps in it, at least not big enough for a mouse or a snake. The warranty does not cover hail, but your homeowner's insurance covers that. I am not certain but I would guess the warranty would protect against cracking or really bad, premature yellowing. They will all yellow a bit with time. As for price comparisons, you are correct that the various vendors make it tricky to compare. One strategy would be to decide what you want, then price that option at each store. I think 2 roof windows is a very good idea for the Riga IV and you could do 2 or 3 for the Riga V. I don't know the translation of "grand" vs IV or V, but you can figure that out by looking at the dimensions. Of course shipping is a big factor too. I think the comparison shopping will get easier as you narrow down what setup you want.