Go for the insulation. 68% light transmission may well be enough and you could always suppliment with some lights during the months of darkest winter, but that extra insulation will also keep it warmer in winter, cooler in summer and lessen your utility bills.

I have only a double wall, so it's lined in heavy bubble and wrapped outside with a heavy solar pool cover and I use no lights at all inside, but still have sun loving plants blooming their heads in it.

But if I had known then what I do now, I would have spent the extra up-front and ordered the 5 wall. If you want to keep even a 5 wall really warm in northern climes, a pool cover is still a good idea, but the bubble wrap lining the interior is frankly a PITA to deal with and with 5 wall, you wouldn't need it.

Thanks birdwidow. You make a good point. I have read many posts where pool covers are mentioned but I'm not sure how they are used on the greenhouse.

Clear solar pool covers work as well on GH's as they do swimming pools and have become a common means of adding insulation to GH's in winter. They transmit light, but serve as a blanket to keep whatever heat is inside from escaping, while allowing plant growth and will allow sunlight to enter, to add additional warmth, then keep it in.

Most people who use them bundle their GH's up, leaving only a cut out for the door and if they don't have a direct vent heater, may also cut out for the roof vents, to allow them to open.

However, a pool cover large enough to wrap a 12 x 16, which is also the size of mine, proved just too heavy to handle, so we cut it in half, with one part overlapping the other. The two parts are held down over the center with a long cargo tie-down hooked to large, stainless steel eye screws permanently fixed to the GH foundation.

To prevent cold air from coming in under it, I have another long tie-down running around the bottom. It too is connected, on either side of the door, to more eye-screws.

The need for a cover in winter is really dependent on how warm you want to keep your GH and how much you would need to spend on heating fuel to do it. Adding that extra layer of insulation can make a real difference and in many cases, the cost of the cover will pay back in fuel savings over the course of just one really cold winter.

BTW: If you are planning a 5 wall, is it perchance a Cross Country?

Not to counter birdwidow's excellent advice, but I sometimes like to play devil's advocate. Depending upon how you plan to orient your gh on your property, it's likely that your north wall will not be important for light-transmission. This means that you could completely wall off that side and heavily insulate, effectively removing that square-footage from your BTU calculations.

If you did this, it's possible that you could get the r-value from your structure that you're looking for, without compromising light loss with 5-wall. Perhaps triple-wall would get you enough r-value in that case.

Consider the following, too, which might allow you to wall off other parts (perhaps the NW side, or small sections of the roof):

In my zone and location, it's been most beneficial to having a "long wall" facing east, instead of south...as most folks orient their greenhouses. This because the rising sun immediately starts heating the interior up following a cold morning in the winter. Since I heat with electric heaters, which are marginal at best, I need all the help I can get!

I don't need lots of light from the south side during the warmer months, as the sun is high enough to come through the roof anyway, in addition to the "short wall." This would be different for you, of course, but perhaps helpful to consider. I suggest this because, maybe, another design...such as a saltbox/lean-to, might combine the best aspects of light efficiency and insulation of unused walls.

Just a thought or two...

-Bruce

My current greenhouse is about 8x10 twin-wall Juliana. The north, east and west walls and north roof are insulated with Reflexit. The south wall has bubble wrap. For the most part it's fine, but given our winter temps I want to beef-up the insulation in the new greenhouse and 5-wall seems like a good idea.

A bit more info. The side walls of the Juliana are only 4'9. I am considering the Cross Country Artic and Cottage from ACF and BC or the Solar Gro San Juan and Rainier from Charley's. These models have side walls of 5'6". Here's a little complication. Last year I installed a beautiful 6 foot privacy fence, you guessed it, on the south side of the greenhouse. I still get plenty of light through the roof. The new greenhouse will sit on a three foot concrete wall to increase the amount of glazing above the top of the fence. Total height(depending on whch model I select) will be either about 12 feet or 15 feet. I'm short-5'1". Getting shade cloth over the roof and adjusting roof vents if needed will be a challenge.

Any suggestions are very much appreciated. I just don't want to make an expensive mistake.

I can't off any suggestions regarding roof vents because I don't have any but can give some tips on getting a shade cloth up by two short folk :>)

The peak of our roof is 14' and the g/h is 30' wide. My husband put very long ropes over the g/h. We laid the shade cloth on the ground, stretched out it's full length. We attached the ropes on each side and drug it - slowy - over the g/h. He then tied it to the sides to keep it from flapping in the wind.

The first year it took us several attempts and a lot of cussing. Last year it took us under an hour to get it up.

When considering your g/h height, a 12' ladder is the tallest ladder you can buy in big box store or at least that is the way around here.

Good luck and I wish I had the five wall!

Brooke

Regarding the energy efficient issue, I have only the south sloping side open to the sun with the rest is 2x6 insullated walls. That lets in plenty of light and heat. I really don't think ghs constructed so light can come in from every direction would be nearly as efficient. However, I am not fully up and running so my opinion may not be totally valid.

Regarding the shade cloth, I intend to lap the ends of shade cloth and sew them up to form sleeves and then slip pvc lengths into the sleeves and then put on 90 elbows to form tight rectangle shaped panels. Then I can place these on the south slope on runners raised 2-3 inches above the surface. I will need about 3 of these each 4 feet wide and 10 feet long, maybe more. I hope this will make putting the shade cloth on and taking it off easier, and I can leave one panel off if I want to have a hotter zone. In the winter I can slip the shade cloth off of the frame and store it. Hope it works. . .once I actually get to that I will likely find that I will need to modify aspects of the plan or add features - such as adding pvc constructed "U" hooks on the top end to hook over a permanent pvc runner at the peak.

It appears that my best option will be to go with the straight 5-wall and take with the reduced light transmission as a trade-off. I contated Charley's, ACF and BC to inquire about getting a south wall and roof. BC was very helpful and discussed all of my options with me in a friendly and professional manner. They offer the 5-wall with a twin-wall south side, but the heat loss would compromise the whole point of the getting the 5-wall. ACF dose not offer the option at all and I have not heard back from Charley's.

Does anyone out there have 5-wall? Do you find a major difference in the amount of light you receive? I would love to hear about your experience with it. I don't use the gh in summer so the plants will get high light outside during their peak growing season. But since I grow mostly tropicals including citrus, high light during the winter is important. I also have an orchid colletion that will be fine with the 5-wall.

Would still love to hear from all who have an opinion on the subject.

I'd suggest you talk with Kyle at BC about light levels, but am fairly sure that a 5 wall will transmit as much if not more light than my own 2 wall Cross Country, lined in bubble, which is clear but not totally transparent. Add the pool cover and I expect I'm getting far less than 68%.

However, I have a pot of ivy geraniums out there right now that are loaded with blooms, and an asparagus fern; getting ready to seed. All under super heavy bubble, under a solar pool cover that's less than clear right now, from snow and dead leaves that fell on the GH after we put the cover up, not to mention airborne dust, etc.

Birdwidow,

I'm starting to think that the way to go is with all 5-wall except for the south roof. That's where most of the light comes in. My greatest heat loss will be through the roof, but if I add a fan to bring down the warm air, that might help. And besides, I need the sun in the winter just as much as my plants do. Nothing chases away the winter blahs like going into a warm, sunny greenhouse. If I can't get that, then my enjoyment of the GH will be greatly diminished.

How do you like your Cross Country? Which model do you? You're in a zone colder than mine. What's your heating set-up and what min temp do you try to maintain?

Please forgive my ignorance here, but when you say 5-wall are you saying the polycarb sheet has 5 layers? I haven't seen anything like that on the market. I have been researching greenhouses lately and have seen double wall polycarb and one of the very pricey models has triple wall. I live in aone 7b and doubt that I would need more insulation than that, but I was just wondering if I am understanding this thread correctly. Cheryl

seamommy: Check out BC Greenhouses for their 5 wall, then price compare with their major distributors, starting with ACF and IGA. BC won't undercut their own distributors, but all of their GH's are built to order and- read on....

mulchlady: Mine is the 12 x 16 Anniversary model, in white and it's everything claimed. Sturdy and truly precision mfg. Once we had the foundation in and ready, it took less than 3 hours for 3 men, one of them an old poop, to have the frame completly up and secured. Every single part fit- perfectly.

But I use mine as a tropical fish hatchery, so went to extremes with the insulating to keep it at a steady 70 deg. min temp all winter. However, as a reward for those extremes, it's incredibly cheap to heat.

My heater is a 45,000 BTU dual vent Sterling. I probably could have gotten away with a bit less and yes, I know that because it's a bit more than necessary, it doesn't run as much so costs less to operate but will probably wear out the electronic ignition sooner, but one of them isn't near as costly as our natural gas rates. Everything is a trade-off. I bought it on the recommendation of the H/AC contractor who installed a new system in our home a few years ago. He is exclusively a Trane distributor so I believed his opinion would be unbiased, and he was right. It's excptionally well made, powerful and reliable.

But all gas heaters/furnaces need routine annual maintenance if they are to be counted on to keep running trouble free, so the one in my GH gets the same end of season cleaning and servicing as does the one in our basement.

Good. You understand the value of ceiling fans, but in a 12 x 16, not one- two. Two 52" outdoor rated ceiling fans from any big box home center will pretty much pay for themselves in one heating season, not to mention what they will do for you in summer, if you mount them directly under your roof vents.

It's late and I'm road weary, so will come back tomorrow, and tell you exactly how we mounted ceiling fans in a Cross Country. A hint: lengths of aluminum L stock from the local home center and lots of extra custom headed (to fit the polybars) SS bolts from BC. The SS nuts are a stock item at any home center.

But if you buy a Cross Country and fail to take advantage of being able to raise your ceiling with a taller knee wall, with a custom door drop at no extra charge, you are shooting yourself in the foot before you even begin.

Thank you to all who responded to my request for help. I made a decision and ordered the greenhouse. I chose the 12x16 Traditional 5-wall polycarb with a south roof twin-wall from BC Greenhouse. Great staff and excellent follow-up. I was able to place the order yesterday with delayed delivery until May. I am very happy with my choice.

I am comfortable with the energy savings offered with 5-wall and the amount of sun light I'll retain using a twin-wall in the south side roof. I also ordered the 12" fan exhust system and vent screens. I'll need other things as well, but right now I have a mild case of sticker shock even though almost everything was on winter sale.

Seamommy, take a look at the BC website. They have really helpful information on the different glazings.There is pretty detailed information on light transmission and R values.

Birdwidow, I cna't wait to begin using the new GH. Thanks for your input and support.

If I can ever get the darn photo function to work,(tried several times, can't do it) I'll post pictures.

Thanks again everyone.

Hello Everyone! Mulchlady hows your gh?? I am pleased to say that I also ordered from BC Greenhouse ....I live in the Cariboo in BC so I was able to drive the 7 hr trip and pick it up. I saved myself over $1200 after fuel for my truck. I ordered the 5wall traditional polycarbonate freestanding model its 12'8 1/2 x 16'9 1/2. Sounds the same as yours except for I covered mine all in 5wall. I am working on installing 2" xps vertically 4 1/2 ft underground to get below our frostline here.How did you make out? Crazy excited here in the Cariboo!