-18 last night. Still sub 0. Still a steady +70 in the GH.

But it's also one of those brilliantly clear, sunny days and even if bitterly cold, the sun reflecting light off the snow makes it rather a sparkling winter wonderland.

Of course, that's strictly a view though a window from inside a warm house. If I had to be out in it for very long, it wouldn't be so enchanting.

It hit -13F this morning here and the greenhouse hit 42F...not too bad for a propane heater & small electric heater...although some of the tropical plants aren't too happy about it.

With two heaters, I always have a backup...good thing too, because yesterday I went out to find the pilot on one had gone out and the GH was down to 44F. Usually this time of year I strive for 55F. Lit right back up, though. First time that has happened, I think.

Big test tonight: temps here are to fall to 20 degrees.
I know that doesn't impress those of you in colder zones,
but we're not supposed to get this cold here for so many consective days.

The cat and I had lunch in the greenhouse today, where it was a warm 78 degrees; 41 outside.
{{gwi:286638}}
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Nell

I feel for you greenhouse folks. I don't have a greenhouse (I wish!) but it got down to -2 F last night here in the Hudson Valley of N.Y.

It went below 20 last night. The 3 small electric heaters kept the Rion at 60F. The HFGH is empty right now.

The low temp this morning was 4.5 below! The greenhouse is sitting at 55. The roses out there must think they're in Florida. :)

I hear ya, Nell. I took my beer out there the other evening, and finished it sitting in my chair in front of the heater. It was almost like hanging out by the fireplace. The only thing I was missing was a cat in my lap -- mine are indoor cats, and my barn cat won't walk on the gravel to come into the greenhouse. She sits on the threshold and meows at me.

Connie

Yikes cold in WI too. Backup kerosene and gas heater running. Kepping it at 60 for low. Trying to start some tropical seeds. Some are up : )Stay warm one and all...

Yep, been down in the low and middle teens in suburban Birmingham. I heat with kerosene. I can keep the 22'L x 9'W x 10'H greenhouse at 60 degrees with two 10K BTU heaters. At 20-25 degrees, one heater will keep it at 50 degrees. I don't know about y'all, but global warming hasn't been seen here, not this winter, anyways. I've already spent more on fuel than last year and it is cheaper this year.

My heater failure the other day did give me a chance to calculate my structure's overall R-value. I had one 24K vented heater and one 1500W cheapo from WM. So assuming 80% efficiency from my propane heater and 100% efficiency from the WM cheapo, I had 24,320 BTU. Surface area of 1116 square feet. Then I plugged those numbers into a GH heater calculator, and if I try a few numbers I get a U of 0.52. That translates to an R-value of 1.92.

Maybe someone will point out an error in my calculations, but if not, then I have to think that isn't TOO bad given that I have a single pane tempered glass structure so I started with an R-value of 0.88.

I'm sure I can't touch BW, however.

Sure you could Stress, but why would you need to? Keep in mind that I'm using my GH as a tropical fish hatchery, so fitting it out to hold a minimum temp of 70 deg. regardless of the weather was an absolute requirement or I couldn't use it for that purpose at all.

We had 2 mornings last week with 2 BELOW zero. We had a heat wave today, mid teens with 3 inches of snow!

COME ON SPRING!

We hit an outside low of -18F Friday night and saw an interior greenhouse low of 39F (measured at the floor level). We didn't bump up our propane heater thermostat to match the weather (which we could have) and still did ok. Keep in mind this is an all-glass lean-to greenhouse w/no insulation (zone 4-5). I'm sure we'll pay for it in propane but so far so good. About a week ago we started some salad micro-greens from seed and almost all have sprouted and are doing well. We MAY consider a solar pool cover next year just to keep the temps even....but...with out greenhosue being a lean-to style I can't envision a nice/neat way for the solar cover to cover the roof & three sides. Also how do you account for the roof vents trying to open with a heavy solar cover on top?? Any suggestions?

Fuzzymoto: Is your GH attached to a wall on your house directly under the eaves of the roof, or against a high wall?

I'm asking because I can think of several possibilities for holding a pool cover on it, but without knowing; really can't make a suggestion that would fit with the actual structure.

But the roof vents are the easy part. If your heater doesn't exhaust directly to the outside and isn't one that burns only fresh air, then I can see why you would need to be able to ventillate. Otherwise, leave the roof vents closed under the cover in winter and just crack the door a bit to cool it down if it overheats.

To be honest, opening roof vents in a heated GH in winter is surely the best way to waste heating fuel I can think of but if you truly do need the roof vents to operate in winter, just cut the pool cover around them, then use the shrink film sold for windows to insulate them on the inside.

If wrapping the GH with a pool cover proves too much of a hassle, you could still insulate with bubble wrap and take advantage of the fact that with glass, you have far more options in holding it in place than those of us with polycarb enjoy, starting with the ability to just lay a light bead of adhesieve on the glass, or line the edges with double faced tape, something pretty dicey to attempt on polycarb, as there is no safe means of using any type of adheseive solvent on it.

If you do end up lining the interior with bubble, you will find that it insulates against summer heat as well as winter cold. I don't think I'm alone in having lined the interior of a GH with heavy bubble wrap then left it up all year. It's amazing how well everything grows in the resulting bright but diffused light.

Hi...yes it's attached to the wall of our house. It is technically under the eaves but the distance between the top of the greenhouse and the eaves itself is probably 10+ feet. It's a pretty high wall. I'm sure I can probably fashion some sort of attach points, my concern is more for the shape of how a rectangular pool cover will fit on the odd shape of my greenhouse. On a normal greenhouse it fits cleanly over the top. With the shape of mine there's going to be a lot of slack pool cover because of the irregular shape. I'm not sure how I't deal with the extra pool cover on the lower ends (perhaps folding it like wrapping a package.

My heater is direct vent, but even in winter we get some pretty high temps that the roof vents do open. I'm not home to open the door to vent, but perhaps I can hinge the pool cover to match the roof vents.

As far as bubble wrap I've pretty much ruled it out as a global solution for my GH. Mine is 16 x 10 with a big lean-to roof. Even with an easy attachment method it would take days of work on and off ladders to bubble-wrap, and as far as leaving it on all year we'd bake our plants and ruin the view thru the greenhouse that we love.

I'd be open to trying to fashion a solar pool cover to cover the roof and much of the side walls, and perhaps bubble wrap on the smaller low front wall only.

It occurs to me with 16-feet wide and 12-foot roof peaks the solar cover would have to be 40-feet long and about 12-feet wide. Do they make such a size?

Do people cut various sections of pool cover to build a cover to match the greenhouse shape, or simply flop it over and tuck in the excess pool cover slack? I guess I'm wondering if it would be best to buy three pool covers and cut them to the shape or try to buy one huge one and wrap it all over the place.

Anyone else with my shape GH using a pool cover??

I've added a link to a picture so you have an idea of the shape. That's not my greenhouse or the size of my greenhouse but just an idea of the shape.

Here is a link that might be useful: {{gwi:286637}}

I've found that there ARE large solar pool covers. I guess I'm just curious how to wrap a greenhouse shaped like mine without it looking awful or without having all sorts of slack sections flapping in the wind.

Fuzzy:

You can get pool covers to fit an Olympic sized pool, or a GH many times the size of yours, but if it was of the weight you need to use on a GH; a minimum of 12 ga., you would also need three large buddies and several gorillas to get it up there. Those things are heavy, and why all but the smallest ones actually used to cover swimming pools are wound onto huge rollers.

You could use 3 smaller cover pieces, but due to the shape of your GH, if you want to avoid the over-wrapping, would then need to cut the side pieces to fit, then connect them, to make a custon fitted cover. Given careful measuring and perhaps taping pieces of rosin paper together to make a pattern for the ends, then riveting the cover pieces together, it could be done, but would be a real chore.

Another option would be to use bubble wrap only on the interior end walls and a single length of pool cover only over the top and front, which would give you effective insulation where you most need it; on the roof and the longest wall.

How you would attach it to the top edge of the GH is another matter, but there too; there are options and as installing then removing the cover would be a bi-annual chore, I think it's worth while to set it up to make it as quick and easy as possible, even if the set-up part is a project.

For instance: Order a long enough length to give an extra ft. to wrap around a long 2 x 4. Then tack or screw the cover onto it and install some large eye screws in the wood to fit onto hooks you would install on the side of the house just above the top of the GH.

Or, some spikes, possibly long, large stainless steel hex screws set at an upwards angle, with holes drilled into the 2 x 4, large enough to slip onto the screw heads. Once in place, with the bottom of the cover held down, it's not likely to come off until you and a helper stand on either end and lift it off.

However, you should still allow for wind to get under the edges at the sides, so you would still need some means to tie it down and for that; more eye screws, permanently installed along the base and rope, or long bungees, or a combnation of both.

We use both long bungees and some long cargo tie-downs to hold the pool cover on my 12 x 16 x 12 ft. GH and while the lines running over and around it aren't all that elegant; they do the job.

Just some thoughts. Keep asking and hopefully, someone with a pool cover wrapped lean-to will come along and tell you how they did it.

Thanks. I had not thought about the weight. I was planning on a 14ml or 16ml cover. The size would most likely be in the neighborhood of 45-feet x 20-feet.

Anyone have any idea what such a cover would weigh?

I'd allow enough slack to attach wood to the cover. I have wood all around my gh as an easy attachment/anchor point.

I suspect we'll go with the foldover method and find a way to tape down the slack (is there tape that will work?)...but now I'm not sure the wife and I can hoist such an animal up onto the GH. How heavy are they?

Fuzzy: It's not just the weight, it's the weight coupled with the sheer size. Unless you and your wife are both weight lifters, trying to wrestle it up onto any height much greater then your own heads could put both of you into back braces.

I have a notion, but before I even offer it:

How high is your GH at the peak and what kind of roofline; straight or curved eave? Also; are there any points on the frame where you could install medium sized eye bolts on the exterior?

The peak of the GH roof is about 12-feet off the ground. The GH is straight eaved roofline. It's aluminum framed do as much as it's easy to install eye-bolts inside, it's pretty difficult if impossible outside. I've also sort of ruled out trying to build any sort of roller. I'm actually hoping if we can wrestle it up on the GH, wrestle it into the shape we need, tape/secre the excess, attach it to the wood around the GH---all in a way that when we remove it it will stay in that shape and be easier to install in subsequent years.

Seems like cutting three individual pieces would create the lightest weight cover but be a bear to attach the three pieces and cut them accurately. One big piece folded into shape will offer the most secure/insulated solution, but be a bear to install.

Perhaps I should consider starting a thread people with lean-to GH may fnd easier so we don;t wander so far off topic here.