Millet:

If you don't think you can run 40-45F at night in winter please tell me why not. What am I missing on my citrus by not running warmer? I can't run this house warmer but have considered putting up another greenhouse just for the really low chillers and heat lovers; citrus, figs, grapes, etc. That way I could lengthen the season by running days warmer even if I didn't run nights warmer.

fruitnut, your correct, one could easily grow citrus at 40-F night temperatures during the winter, and the trees might even enjoy it. In fact growing citrus at 40-F during the winter months would probably produce a more abundant spring bloom, and better peel color then growing at higher winter temperatures. Besides citrus, I also grow a large collection of orchids (many winter blooming), cacti, pomegranates, figs, vinifera wine grapes, papaya, many pineapples, tomatoes, plus various flowering plans. As you say, having a small greenhouse for high heat loving cultivars, and a larger greenhouse for varieties that can withstand lowers temperatures, would be more economical. Even a compartmentalized single greenhouse might work. - Millet

Millet:

Thank you, I understand better now. I've thought about a compartment that I kept warmer say to start figs sooner in spring. One year I did put blueberries on top a platform at 8.5 ft height. Up in the warm peak. It maybe gave me a week or two earlier bloom. But getting up there and keeping things watered was a bit much. I didn't relish falling off.

Just having one greenhouse is a blessing! Best money I ever spent.

My greenhouse is a double wall air inflated Nexus Corporation greenhouse. Who is the manufacture of the one you have? - Millet

Mine is a Stuppy, powerhouse diamond I think. It's over built with 12000 lbs concrete on each side. They wanted piers for each main post of 16 inch by 60 inch. I couldn't do that so poured a solid pier on each side.

If doing over I'd reduce height from 16ft to maybe 13-14ft just because it would be easier to cover, etc. I'd increase the height of top of wet wall and fans from 7ft to 8ft. This would fit the height of my crops better. But honestly I've seldom seen heat damage on any fruit at the top of the canopy.

Mine is double inflated poly. First two times were normal IRAC both layers. Just finished yesterday installing double layer woven. Solaroof 172 over Solarig 140 bottom. I like it after it's up but it was a real struggle because it's so stiff. Glad it was warm. We let it set several days after getting in place. Were able to tighten another 4-6 inches lengthwise after setting. It has a 6 year limited warranty, very limited. It does appear very strong and shouldn't be bothered by hail or high winds. The regular poly both lasted 3.5 to 4.5 years but were barely inflated, or the last totally uninflated the last two years because of hail and tearing. I think the last tore because I stretched it too tight on initial installation.

Sides and ends are corrugated polycarbonate. Great stuff. Mine is the clear. If building another in this mild climate I'd be tempted to install Solarsoft 80, 85, or 90 corrugated polycarb on the whole thing. But that would increase heating costs.

Both our greenhouse are very similar. My south end wall and both side walls are twin wall polycarbonate. The north wall is solid with its inside painted white, which reflects a lot of light back onto the crop in winter when the sun is low on the horizon. The top is double inflated polyfilm. Until reading you lastest post, I have never heard of Solaroof 172 over Solarig 140. I need to replace the top before winter (it is not 4 years old), and will look into Solaroof material. Thanks - Millet

The solaroof material is highly diffusing more so than the IRAC I last used. They claim 88% PAR transmission. Just guessing but I'd put it at more like 70% one layer or 50% two layers. I like the light level without the 30% shade cloth I had over the old stuff partly as hail protection.

You might look into Solar Ice. That was my second choice. Said to keep warmer at night and cooler by day. I want a really high light level without overheating. Solar Ice over IRAC without hail netting might do that.