I'm building a greenhouse from scratch. Partly because my wife wants it. Partly because I think it might help with the figs ripening here in Pittsburgh. The base is up and the walls are framed. I'm going to frame the roof tomorrow. So I need some advice. Does anyone have experience with the clear roof panels Lowes sells? Worried those won't last. Considering upgrading to a multi-wall polycarbonate. Opinions appreciated. If anyone knows a better place to buy that would be great to know too. Thanks..Tony

I don't know, but I wanted to offer you encouragement anyway :)

You're gonna have a lot of fun with it once you're done!

I build greenhouses for a living. Cheapest is two layers of poly 6 mill 4 year inflated with a blower.

You want something that diffuses the light. Both 6 mil poly and the polycabonate panels come in types that add some diffusion.

If double inflated 6 mil 4yr poly the inner layer should be diffusing often called IR. It also reduces heat loss at night. The outer layer should be clear.

Diffused light is more efficient because it penetrates better to the lower leaves and evens out shadows.

Hey Tony, I built a lean to greenhouse last year I used the fiberglass roof panels from Lowes and I am very happy with them This is not the first time I have used them, I have some panels over a large opening for a basement window and it's been there about 14 years and it is still as good as the day I bought it, as for the roof on the greenhouse I choose the white over the clear the stuff is very strong when applied correctly if you use it don't forget to use the wavy strips it helps to support the roof and of coarse the screws with the rubber seal the nails are no good they pull out hope some of the information helps 

 

Thanks. I don't want to spend a fortune. But I want it to last at least 10 years. So I think I'll have to go with something like corrugated clear plastic or twin walled polycarbonate sheets. Any ideas on that. My wife will have to look at it right out the kitchen window. So, as she said "it's gotta look good" too. Thanks

Most of the houses I build are out of polycarbonate and I can't afford it for myself. We use it at schools because of it's durability.

Glad I asked. I wasn't aware that I didn't want clear. So if I go with the Lowes stuff like Dave get the translucent? Btw, nice job Dave.

Hershell thats why I still have plywood on the walls as I find a deal on it I will put it in I did happen to find some amber and red plexiglass I thought it would add a nice touch and besides I get enough light through the top for what I am doing 

 

Dave, do you move your figs outside in the summer or do they get enough sunlight in the greenhouse to fruit?

I move them all outside the ones that are in there now are either air layers  or cuttings anything needing rest and relaxation I did leave the Jolly Tigers in all the doors were open and they just enough sun block not to burn up 

I've wondered about reusing the large sheets of corrugated plastic used for political signs. They seem ideal for greenhouses and are potentially free after an election.

Dave. It's too bad your not closer. I said it was expensive, I didn't say that I have a stash of twin wall. Now I know where all of the JT's hang out.

So Dave you get enough light with the white?

Hey Tony,I have also used the clear fiberglass sheets from lowes,its holding up great and the plants love it......and in the summer I add the green shade cloth  to cool it off abit .

White is great for overwintering use.
White lowers transmission of light
and thus heat buildup during those warm and bright winter days,
helps prevent the trees from budding out too soon.

White generally has a transmission value of 50% or less,
clear green house films are in the 85%+ range.

Rule of thumb,
reduce light transmission by 1%
it reduces plant growth by 1%

So you can reduce heat by limiting the light and plant growth with white plastic,
or  use clear plastic and ventilation to deal with the heat.

You don't want the white poly film for summer use that is about 55% light transmission vs 91% claimed for clear and IR 6mil poly.

A good example of what is available are the dynaglass corrugated polycarbonate from the Greenhouse Megastore.

Clear is 92% transmission and 1% diffusion
Solarsoft 90 is 90% transmission and 40% diffusion
Solarsoft 85 is 85% transmission and 100% diffusion
Opal = white is 42% transmission and 100% diffusion

http://www.greenhousemegastore.com/product/solarsoft-90-corrugated-polycarbonate/plastic-sheets

My experience is that all claimed transmission values are too high according to my light meter. But 80-90% transmission and 40-100% diffusion defines a good covering for figs IME.

For corrugated I'd chose Solarsoft 85 if single layer and Solarsoft 90 if double layer.

More great info. Are the corrugated solarsoft panels superior to the ones sold at lowes/homedepot? They sell ones that are 90%. The crating and shipping from greenhouse megastore will far exceed the cost of the panels themselves.

Tony:

I don't know how Lowes panels would compare to others. But if both are polycarbonate they're probably similar. There are other ways to get diffusion if you can only find clear panels locally. I've put a single layer of the Agribon 19 inside my clear. This drops the light and heat slightly while adding diffusion. I tried two layers and thought that a bit much. It probably won't be because I'm a bit of a freak about providing adequate light.

Hershall thanks for the offer someone gave me some plexiglass sheets that had the paper stuck to them I spent all day with a power washer the paper came off but the glue wouldn't I couldn't even sand it off which is what I did with the Amber and Red it gives it a nice frosted finish "the search continues" Hershall keep the secret about the JT's between me and you LOL

Tony V I think that the white corrugated roof  is perfect I have a couple of friends that have greenhouses which have a clear material and it was way too hot so they had to end up buying shade cloth I killed 2 birds with 1 stone with the white Last year was my first time using this greenhouse to store my trees this is what they look like in March I had roughly a 3 month jump start "it doesn't get any better than that" 

Dave brings up a good point about the tradeoffs between light, heat, and cooling options in a greenhouse/hightunnel. If a greenhouse isn't equipped with active cooling then one may have to compromise light levels in order to reduce over heating. Tony doesn't say how he plans to cool his structure or I missed it. But that affects covering choices to a large degree.

My greenhouse has full out evaporative cooling and large exhaust fans so I can allow high light levels and associated heat. For a structure like Dave's one has to dial back the light to avoid over heating.

You guys all bring up good points. And I'm totally impressed by Dave's greenhouse. I never imagined it would give you such a jump on the season.

For cooling I was going to be rather simple. I was going to put 2 hinged openings - one on each side by the ridge board. One to blow out hot air. The other to suck in cool air. But maybe I need to think about that more.

Thanks

Growers solution on ebay sells 6 mill greenhouse plastics that is garenteed for four years. have had mine for three with no issues and enough left to re-plastic it again if it peters out. might be something to look into, cheeper than pannels and easy to install.

I thought I posted this already. But it's not showing up. So here I go again. What about plexiglass? Somebody selling 4x8 sheets on craigslist for cheap. Herscell maybe you know since you're in the business. If it transmits to much light I just saw in growers supply you can get a sun shade for cheap?

Last question. Anyone ever use Solexx? Seems to have similiar properties to solarsoft but comes in a roll. So no crating fee and has free shipping through wayfair.