My understanding is that the higher the number, the more insulated the greenhouse is for growing plants in the winter months. If folks don't plan to grow anything in the coldest months where temps dips down to 0 degree F, would this really make a difference in their choice of which greenhouse is more suitable if all other construction, set-up,wind, snow load and warranty factors were equal?

Julia

Are you going to use the greenhouse during cool weather where you'd prefer to keep things warmer at night? If so, the thicker panels will help. My take is anytime some nighttime warmth is desired, then more insulation is better. What times of year are you going to be growing things and what are you growing? Do you plan to heat your greenhouse?

Karin

I grow tomatoes,peppers, eggplant, squash, cantaloupe and lots of herbs. I want to add more but no room inside to do all of it and I have no way of knowing if our spring will be so rainy and cold we are delayed planting out. I also am an avid perennial/annual seed starter as well.

I start putting out seedlings mid-April or mid May depending on our anticipated last frost date and the weather.Right now I start all my seeds indoors and then transfer them out to the garden. I'd like to be able to start seeds in the greenhouse but not sure about just how much heat I'll need to achieve this. Newbie to all of this so researching all the issues.

I want to use one side of the greenhouse as a planting bed or make a soil bench to start broccoli, spinach, etc mid season so I have these still growing into late November/early December.

My thoughts were to place the greenhouse in a north - south direction but will be exposed also to east-west as well. Very open area and we do have high winds from time to time. We don't get as much snow as folks in the Buffalo NY or Binghamton/Syracuse area. We are in between those cities here in Upstate NY, but do get a least one to two snow storms were we may end up with 10 inches of snow but because of the winds, we get alot of drifting. Our temps do not get very often get below zero however windchill may feel like below zero.

Julia

You sound like the ideal greenhouse owner to me! I do all of those same things and I get better results with the GH than I ever did indoors. In general you can start things quite early in the GH in springtime. It gets very warm during the daytime, even by March it is toasty in there and with the bright light you get very strong seedlings. Of course it is cooler at night and there are ways to deal with that, such as covering your seedling trays with frost blankets, using a heat mat, bringing seedling trays inside if it's exceptionally cold, or using a heater.

Using today as an example, it's a raw 26 degrees outside and mostly cloudy. Not a nice day. But in the greenhouse it's 58-65, depending on the location, and the lettuces all look pretty happy.

Our GH is oriented north-south, which I really like. That way neither side is shady and it provides maximum growing space. Planting things in the ground is a wonderful means to have a very long growing season. I think you'd be able to get cool weather crops to go all winter long, although they won't put on much new growth in Dec-Jan.

Back to your original question, I'd go with the 8-10 mm panels if you can. Having more insulation is never a bad thing if it is not cost prohibitive.

While you are in the research (aka dreaming) stage of the process, you may want to read The Greenhouse Grower's Companion by Shane Smith, and/or Elliot Coleman's books.

Good luck with your research and planning!

Karin

Advice?

Julia

karin: Those books are on my Amazon Wishlist already. Checking libraries to see if they have them available before I buy my own.

Julia

Back to my original question though, it seems the higher the number the heavier and more efficient the polycarbonate is.
I don't want to spend X amount of dollars and within a year or two, have holes, yellowing and cracking occuring because I choose a 4mm or 6mm versus an 8mm or 10mm. I am in a high wind area so stability is a number 1 issue.

So if anyone has a greenhouse with long term warranty and high polycarbonate rating, I'd appreciate reading your feedback other than a Riga GH.

In the same token, I'd appreciate hearing from anyone who has a shorter term warranty, lower polycarbonate rating, that the GH is still in great shape after several years of use.

Julia

The difference in longevity of panels is not based on the size of the air pockets (4mm,6mm, etc). The quality of the plastic used in the panels and the UV protection is what counts.
So, getting feedback, as you have done, is probably the best method to find a good supplier.

Cost also rises with the thicker twin wall of course, life expectancy 'supposedly' remains the same. Our old greenhouse had 8mm on the roof and after 15 years it was still just fine (until it burned down). We went with 6mm on the new one specifically to increase light transmission because insulation (if needed) is easy to do and is rarely needed in our zone.

Lastly, the multi-channel 10mm and higher just has more channels for moisture to get trapped in and for algae to grow in which is a real pain.

Dave

Julia

"Glad someone finally mentioned light transmission. With the thicker twin-wall you are trading off light transmission for a minimal amount of insulation value."

The specifications I've seen suggest the opposite. Here's some numbers for Green-Tek's twin wall polycarbonate.

With increasing panel thickness there seems to be a minimal loss of light transmission with a more substantial increase in insulation. I use their 8mm triple wall which still has 76% light transmission and an R-factor of 1.99. I don't see how panel thickness would have any impact on lifespan, so I don't think that's a concern. I'd go for thicker panels unless cost becomes an issue.

One more benefit is that thicker panels are stiffer and don't require quite as much framing to support them. And less framing increases your light transmission.

Julia