Well, let me just start by saying that I have been selling and installing polycarbonate sheets since 1993. I see as much confusion in this discussion as there usually is concerning polycarbonate. I will try to make a list of the questions in this thread to keep this simple. 1. The higher the number (thickness) the more insulated the greenhouse is in the winter months. A) The number for the polycarbonate refers to the thickness between the 2 outside sheets. So, the 6mm is 1/4" thick overall and the 16mm is 5/8" thick overall. The R value for 6mm is around 1.6 (depending on the manufacturer of the sheets). The 16mm has an R value of around 2.5. The greenhouse will not maintain its heat overnight. You must supply supplemental heating or use solar practices to keep the greenhouse warm. There will be an energy savings with the higher R values. It will take less energy to heat it. There is a formula to figure out how many BTu's are needed. It is the surface area of the greenhouse x the desired difference in temperature outside and inside x the insulation factor of the covering. 2. Warranties A) Warranties are dependent upon the manufacturer of the sheets. All of the multiwall sheets that I deal with are UV protected. This is what keeps the sheets from breaking down in the sun. Most greenhouse multiwall sheets have a warranty between 10 years (that the light transmission will not vary a set amount) to 20 years. Just check with the manufacturer to get this information. If the sheets are not UV protected don't use them for a greenhouse. 3. Snow load A)The snow load is determined by the frame. The polycarbonate manufacturers have lists showing the required framing to meet certain snow loads for each thickness of polycarbonate. Here is an example of one. See the bottom of page 2. https://advancegreenhouses.com/wp-content/uploads/2014/08/polycarb-installation.pdf If you are buying a kit the manufacturer should be able to tell you if the greenhouse is rated and what psf snow load it is rated for, as they have designed the frame. 4. Weight A)Polycarbonate is a very lightweight material. For example, a 8 x 12 sheets of 8mm will weight approximately 40 pounds. A 8 x 12 sheet of 16mm will weigh about 68 pounds. 5. Light transmission A) The light transmission of 6mm clear is approx 80%. The light transmission of 16mm clear is approx 74%. This is not relevant regarding greenhouse usage. These numbers will vary from manufacturer to manufacturer. It is when you get into the bronze and opals that may have as low as 40% light transmission that you want to stay away from these for greenhouse use. If anyone has another specific question about polycarbonate I would be happy to answer. Tammy, www.advancegreenhouses.com

I was away for a couple of days. #1. Absolutely! You're transferring BTUs from the collector into your pit during the day. It's essential for the operation of the system for the pit to be warmed. If you have direct sunlight, that collector will get hot very quickly. Depending upon the angle of the sun, and hours of light, you should get about 30,000 to 40,000 BTUs per day into the pit. It can hold a lot more than that, but you're limited by the hours per day, and also the relative inefficiencies. If you had a warm spell during the winter where you didn't really need to run it at night, theoretically, you might be able to charge it with maybe a couple hundred thousand BTUs. #2. You should wet the ground thoroughly once you've completed the structure. It should remain sufficiently damp after that point with the factors you mentioned. Make sure you wrap the tarp up and over the foundation such that outside rain won't be able to fill the pit -- otherwise, you'll have a swamp in there! #3. The hinged covers have three purposes: a) reflecting additional solar energy to the collector via the mylar film (make sure they're angled correctly when attaching the chains). b) avoiding snow/ice/freezing at night during the winter. Depending upon your hardiness zone, it may also be necessary to circulate some water through the collector at night to avoid cracking the cement or damage to the water lines. If severe freezing is a sure thing during the winter, then the collector should run day and night. Your "day/night" valve will just open the loop through the radiator, instead of shutting off flow to the collector too. c) to protect the solar collector during the warmer months when the system won't be running. Hope this helps. -Bruce

Just center the panels on the studs and water leakage won't be an issue. Water dampness is a major issue so your wood should be a type that will resist decay or be treated (most common). Otherwise your costly polycarbonate panels will outlast the wood that they are attached to by a factor of 5-10. I believe a rubber washer on each screw is worth the cost and effort in securing the panels and you don't want to indent the panels when tightening. Moderate holes can be filled with "Great Stuff" foaming caulk.

There is also www.FarmTek.com - they have twin-wall panels made by Palram, custom @$5.95 per 4' sheet and 4x8' sheets @ $41.95. Shipping seems to be $7.00 per linear ft per package up to 12' - to a maximum no. of sheets per package of 50. They also have a roll of twin-wall corrugated plastic: 8' wide; each @ $7.39 per linear ft, and a 250' roll @$6.95/linear ft. They don't say what the shipping/freight charges on that would be. You can also call them - 1-800-327-6835. While I am not sure how much they would be price-wise compared to local sources, their prices for the water filters I have bought from them seems to be competitive ($5-7 against what I priced at Lowe's a few years ago at over $15!) - they have stuff for agricultural growing and storage, so they carry everything that can come under that heading - the specialty catalogue I just got, for that only, runs to 352 pages.