I checked into UV blocking window films. The ones sold at our local box stores are made by Gila Film Products. They do have a great range of products, and good support staff. Some of their films block all UV, in either clear or a range of tints, and come in 2'-3' widths. I thought we had a winner!

Unfortunately, their support dept says the films absolutely cannot be adhered to any plastic product, including polycarbonate (the film will turn milky and bubble, and will become embedded into the poly surface itself.)

We could leave the clear backing in place, and find another way to affix the film to the poly panels (use UV resistant rubberized construction tape along the edges?) But, they say the film will only last 2-3 years in exterior applications. (When installed on the interior, as designed, it has a 10 year life span.)

So, $12-$15 per roof panel...reapplied every two years (in my climate) along with the hassle of taking the roof apart...I might be better off to just buy new UV coated panels with a longer lifespan. It's still a possible solution to buy time, and the product would be easy for folks to find (online store at above website, if Lowes or Home Depot doesn't have the product in stock.) I was a bit disappointed in the lifespan of the film, and it doesn't sound easy to install since we can’t use the adhesive backing.

(If anyone tries this themselves, be sure to email the company for advice on which way the film should be applied to the outside of the poly panel (clear backing facing out, or clear backing facing the panel.) I tried to get that straight in two emails, and I'm still not sure I got the right info.)

I’ll try to look into the UV clear formula of Plasti-Dip next.
Sheri

I think the "clear backing" is the "adhesive" side, which is released via water i.e. you wet the glass and the film (after removing the backing) and that side is the side that is supposed to face the sun. So it's meant for inside ONLY, and if you applied it that way (i.e. to the underside of the roof panels) it would only accelerate the self-destruction of the polycarb. And I'd trust the advice that it would NOT adhere to the polycarb--not just that polycarb is not glass, but remember too it is not perfectly flat. I've used that stuff here and while it works well enough for glass, it surely is expensive.

Thanks Sheri for starting the new thread. Wish I could close or lock the old thread but this board doesn't seem to have the usual BBS controls.

I think my Charley's Heat Control panels arrive tomorrow. I'll let you know what they look like asap.

The instructions call for sealing tape Up, and breathable tape Below, and in searching on this found this page which explains all. It seems certain that the breathable tape sold by Charley's is this very Palram product--the pics tend not to lie.

Although I probably will NOT install them until fall at this point (it's already REALLY HOT here!) I can recommend to others who may be in need to get these 2x6 panels while they're on sale (again, $264 shipped for 8 panels).

Okay, more research.

In the earlier thread, cuestaroble was kind enough to track down a polycarbonate supplier, who suggested the Clear UV formula of Plasti-Dip as a way to add UV protection to polycarbonate. The UV formula is only available in 1 or 5 gallons, and can be sprayed or brushed. The main problem is cost. One gallon covers 30 sq feet, so it would take about 5 gallons to cover the roof to the recommended thickness (15 mil, 3 brushed-on coats of 5 mil each.)

$245 (five-gallon bucket of UV clear Plasti-Dip, plus shipping) would cover the roof, but not the walls. It's still less money than all new roof panels, but not inexpensive.

Also, I found a One Coat Clear Epoxy made by Top Secret Coatings. Their rep says it can be applied to polycarbonate, and that it has excellent UV protection and flexibility. They don’t have knowledge of anyone using this specifically on greenhouses. The site says it can be applied to a large range of materials including fiberglass and plastic, and it’s applied by brush, roller, or sprayer. They cite a product lifespan of 8-10 years.

Website description says: "a single component, oxygen cured, self leveling, waterproof coating that produces a film that remains both hard and flexible," and "a low film build, high performance clear coating, fully submersible and without resin color."

They suggest thinning by 15-20% with their TS-101 Thinner to achieve the desired 2 mil coat thickness. The coverage is estimated at 700 square ft/gallon, so one gallon should cover the entire greenhouse, roof and walls.

The One Coat Epoxy is $28 per quart, or $84 per gallon; thinner is $11 per quart. With my shipping, one gallon of finish and one quart of thinner totals $108. This is the least expensive option I’ve found to date…if the product works.

Time to decide about applying a product not specifically tested for greenhouse use (to their knowledge.) Since my panels are already slightly yellow at 7 months, I may not have much to lose. If yellowing indicates future brittleness and holes, I’ll be buying new UV coated panels anyway. I can test for immediate problems on my small scrap of poly, but the only real test would be to apply it to my greenhouse and wait.

I’ve Googled for reviews of Top Secret Coatings products, but found few comments. Some question the "one-coat epoxy" name (true epoxies have two parts.) This company is active on the internet, under various website names, and they also pop up in forums replying that their product is a good fix for the question at hand (a sales technique that makes me nervous.)

However, their response to my questions was prompt and thorough...unlike most companies I’ve contacted on this quest, who never reply at all.

Has anyone had experience with Top Secret Coatings?
Sheri

If UV bubblewrap works somewhat like your exterior pool cover, (and if I'm thinking this through correctly) I don't think I could use UV bubblewrap on my roof exterior year round here. Cooling is always my biggest problem, and my GH gets very warm on sunny winter days as it is...even without nothing on the roof. (I needed my exhaust fan periodically for much of the winter.) I’d be especially afraid to add anything to the roof year round that would hold heat in during summer. But, something like that might be a possibility for folks living in cooler climates like yours...? Maybe I have my thinking backwards on this issue, but that would be my concern in my hot climate...?

I looked at the Shade Sails you linked to. Looks like a good product; fabric is made by Coolaroo, has a 10 year warranty, and blocks up to 50%-90% of UV rays, depending on shade density.

This brings up something I'm wrestling with. Several folks on other other forums have suggested shadecloth as a solution, but I'm thinking it's not enough. Blocking 50% of the light (so I guess 50% of the UV rays) would help, but it's still not like having the UV protection in place on the entire greenhouse, since most of us don't shade all the panels. If I'm only blocking 50% of the UV with shadecloth, doesn't that mean I might get two years from my panels, instead of only one year, like Laserfan? And stubbornly, I’d like to find a way to prevent further deterioration on the unshaded walls as well.

If the Top Secret coating could provide UV protection for all the panels for around $100 (probably too good to be true) then shade cloth anywhere could be an extra benefit. I know I can't shade everything...and what I really want is what Harbor Freight advertises...clear UV protection on all the panels, shaded or not.

Stubborn Sheri ;-)

I have now an Aluminet for summer (not deployed yet) which is not going to cover the entire GH, it's going to get blown-around like heck so it's not going to last forever, and also it's gonna look like cr@p, but that's life in the sunny South I suppose. Clearly I'm not a shadecloth or pool cover or bubble wrap fan, at least not over this UV thing. Yeah I know--who cares about aesthetics; it's all about the PLANTS!

But Sheri your HFGH is IMO a beautiful thing and I'd hate to see you cover it?

I’ve asked Plasti-Dip why their product specs recommend such a heavy coating (three coats, 15 mil total.) They list coverage per gallon as only 30 square feet, but maybe that's not necessary for UV protection only? The other product from Top Secret Coatings only requires a thin 2 mil coating to provide UV protection. We’ll see what they say about this specific application.

I think I found the coating mentioned early in the last thread, that turns white in sunny weather, and clear in rainy weather. Vari-Shade is sold by Charley's Greenhouse, and it can be applied to polycarbonate. Their support said it doesn't block all UV, but since it does block some light when opaque, they guess it might slow deterioration to some degree (same as shadecloth.)

Sounds like an interesting product, but I'm still stuck on finding better UV protection...if possible!

>I will let the original panels go until replacement is required and then consider replacing them with Plexiglas sheets.

That's what I'd do, except: Plexiglass??? No, a better grade of (UV-warranteed) twinwall polycarb of the Solar Heat Control type (like I bought! :D) would be best, at least for rooftops down here in 8b. If I lived Up North (horrors! never again!) I'd consider triple- or even quad-wall polycarb, but not plexiglass.

Plasti Dip says: "Plasti Dip has been used on this application in the past. You would need to try the product to see if it meets your expectations…each gallon covers 30 sq ft at 3 coats, which is 15 mils. You can apply fewer coats, or thin the Plasti Dip down with 10-20% naphtha or toluene paint thinner. The more coats, the better protection, but this is up to you. We usually recommend a good 2-3 coats on any application."

Top Secret One Coat Clear: "Our products are used all the time to refinish and protect a variety of surfaces including the kind of panels you describe…I believe the (Epoxy Clear) is your best bet because it has excellent UV protection and is more flexible… independent accelerated weather test data by Siemens shows the film maintains its integrity more than 40 years in a marine environment, which is astounding performance."

I’ve ordered the Top Secret Coatings product. I’m not worried about the aesthetics of streaks if they do show up. (If stopped the deterioration, streaks would be fine!) But, based on my yellowing 7 month-old panels and our extreme climate, I bet I’ll be replacing them in 6-12 months anyway. I decided to test it…maybe we’ll learn something.

I emailed Harbor Freight today, and asked: "Do the replacement panels you’re currently shipping have the same amount of UV protection as the panels that were shipped with my greenhouse kit?" Their reply was "Yes they do."

So, in my climate, I won’t pursue any replacement panels from Harbor Freight…they would not last any longer than my first set. No telling when they’d ship, anyway.

I'm considering eventually replacing all the panels with UV coated polycarbonate. I could replace the entire glazing (roof, walls doors) with Farmtek 4mm UV coated twinwall poly for (roughly) $860 with shipping/crating, but I’ll also look at better products for the roof (like Laserfan’s.) Everyone’s different, but when the roof fails, I’ll probably replace all of the panels, just so I can focus back on my plants. I doubt my south and west walls (and west doors) will last much longer than my roof. I’m still happy with the rest of the greenhouse, and I’d rather just get it done.

Meanwhile, I’ll see how this clear one-coat UV product goes on; for the cost, I think it’s worth a try. If my panels have no UV coating (that’s what I think) then my climate is going to cause their failure anyway. It’s just a matter of when, and I predict mine will fail sooner than most. After I’ve coated the panels with the Top Secret Coatings product, I’ll take more pics in the sunny months ahead to monitor the progression of the yellowing.
Sheri

I think your reasoning about using outside shade and bubble wrap may be incorrect. As the sun's rays are slowed by material such as glass or similar the light is slowed and turned to heat depending on the material of course. Here in the Phx area I have a pool cover, 50% green cloth and 22% white cloth all on at the same time. I still get too much light for some tropicals and house plants. I have 2 fans close to the peak that point towards vents in the front above the doors for some temperature modification and air movement. I also run a mastercool wall cooler on a t-stat and misters that come on several times in the daytime. When we had a recent 110 degree day my high is the gh was 83. This is due to residual moisture from the misters evaporating as well as the cooler running about 40 minutes of every hour or so. Since I have a solar panel minifarm (500 watts) on the patio roof and a control and charging system, all my electrical costs were up front so to speak. I think the secret to temp control is in air exchange and cooling by evaporation (7% humidity today). I know this doesn't work for everybody for various reasons but the principles are the same, shade, airflo, moisture evaporation and proper ventilation.

Ron

I worried about pulling this thread away from the topic of HFGH poly panels, so I started a new thread to display my confusion, here:
Solar pool cover year round in hot climate?
If you have time to visit that thread, I'd sure appreciate your thoughts! :-)
Sheri

HFGH tells me the panels they're replacing (on a case by case basis) have the same amount of UV protection as the ones that came with our kits. I take that to mean, no improvements have been made. So, my guess would be, if your first HFGH had deterioration problems in your climate, the next one would too, eventually. That may be a more pessimistic outlook than some folks would have, and no one really knows...but that would be my own guess.

Was your frame too badly damaged in the hail storm to look for replacement panels from another supplier? I was recently in touch with Charleys Greenhouse Supply, and they told me they would be willing to special order 4mm twinwall polycarbonate panels (they usually don't stock it.) Also, Farmtek sells 4mm panels. None of it is cheap, but would probably be cheaper than buying a whole new greenhouse frame...if you can salvage yours?
Sheri

Here's a place that I found that gives some specs. No connection to me, just a thought for the rest of the people here. http://www.k-mac-plastics.net/cellulose-acetate-sheet.htm

I was going to take advantage of the 15% offer I got in the mail from HF until I ran into this thread. I'm not so sure now, cuz I'm in sunny Californias San Gabriel valley where it's hot and plenty of sunshine. From what I've gathered here, the polycarb panels would'nt last 5 minutes.

My thoughts have turned to designing a GH using steel studs available from Lowes or HD. I'm sure I could build something competetive with HFs offerings.

To do it right you need to cover both up and down sides. about 2 inch width will make it a strong enough to hold. If it's not a straight break, zig-zag it to make it fit.

if you want to replace a broken panel with a thicker panel you can use a router to remove the edge you don't want and then glue on a filler piece to make up the 4mm thickness. you WILL need to use a couple of wood pieces and clamps to hold the filler in place while the glue sets. Epoxy also works well in that type of application.

I've got a request in to a coating manufacturer for a clear UV coating that can be sprayed with an air spray gun.