HFGH Polycarbonate Panels Failing (Part 2)

11 years ago

This thread is a continuation of Laserfans thread (HFGH Polycarb Panels Failing!) Click here to see the first thread.

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 canÂt 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.)

IÂll try to look into the UV clear formula of Plasti-Dip next.


Comments (38)

  • laserfan

    >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 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.

  • laserfan

    The panels from Charley's are high quality from Palram--they come with a blue film covering the UV side ("This side up" clearly marked). The coloration is what I would call "frosty" i.e. not white, but not see-thru either. Our GIC (Gardener-in-Chief) declared them "pretty"!

    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).

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  • mudhouse_gw

    Thanks for the manufacturer name on those panels, Laserfan. Glad they look good!

    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 dont 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 its 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 Ive found to dateif 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, Ill 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.

    Ive 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 Ive contacted on this quest, who never reply at all.

    Has anyone had experience with Top Secret Coatings?

  • gardenerwantabe

    SHERI could you use this stuff.
    I don't have the UV problem but if I did I would look for more insulation while adding UV protection because our winter heating cost is our biggest expense

  • gardenerwantabe

    Here is another option and it is cheap

  • mudhouse_gw

    Gardenerwantabe, thanks! Ive thought about increasing the roof insulation too (like Laserfan, choosing 6mm replacement panels, instead of 4mm.)

    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.) Id 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, Id 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 ;-)

  • laserfan

    Well, I haven't seen the PlastiDip other than a spray can at Lowe's (Black!!!) but I have a REALLY hard time imagining that you'd need 5 gallons!!!??? My SnowRoof temporary coating took less than a quart! I just did half our roof, but still... I'd be inclined Sheri to get a gallon of the PlastiDip and try it, maybe just on the "sunniest side" of your roof, though of course that's easy for ME to say! ;-)

    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?

  • mudhouse_gw

    I'd rather keep the shadecloth inside too (GH is in full view of lotsa neighbors) and no wind trouble. First I'm going to try a clear coating, to see if I can stop the yellowing before it progresses to holes and brittleness. I think ALL my walls/roof/door panels are yellowing slightly, so I'm looking for a clear coating I can apply to ALL the outside surfaces.

    Ive 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. Well 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!

  • jbest123

    I wonder if yellow blotching or streaking would occur in time with a DIY UV coating product. Im sure there would be some variation in thickness of the coating. It may degrade the aesthetics of the GH. I will let the original panels go until replacement is required and then consider replacing them with Plexiglas sheets. It would increase my heating and your cooling problem but that may be easier to address.


  • laserfan

    Well, I don't think interior shade cloth works; it sorta traps the heat. I do agree that PlastiDip will likely have Some visual impact--whether immediate or longer-term remains to be seen since no one here has tried it. But in any case I wouldn't consider it a long-term solution.

    >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.

  • mudhouse_gw

    Ive read mixed opinions about shadecloth inside. I have greenhouse friends using shadecloth on the inside, and our temps dropped nicely we added ours (inside) 6 months ago. I can always change it, but so far, the heats been OK (keeping interior temps to within 8-10° of outdoor temps.) I did goof on the density (40%, duh) and Im getting too much light on my plants this time of year. Instead of replacing the inside drape with a higher density for summer, Chief Engineer says we can fasten a second higher density Aluminet piece to the outside roof for summer. Stay tuned...

    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 expectationseach 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 describeI 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."

    Ive ordered the Top Secret Coatings product. Im 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 Ill be replacing them in 6-12 months anyway. I decided to test itmaybe well learn something.

    I emailed Harbor Freight today, and asked: "Do the replacement panels youre 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 wont pursue any replacement panels from Harbor Freightthey would not last any longer than my first set. No telling when theyd 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 Ill also look at better products for the roof (like Laserfans.) Everyones different, but when the roof fails, Ill 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. Im still happy with the rest of the greenhouse, and Id rather just get it done.

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

  • solar_gh


    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.


  • mudhouse_gw

    Thanks Ron! Im not yet convinced I need an evaporative cooler for my collection of tough cacti (110° is no problem for them) and I think I have a good air exchange rate...but Id really like to understand the benefits of a solar pool cover year round in hot climates (touches on Gardenerwantabe's suggestion of UV bubblewrap above.)

    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! :-)

  • JamesY40

    I just saw this discussion and ahte to hear others are having the same problem I have. Early this Spring, I noticed numerous small holes on the south facing roof. I have not had holes on any other panels. Also, the panels on the south roof were brittle. Consequently, a hail storm has come through and dmaged the greenhouse to the point it will have to be relpaced. I was thinking about buying a new HFGH since I still have many parts from my first, but I'm not sure that's the right approach. I'm not sure as to buy another one hoping the problem was an isolated problem or go with another mfg. James

  • mudhouse_gw

    Hello James, glad to have your input to this thread. I don't think anyone knows if this is an isolated problem, but I personally suspect that the HFGH panels don't have any UV coating (again, just my opinion at this point) and that folks in warm climates will probably have problems sooner than folks in other parts of the country. I base this on the discussion we had in the original thread about this topic, and Harbor Freight's emails to me.

    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?

  • troykd

    I think $100 worth of shade cloth will solve the problem. I haven't had any detioration on my panels. I have a shade cloth on through most of the year.

  • tailwheel

    polycarbonate is probably the most expensive plastic made today that is for everyday use. Has anyone here looked into sourcing clear CAB panels? Excellent impact strength, UV resistant and I'm sure that it's cheaper than polycarbonate.

    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.

    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.

  • aircraft_engineer

    replacing/repairing panels - go get either gorilla glue or foaming gap filler (in those "foam in place" cans you get from Home Depot or Lowe's) The glue (or foam used as a glue) will secure the patch (some kind of plastic strip) to the panel. Remember, the foam or the glue is NOT UV proof and WILL yellow as it absorbs UV - but it IS stout to hold the pieces together. (Clamp it to make sure it "fits" after gluing - see below)

    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.

  • weis2741

    I used a window screen I found at lowes it is for the smallest insects and its almost a perfect 60% shade I used it on the south and west sides of the greenhouse looks nice ad keeps sun off my orchids. When I built the greenhouse this summer I bought polycarbonate roof panels from Charlies that have UV protcetion built in they are great. I used the 2'X6 ft ones in the roof. You can see it at in the section called my Orchids it is the last picture on that page.

  • rtyu

    See my post on part 1 of this topic(link below). 6000' elevation near Denver high uvs, 3 years now and no yellowing or holes $80 fix including shipping. I also think the stuff helps strengthen the panels, we have at least 1 hail storm every summer 1' size last June 6th and no damage. It is a transparent clear finish....some one else suggested this stuff years ago, I don't know if anyone else has tried it yet, but mine have held up 3 summers now with absolutely no fading, cracking or pin holes. I can easily see it lasting10 more years if not more, Its called 'top secret coating' it is used to protect war ships from the weather, sun, salt, with the thinner you can apply 3 coats to the outside of the panels, apply it to your panels right after removing their protective film so you can be sure you have a clean surface.

  • mudhouse_gw

    Hello rtyu, and thanks so much for posting here. That's really encouraging!

    I also applied a Top Secret clear coating to my new roof panels, a little over two years ago. The product I ordered was TS-100 One Part Epoxy Marine Coating, with the suggested thinner. So far I don't have any deterioration, but the roof panels are also under 60% Aluminet shadecloth year they do have some protection from our brutal sun. I figured I'd need to give it another year or so before I knew if the coating was really working. So, I'm happy you started your test of the product a year before I did, that's great feedback!

    I only applied two coats with a fine nap roller. Should have applied you did...because I have quite a bit left over. Next spring I need to replace the wall panels, and before I install them, I will be using more of the same product.

    I think my cost was around $100 or so for the gallon of coating, the quart of thinner, and shipping, several years ago.

    Thanks so much for posting and sharing your results. I will also post this same reply to the other (Part One) of this thread, in case folks pull these threads up in the future.

  • rtyu

    Hey mudhouse thanks for your blog it provided invaluable info when I was researching the project 4 yrs ago! The first summer no shade cloth was used, but the heat became intolerable.

    The past 2 summers I have used a 70% light transmission shade cloth, I think it is nylon. The shade cloth is typically hung the last week of May to the last week of about 5 months of the year for the past 2 years. The shade cloth only covers the top and south wall. The east and west sides have been totally exposed for the past 3 years, the coating has not chipped, cracked, peeled or faded.

    Right after I bought the HFGH kit and removed one side of the protective film I spread the panels out on cardboard in my garage, using a fine nap roller and started applying the stuff. The first coat seemed like it was softening the panels almost like they started to melt a little, however it seams like it was just forming a chemical bond to the polycarb as it firmed up well when dry.

  • mudhouse_gw

    I'll admit I was a bit worried when I rolled the coating on my new panels too, but it seems to work fine. I noticed a very slight yellow cast, only barely noticeable, as I rolled on the coats. Seems to dry into a nice tough clear coating, as you said.

    I've been happy to see that none of my coated panels have shown any peeling or chipping either.

    I'm so pleased to know that some of your panels treated with the Top Secret brand product have been totally exposed. That's the kind of test we need, and three years of exposure to sun with no problems is very good news!

    For others reading this thread, here is a link to the Top Secrets website where I bought the TS-100 clear epoxy coating, and TS-101 thinner:
    Top Secret Coatings website

    My original Harbor Freight roof panels were yellow, brittle, and full of small holes after roughly three and a half years (even under year round shadecloth.) I don't think they would have lasted through a hail storm in their fragile state, and I breathed a sigh of relief when we finished installing the replacement roof panels over two years ago.

    It will be interesting to see how many years I get out of this second set of Harbor Freight roof panels, with the coating. Your info has me very encouraged. Thanks again!

  • CanadianLori

    I made a shade cloth out of landscape cloth. Then put grommets in the corners, ran a cord through to help raising and lowering.

    It worked well last summer to control the heat on 100F days.

    I could feel the difference just stepping inside.

  • Textea

    Mudhouse, I know you have the 10 x 12 HFGH did you use a whole gallon of this product on it? I have the 6 X 8 a few months old and live about 50 miles down stream from you and know about the heat and sun in this area. Also did you have to use the thinner? Thanks James

  • mudhouse_gw

    Textea, I only treated the roof, two years ago, as that was the only part we replaced at the time. Now I'm ready to replace the wall panels, due to deterioration (they lasted a bit longer than my roof.) I think I will have enough left of the original gallon to do so.

    I'm thinking rtyu has the 10x12 but not sure. Sounds like he or she used one gallon to do all the panels, three coats. (Maybe rtyu will pop in here to verify.)

    I did use the thinner because the application directions on the website made it sound pretty necessary to thin the TS-100 clear epoxy product. I bought the TS-101 thinner.

    The directions state that it's designed to go on thinner than regular paint (in multiple coats to reach the desired thickness.) Also they warned that if applied too thickly, the result might be extended dry or cure times, or a failed application. "Dilution is required in virtually all applications. Use only recommended thinners. Do not substitute."

    Here's a link to the instructions on their site:
    Top Secret Coatings TS-100 One Part Epoxy

    If you live close to me (with our tough climate!) I think it might be a pretty good investment, although I still wish the Harbor Freight panels didn't require us to take this step.

    I think folks in other climates may have fewer problems, but I've sure learned that the HFGH panels don't have enough UV protection to last many years where we live. One of the first people in this forum to report complete roof panel deterioration was in southern Texas.

    CanadianLori, yup, my plants and I couldn't survive without some kind of shadecloth!

  • Textea

    Thanks Mudhouse, yep I am 18 miles east of El Paso, but before long it will all be connected. Best of holidays to you

  • mudhouse_gw

    Well, we are practically next door neighbors. If you get any extra rain, send it our way. Happy holidays to you too!

  • rtyu

    Yes I have the hfgh 10x12' using the 1 gallon and recommended amount of thinner 3 coats were applied to all panels (still have a very small amount of the coating left though) it was close, the type of roller and your technique may change the results slightly.
    (ie. how much you put on with each layer)

    My only suggestion would be to put two coats on all panels, then when you are finishing the 3rd coat save the 6 panels you plane to use for the north wall for last (in case you run short) Even if you only get 2 coats on the north WALL panels they should be fine, but there should be enough for 3 coats on the outside of each panel.

  • steve333_gw

    I'm just curious, if the HF twinwall panels deteriorated so quickly the first time, why would you get the same again to replace them? Are they really that much less costly than high quality twinwall from Charlie's or a local GH supply place?

    My local GH supplier carries Palram sheets, which run about $2/sq ft in the 8mm thickness. They are easy to cut with most types of power saws and the right blade. I've never checked, but 6mm and 4mm thickness sheets should be less expensive.

    Have to admit, I have never owned or even seen a HF model, but it seems to me that going with a higher quality panel would be the better route to take.

  • mudhouse_gw

    Hi steve333, good question. I always said I'd never buy HF panels again, but when I was faced with the purchase, I caved! It was a combination of price, and convenience.

    At the time, I priced 4mm twinwall polycarbonate at a number of greenhouse supply companies. The best price at the time was through FarmTek (cheaper than Charlie's or any other source I tried.) Their product had a ten year warranty, and was truly UV-protected.

    However, the cost to purchase enough material (just for the roof) with crating and shipping fees to my address, was $410. The cost to order more Harbor Freight roof panels, with shipping, was $135. That difference was enough to give me pause. Hmmmm.

    Note, it's possible folks living closer to urban areas with more businesses would have found better deals on shipping, but down here in southern NM, the only things close to us are lizards and cactus.

    Also, the HF panels arrive sized to fit; if you buy better polycarbonate from a greenhouse supply company, you'll have to cut the material to size yourself for each part. Not difficult, but it does take time, so I factored the convenience in as well.

    Also, occasionally I consider upgrading to a larger home-built greenhouse, so kicking the can down the road doesn't bother me as much as it would if I was positive I wanted to keep this small greenhouse another ten years.

    I think an argument could be made for both sides. If rtyu's and my experimentation with the Top Secrets clear epoxy product pans out, though, it will definitely tip the scales towards using the (clearly lower quality) HF panels and protecting them with the coating, especially if folks can apply it to their new greenhouses, and avoid the need for panel replacements.

    Fingers crossed.

    I think much of the appeal of the Harbor Freight greenhouses is cost/value. They appeal to folks who want to try greenhousing but don't want to make a major investment. I haven't tallied it up exactly for a while, but scrounging supplies, materials, and labor, I figure we have around $2500 in ours total, including kit, benches, sink, plumbing, electric, heaters, thermostats, shadecloth, pavers, and the new roof panels. Over six years that's roughly $400 a year (not including heating costs, which aren't too bad in my climate.)

    So I think many folks who are attracted to the HF structures also enjoy keeping costs low. It's just one option in the world of greenhouses, and not the right fit for everyone.

    Happy New Year!

  • sierrajim

    Hi Sheri / mudhouse -

    We are prepping (laying down 4x6's for foundation atm) to install a 10x12 HFGH, around 2200' in Sierra foothills of California (Nevada City).

    In applying the TS-100, did you prep your new roof panels by sanding them

    to roughen the panel surface a bit for better adhesion? or just peel off the

    film, thin the TS-100 and roll on? Can't use their primer, since it is colored.

    Thank-you for your ongoing support and huge contributions to this site for all of us HFGH builders!!

  • mudhouse

    Hi Jim,
    No, I didn't abrade the surface of the new panels at all, and
    I didn't have any problems with the TS-100 product adhering directly to
    the surface of the panels. No peeling, no flaking, no yellowing from
    the application (well, perhaps a very barely noticeable tint, afterward,
    but nothing that worried me.)

    As you said, I removed the
    protective film, thinned the product with their proprietary thinner, and
    rolled on two coats, letting them dry well in between. (I think rtyu applied three
    coats.) Personally I wouldn't do anything to rough up the
    Harbor Freight panels, since (for me) they have already proven to be
    pretty questionable in their durability, over time. I'd be kind to them!

    do think the TS-100 product helped us a bit, but I'm sorry to report
    that I still only got a bit more than four years out of my second set
    of Harbor Freight roof panels, even with Aluminet shadecloth on top year our tough desert climate. I believe they were getting
    brittle, and a recent hail storm with 1" hail punctured them nicely
    (although the greenhouse frame was just fine.) So we've just covered the
    damaged greenhouse roof with 6ml UV greenhouse plastic, to get us
    through the winter. I

    In the spring, I'll bite the bullet, and order new 4mm twinwall
    polycarbonate, probably from Farmtek, to put a new roof on the
    greenhouse. Their polycarbonate has a 10 year warranty...and UV
    protection. I'm getting too old to keep re-roofing the greenhouse every four years, lol.

    I do think people in kinder climates with less
    intense sun fare better with these HF panels, and I still think the
    TS-100 probably helps extend the lifespan, somewhat. If I was ordering
    new HF panels, I'd use the TS-100 again.

    Good luck with your build!

  • waterstar


    Mudhouse tells me that the TS-100 failed. Of course, I did not read this until after I applied it! DUH.

    Has anyone had success with anything? I most likely won't do mine until fall. I did find some folks cover Covering the questionable polycarbonate panels with high quality UV protected 6 mil plastic film. Has anyone tried this?

    I found it on

    Also, mudhouse, what do you think of any or all improvements mentioned? I really respect what you have done. ( :

  • mudhouse

    Hiya Waterstar!

    Well, I didn't say the TS-100 failed; I do think it did help delay the deterioration from the sun, in my case, and helped the panels to last longer than they might have without it. But I surely do agree, in my case, it did not extend the life of the Harbor Freight panels to anything approaching the 10 year warranty of most quality (non-Harbor Freight) poly panels.

    I don't know how to accurately estimate the benefit for my greenhouse...applying the TS-100 product may have added an extra couple years for my roof panels, in my very sunny climate? I would expect it might help others even more, in less extreme climates than mine. I still doubt it will extend the HF panel life to the same roughly ten year period guaranteed by most (expensive) true UV protected polycarbonate sold by greenhouse supply companies.

    I have some of the 6 mil plastic film on my greenhouse roof right now. We applied it on top of the HF panels, to get us through the winter, after an October hail storm poked holes in the brittle and yellowed roof panels. My 6 mil film was rated to last 4 years, so I would not expect it to last much longer...but, maybe, in some orientations, and some climates? Others might have a better guess.

    Yes, the blog you linked to above is super! Dewey302 posted in this forum a while back, too. I just reread the recent comments in his blog, and 8 months ago he posted that his 6 mil UV film had been in place for over three years...and that his panels still looked like new. Even on the sides of his greenhouse not covered with shadecloth. His most recent posts don't mention any deterioration of the film itself, so maybe it could last longer than 4 years.

    So, the additional layer of 6 mil UV greenhouse film might be the longest lived solution so far, in the ongoing search for ways to help the HF panels last longer. I hate to make declarative statements, because every so often people will post here saying that their problems with the HF panels are less severe than mine have been. I think our experiences all vary, because our climates all vary.

    I think Dewey's ideas and approaches to improving the Harbor Freight kit are all excellent, and his blog is super helpful.

  • waterstar

    Thanks mudhouse. Now I will read Dewey's and yours and try to combine them. I probably won't have time until Oct. or so (if then) to do this part of my project. I am still working on the SCHS heat sink. ( :

  • cassiesey

    I live in Oregon and this is my third summer with the HF greenhouse. Last Spring we noticed the pits, which on closer inspection were holes ( so we had only two mild winters with it). I believe the holes are on all panels except the door and side opposite (would have to go out in 90+ degrees to check - ain't going to happen; the panels face E andW ). We thought it could be from our neighbors' firepit fires, but the plant life and wooden fence don't show it. We are thinking of trying to cover it with heavy visqueen. The two vents, which get opened occasionally in the winter, would be the biggest problem. We are two retirees that can't crawl up and down like we used to do and cost is a consideration, too. I was wondering - would clear caulk smeared over the holes work? Thanks for this thread. We thought we were the only ones with the pitting / holes problem.

  • mudhouse

    Hi cassiesey, sorry to hear you've had the same problem.

    The holes in my Harbor Freight polycarbonate have appeared in only the outer wall of the twinwall poly. I haven't used caulk, but I think it would work, to help preserve the insulating quality (and and to help keep water out of the little channels.)

    I had some clear duct tape on hand, so I cut little squares about 1" by 1" and stuck them over each hole. That worked too, although it looks a little silly (up close.) But they've stuck on for years, and it solved the problem...or, at least, kicked the can further down the road.

    I'm not familiar with the UV protection of the heavy visqueen you mentioned; the UV protection would be my only concern. Some clear plastic sheeting not designed for exposure to the sun can deteriorate quickly. We bought some of this 6 ml greenhouse quality polyethylene film to cover the roof last fall (we placed it on top of the damaged roof panels, and it's still in place.) It's rated to last 4 years, although I hope to get the time/courage/energy to replace our roof panels before winter.
    6 mil greenhouse polyethylene film

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