Solar Pool Cover - Bubbles In or Out

17 years ago

Hi,

I pust a solar pool cover on the inside of my greenhouse but it really doesn't seem to be making that much of a difference. It reaches about 3/4 of the way down to the ground, which may be an issue - I bought a 20' x 40' which isn't quite big enough ! The other thing is that I installed it bubbles facing out towards the g/h plastic. I wondered if this may be an issue as they wont be trapping warm air and insulating.

Does anyone have any ideas on this ?

cheers

Simon

Sort by:Oldest

Comments (3)

blondboy47
17 years ago
I can help on that one.

I did some experiments using bubble wrap (same as pool cover, just different sized bubbles; concept is same).

The insulating factor works better with bubbles towards the INSIDE. One reason, is that not only do the bubble help to retain the heat, but the solid backing, which is facing out, helps to put a barrier between the inside and outside and stops cold air flow.

But, it's very important, for the cover to work is to have it "sealed" at all edges. If, for example, if it's only 3/4 the way down and air can get up between the cover and the outer shell of your greenhouse, then you have cold air circulation which will basically thwart any efficiency that the pool cover should provide.

So, if you don't have enough pool cover, then perhaps "seal" any open areas with regular bubble wrap or even double-layered plastic (not as efficient, but better than nothing).

Also, you may find that 1 sheet of this pool cover, while (when sealed up) will help, it may not make a huge difference in a zone 5 if you are heating it with some heat source.

Over the last 4 years, we have done some experiments with layers.

In all experiments, the bubble wrap is sandwiched between 2 layers of poly plastic that covers the greenhouse. To be clear, 6 mil plastic on outside of greenhouse, layers of bubble wrap, then another poly plastic sheet on the inside of the greenhouse. This way, the bubble wrap is between the outer and inner plastic sheets. The 2 layers of poly plastic, outside and inside are sealed up completely around all edges using a zippering system on the frame of the greenhouse (wire lock I think itÂs called)
We have found this to provide the best "R" value and heat retention.

Here are our results.
NOTE, ALL BUBBLES TOWARDS INSIDE OF GREENHOUSE (

BEST insulating factor, good light penetration: The 1st winter, we had 3 layers of bubble wrap.

GOOD insulating factor, POOR light penetration: The 2nd winter, we tried 5 layers.

WORST insulating factor, excellent light penetration: This winter, we tried only 2 layers.
We find that during the day, the greenhouse heats up nicely with the SUN, best of all other experiments. HOWEVER, with sun gone, it loses the heat faster than the other 2 methods and will cost more to heat during cold snaps.

We will be going back to 3 layers next winter. OR, we might decide to change from bubble wrap to 3 sheets of pool cover, where each is cut as 1 large sheet.

Hope that helps.
nathanhurst
17 years ago
Just to note, blondboy didn't seem to have read your post carefully, yes, you want the bubbles facing outwards when installed on the inside of your greenhouse, because you'll get an extra layer of air trapped between the bubbles. The bit about sealing around the edges is good advice.
Related Discussions
Does bubble wrap / pool cover block sunlight?
Q
Comments (11)
themaniam1 Actually, that's exactly how our GH is set up. Double poly inflated with 3 layers of 1/2" bubble wrap sandwiched between the poly. Works a treat. Sure, there's some light loss, but like wyndyacre stated, the tradeoff is worth it. We are able to keep the GH nice and toasty on the coldest nights and as for light, well, the plants sure don't seem to mind a little light loss. The banana trees are growing, the palms putting on new fronds, plants are flowering, etc. But, only for simplicity, I think we're going to the clear pool covers for next year. A local supplier can supply 12'X24' sheets for only $55 CAN$ and the plastic they use is 11 mil. We'll either buy 2 sheets or perhaps 3, depending on light loss and insulating value. We tried 5 layers last year, but there was too much light loss, to the point where the GH wouldn't heat up during the day very much. We had 3 the year before and have gone back to 3 this year. It's working out well.
...See More
Solar pool cover year round in hot climate?
Q
Comments (19)
My goodness, this thread takes me back in time! Mighty_turf, I ended up not using a solar cover on my 10x12 HFGH (decided my climate really didn't require it) so I am no help on best places to purchase. I believe conventional wisdom is that most heat loss in a greenhouse occurs through the roof. If I were to purchase one I'd definitely cover the roof, and probably lap it down the sides a bit, depending on the size I ended up ordering. Hopefully others here will have more specifics for you. If not, I'd consider starting a new thread with your specific questions about solar pool covers, to get a few more eyeballs on your questions. (Sometimes newer threads get more attention...?) Happy New Year!
...See More
Solar Pool Cover - Keeping from flying off
Q
Comments (38)
karenrei, I don't have a hoophouse, each wall and the roof are totally seperate segments as to R value, covering etc. stressbaby nailed it on the head on this thread http://forums2.gardenweb.com/forums/load/strucs/msg0909104730738.html and I am surprised that thread did not get more input. Identify areas where improvement can be made and fix them. Then look at the whole structure again and work out where the "new hole" is. On the thread about the polystyrene sheets, http://forums2.gardenweb.com/forums/load/strucs/msg081128491250.html I tried to point out that adding an R3 insulation to one wall was great, bumping it up to R6 may be a waste of money because there may be another place you could put some R3. Yes, In retrospect my south roof (and sorry to use trade names but people can look it up and understand it better) should have been Tufflite IV outer, pool cover and then Tufflite infrared on the inside. A nice sandwich and cheaper and easier to install then polycarbonate triple wall. Yes I know polycarbonate triple wall will last longer but, it is also very expensive. I had a standard double poly inflated south roof so I gained some insulation advantage but all of that insulation was lost by a breach of the outer layer. (see my rant on this thread) http://forums2.gardenweb.com/forums/load/strucs/msg0409365924489.html OK, so I know I am going to lose light on the south roof because of this sandwich but I am going to get a boost in insulation, and because of the bubble wrap sandwich I am also going to get some protection from damage. The sections would be 2ft by 8ft and if I had a breach of the outer skin then my south roof loses 1/12 of its R value not 100%. Next, as in reducing light transmission, as you say most of the light in spring is through the south wall, so a reduction in light transmission in early spring of say 15% from the south roof is still a loss but a small loss as not much of the total is coming in that way. ""any areas that don't get much sunlight being as heavily insulated as you can with opaque (preferably reflective, in my opinion) insulation."" North wall is solid and painted white inside (reflective). Half the north roof is solid. Changes to my configuration next spring? 1, Shade cloth hung vertically inside about a foot from the south side to reduce the tendency of young plants to grow towards the south side but as the shade cloth is on the inside it will block light to the plants but still contribute to raising the air temperature in the greenhouse. 2, Wait until the corn and bean crop is harvested and there is snow on the ground and then set fire to my old barn to the south where the shingles that hit my greenhouse in high winds come from. (insurance company please note, that was a light hearted attempt at humour.) Umm... on second thoughts, I will insure my greenhouse! :)
...See More
Solar Cover-Which Side Out?
Q
Comments (2)
Thanks much Zubababy that makes sense. No snow here in desert... but occasional rain and lots of dust to get trapped in between the bubbles. Patiofarmer
...See More
gardenerwantabe
17 years ago
Posted by nathanhurst VIC Aust
yes, you want the bubbles facing outwards when installed on the inside of your greenhouse, because you'll get an extra layer of air trapped between the bubbles. The bit about sealing around the edges is good advice.

Nathanhurst it correct the air space will give you added insulation because it is the air gap that slows convection.

Solar Pool Cover - Bubbles In or Out

Comments (3)

blondboy47

nathanhurst

Related Discussions

gardenerwantabe

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US