Confused about Polycarb

16 years ago

Greetings,

Been doing a lot of research about the best roofing material to use on my GH, which is in mid-contruction. The GH is of collected alum double-glazed windows and for my area, I need a roof that will let in as much light/heat as possible (overheating is not a critical issue), and I've pretty much decided on polycarb panels/sheets. But I'm confused as to the pros/cons between the corrugated polycarb (single thickness), and the twinwall polycarb. I'm sensing that if one chooses the twinwall pc, there are more "accessories" needed for installation than with the corrugated - yes? Is there a general problem with mold buildup in the twinwall tubing?

Here in SW Oregon, we get very dry, but not especially warm summers (avg temps btwn 70-80) with lots of sun - but winter is exact opposite with lots of rain and little sun (avg temps (40-50). So which of the two would best meet the needs under these conditions?

Thanks for your responses.

john

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Comments (7)

lilydude
16 years ago
I just put up a greenhouse in SW Washington state, and used the single-wall polycarb. It's readily available and easy to put up. The double-wall is very hard to find, and is a major science project to put up, because of all the aluminum extrusions. But if you are planning to heat the greenhouse in winter, you should probably use the double-wall, since its thermal resistance is so much higher.
ole_dawg
16 years ago
I am giving serious thought of using a double wall pool cover. Birdwidow mentioned she had one, but so far I have been unable to see it on the net.

1eyedJack and the Dawg
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oakhill (zone 9A, Calif.)
16 years ago
John,
The major difference between polycarb sheets and twin wall panels , besides the cost, is the heat loss factor. Single layer- 1.20, twin wall- 0.65. That means about a 40% savings on winter heating with twin. The light transmission is: single- 87%, twin wall- 82%. The framing for the twin wall can be as simple as a slotted wood frame. My greenhouse uses this technique, works very well and no metal is needed. Mold should not be a problem with the twin wall, if the ends are sealed according to the recommendations.
greenhouser
16 years ago
Why not check out your nearest pool supply Place? They may have just what you need.
tsmith2579
16 years ago
How often will you need to heat? How many nights do you have below freezing? Do you plan to actively grow plants in winter or just warehouse them until the next season? I am just warehousing my plants. In Alabama zone 7b/8a, I have about 30 nights per winter when I need heat. I used single ply corrugated plycarb. My greenhouse is 9'W x 16'L x 8'H with a 9'Wx6'Lx10'H addition. On a 26-28 degree night a 10K BTU heater keeps it above 50 degrees.
drfugawe
Original Author
16 years ago
tsmith,
I think our winter climates are similar - only maybe 10-15 nights of freezing temps. Mostly I want a GH to extend the seasons, warehousing, and getting seedlings started in spring - and if I find that the cost of heating is not prohibitive, then I'll try some winter lettuce/toms, etc. What would you estimate your winter GH heating bills to be?

Thanks all for your replies.
john
tsmith2579
16 years ago
Hi, John. I use K-1 kerosene heaters for heat. I have a primary and a backup heater. If we have a really cold nights I will use both heaters. I keep a log of my heating costs. I've used about 40 gallons of fuel this winter which costs $3.50 per gallon or about $140. There were maybe 10 nights when I used both heaters. I usually have about 30-40 nights when temps dip below 35 degrees. When I first started using kerosene it was 99 cents a gallon. Heating bill for the fiorst season was about $45. How times have changed. A greenhouse is definitely not a poor man's hobby,

Confused about Polycarb

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