Condensation in twinwall polycarbonate channels

 I, a rank amateur and non-handy person, am trying to restore an old GH
with aluminum frame. I replaced the glass with twinwall polycarbonate
sheets. The frame has a groove in the bottom where the glass used to
fit and into which I fitted the poly. I could see no way to allow for
drainage at the bottom of the sheets. Both ends of the sheets are
tightly sealed with caulk, and I  put more caulk at the bottom, to help
the sheets slide into the frame groove and to seal the juncture of
sheet and frame.

Now most channels of the poly look fine and clear, but a lot of them
stay cloudy from moisture (making for an unsightly appearance), and in
some channels several inches of water has collected at the bottom.

I don't understand why the channels are behaving differently. But more
importantly, am I stuck with this condensation/water problem forever,
because I sealed both ends of the channels with caulk? All I can see to
do to remove the water is drill a small hole at the bottom of the
affected channels and let the water drain out or perhaps pull it out
with a hypodermic syringe. Or perhaps the water will evaporate when hot
weather comes.

The weather in north FL where I am located has varied from the 30s to
about 70 since I installed the sheets. Will the problem get better or
worse when hot weather comes?

Thanks for help.

 The manufacturer, Poly-Tex, recommends *not* sealing the ends of the cut
sheets, for the very reason that you're describing.

Dave

 On Sun, 18 Jan 2004 10:11:59 -0500, Trent-Lion wrote:


Without knowing your setup, I am not so sure I would have been so eager to
seal the poly panels.  Moisture has gotten in several with nowhere to go.
If you can, remove the cloudy panels and let them dry complete.  Check
them for hairline cracks.  Once dried, you could reseal.  Since you are in
an area where temps aren't too extreme, I think you'd be safe not to seal.

You could also check the channels where they go and drill drain holes to
allow for drainage.  

Greenhouses aren't necessarily supposed to be airtight.  I'm not so sure
you really want to make the entire structure inflexible.

 It is raining and I can now see that the moisture in my twinwall
chambers is getting in *from the bottom*. Some of the chambers are less
well sealed with caulk than the others, water is gathering in/near the
groove in which the panels sit, and capillary action is taking over
from there, causing columns of water to form and mist to rise off the
columns and up into the chambers.

If I can ever get the moisture out, by drilling small holes and sucking
the water out with a hypodermic or however, I can perhaps seal it all
up so no more can get in.

Thanks for comments received.

 On Mon, 19 Jan 2004 11:11:05 -0500, Trent-Lion wrote:


Small vent holes near the top of each fogged channel would help.  I'd put
the holes on the inside surface, that which is away from the weather.  The
vents holes would allow trapped moisture a way to escape.  The holes would
not need to be any wider than 1/32 or 1/16", I would think.  It's worth
trying on one panel before committing to all of them.