In message , Franz Heymann
writes

"Robert E A Harvey" wrote in message
. com...

All very useful information to bear in mind.

I'm not sure about translucent frames being good enough for forcing
plants at the start of the year.

I may be wrong, but I am under the impression that the translucent
material does not necessarily absorb a significant fraction of the
incident light, but that it simply scatters it. If I am right, there
should be no problem about forcing plants early in the season.

If it is the same stuff as I am using (intended for conservatory roof
applications) it may transmit around 6% less light due to the internal
structure and being double skinned. But it more than makes up for that
by providing better insulation. I have known other cacti growers use
this stuff to great effect in their greenhouses (and intend to do the
same).

I'd be a bit less convinced by the 6mm grade. I reckon that may reflect
back as much as 10% of the incident light. But even then it may not be a
real issue since it is the warmth that encourages early germination.

Regards,
--
Martin Brown

"Janet Baraclough.." wrote in
message ...
The message
from Martin Brown contains these
words:


If it is the same stuff as I am using (intended for conservatory
roof
applications) it may transmit around 6% less light due to the
internal
structure and being double skinned. But it more than makes up for
that
by providing better insulation. I have known other cacti growers
use
this stuff to great effect in their greenhouses (and intend to do
the
same).

I'd be a bit less convinced by the 6mm grade. I reckon that may
reflect
back as much as 10% of the incident light. But even then it may
not be a
real issue since it is the warmth that encourages early
germination.

In Scotland, conservatory roofs use a triple walled polycarbonate
sheet for higher insulation still. You might find that even better
for
your GH.

I have a funny feeling that that is overkill, but I can't prove it..Do
you know of a source in which the heat transmission properties of twin
and triple walled polycarbonate are compared?

Franz