"mmccaws" wrote in message roups.com...
So I'd like to hear what folks do to better insulate
those glazed surfaces.

Bubble wrap works wonders.

I built my greenhouse with 8 mm twinwall on a wooden frame. After the
first winter, I did the following:

1. Covered the north wall with "Reflectix" insulation stapled to the
inside of the frame. Reflectix is the brand name of a product that
consists of bubble wrap sandwiched between two layers of foil. By
using it on the north wall, I get light reflected back into the
greenhouse and a layer of dead air between the insulation and the
polycarbonate of the north wall.

2. Covered the east, west, and south walls with clear bubblewrap
pushed against the polycarbonate and stapled to the frame. The only
surface that is exposed polycarbonate is the south facing slope of the
roof. The bubblewrap stays up until about the middle of April, and
then I store it in the shed, because I want the greenhouse to loose
heat more rapidly in the summer.

If you don't have electrical conduit and hanging pots in the way, you
could staple a single sheet of polyethylene across the inside of the
frame instead of using strips of bubblewrap.

3. Added a flap of polyethylene inside the door to make a simple
"airlock."

4. Sealed the exhaust fan and intake shutters with styrofoam and
polyethylene from early December to early February. Once temperatures
in the greenhouse start reaching the low 90s during the day, I remove
the insulation and allow the greenhouse to vent. But I still replace
the styrofoam at night when temperatures are below 40 F.

Next time I build a greenhouse, I'll use triple wall, make a solid,
insulated north wall, and have a long south facing shed roof instead
of a symmetrical roof with gable ends. I will probably be more
careful where I put the electrical conduits, so I can more easily
staple a layer of clear polyethylene inside the frame.