Options for insulating small greenhouses

[Rivka]

So im putting in a 4x10 lean too greenhouse against two brick walls of my house, the long side has a sliding glass door on it, o the greenhouse will in a way be a extension of that room.
It is sitting on a painted wood deck, with pretty open slats ei very good drainage and probably upwards airflow.

The exposed sides point North and West the 10 foot side is North. So 2 story walls on the south and east sides. Not perfect, but its what I have.

The greenhouse is build with 4mm double wall Poly, and i am in a 7a area, the winters can get down to freezing for a while and snowstorms can happen, though last year for instance it only snowed one day. but also had 3 days of 15f.

I am probably planning to pulling my orchids back inside the house if it gets like that this year. But as long as i can keep things decent out there, i would like to keep most of them in place.

So what types of things work for extra insulation to make it easier to heat and a more stable temp?

A few things i have read about here and found online, would love folks opinions on their effectiveness

1. Insulation grade bubble wrap good because it still lets light in, does this stuff rally work, and i wonder how hard ti is to keep clean in-between it and the glass, were the bubble protein points, algae hell?? 2 rolls of this stuff would easily cover all poly surfaces. taping the seams of this might be a good thing to reduce air leaking out the top, but might make condensation bad.

2. Reflectix easy to get locally, might this be good for the back wall side? to maybe bounce light back into the greenhouse that hits the brick wall? or am i better to leave the brick exposed cause it could serve as a heat sink and stabilize things?


other ideas?


3. and for heaters, is there a functional difference between types of electric heaters? or is cost just a funtion of durability of they are all listed as "greenhouse" or "outdoor" heaters?
is something like this actually worth the extra money? is it cheeper to run, more safe or capable to run all night and day? than the standard $60 or $70 ones?


4. since we have at least one power outage each winter, fun fun, suggestions on a back up LP heater? I so wish i could run a gas line for this whole thing, but alas i am renting so that is out of the question.

5. general question about airflow, do you think that as long as i seal up the top of the greenhouse well, that i can control the air coming in from the bottom? i can seal that up, cause it is my drainage, and i thought about putting a matt down to slow the air down like astroturf, but I'm guessing that would cause damage to the wood by trapping moisture, so i think i have to let it be open and dry able.