The siding is probably polycarbonate sheets. YouÂre in BC? How cold do you expect the nights to get on the average? I suspect all the gallon jugs would eventually drop to freezing way before the night is over. I think putting a small electric space heater (or other heater) will be needed to keep it above freezing. ThatÂs what I use. I also have a remote min/max thermometer so that I can check my night temperatures in the greenhouse daily.

That is what my dad is trying to aviod. The electric bill is killing him already. It only goes a couple degrees below freezing this time of year and is getting slowly warmer. He does not intend to use it as a year round greenhouse but as a place to extend his season.