I don't have to insulate my greenhouse where I live other than taping up some plastic over a few leaky areas in winter to keep out draughts, but I have heard people say that BUBBLE WRAP works very well on smaller size greenhouses. You just but it in rolls and tape it to the inside walls. Its clear and allows light through while conserving heat

Chris,

You might want to try the bubble wrap - it is very light in weight and inexpensive. I've only seen photos of your type of greenhouse, but don't think the solar pool cover would be a good idea. First, it's going to cost you about least half as much as your portable g'house; the lowest cost one I saw was, I think, around $80. Also, they are quite heavy and I don't know if your frame is built to carry that kind of load, especially if you get a late snow. So far as I know, everyone uses the "clear" type of solar pool cover (it's actually kind of cloudy-clear), so lets a good amount of light through.

I don't know how cost-effective it might be in that type of structure, but if you get strong, cold winds predominantly from one direction, you could probably stand a sheet of rigid foam insulation inside that wall ... just don't block the sun from coming in your south-facing wall, and try to allow in what morning and afternoon sun you can.

Hope this helps, and good luck with your peppers. Are you starting anything else?

Diane