Greenhouse Temperature on a Below Freezing day

It’s hard to believe it gets over 100 degrees Fahrenheit on a sunny day, but it does. I built this greenhouse for performance and appearance. I was trying to make double poly film look as good as it performs. This is a fully insulated greenhouse on the back of my garage. If I wanted to deep winter grow I would add black water barrels and a roll down insulated blanket. If I had a lower budget I could do a single layer with zipper doors or a roll up front curtain. I get between 60 - 80 days extra growing per season for my super hot peppers.