Originally Posted by Bob3

Yes & yes.
Built from scrap materials, the plastic cover is the only thing that cost any $$, it takes about $12 worth of plastic sheeting & duct tape every year.
It's a "lean-to greenhouse" in the winter & during summer the plastic comes off & a strip of shade cloth runs along the top 4'.
(It's on a south facing wall.)
Here's the winter configuration:


A box fan on thermostat draws warmer air from under the house when temps get below 40°.
A backup water mist is set to come on at 34°, which hasn't happened in the 4-5 years we've had it set up this way.