After a morning trip to the Botanical Garden, we spent a good chunk of Sunday afternoon winterizing our sun porch.
When we found this apartment, we were really excited about the south-facing sun porch, since it would get lots of sun (and solar heat) in the winter, meaning we could leave a lot of our potted plants out there instead of crowding them inside with us. And while the porch did get fairly cozy last winter (except on the cloudy days), the heat dissipated all too quickly once the sun went down, leaving our plants vulnerable to freezing temperatures.
Our first step was to buy a small space heater. It’s a milk house heater, and it has a setting where it will only kick on when the temperature dips below 32°F (this feature is not perfectly reliable, but it worked alright last year).
We realized that even on the lowest, “prevent freeze” setting, this thing was going to be running all. the. time. on our drafty, uninsulated porch. So at some point in the middle of last winter, we bought one of those window plastic kits in an effort to seal things.
It really made a difference in how much heat the porch retained, especially on windy days. When spring arrived, we peeled off the plastic and realized it was in good enough shape that we could probably fold it up and reuse it.
The double-sided tape, however, definitely needed to be replaced. The big box home improvement store we visited only sold the entire kit (which meant new plastic that we didn’t need), but we found a small hardware store that sold just the double-sided tape. Of course buying the tape alone cost more than buying the kit — argh!
In the end, we had enough tape leftover from the two kits last year, and our reused plastic sheets worked quite well. We rearranged the tables and shelves to maximize sun exposure and cleaned up a bit, while we were at it.
You can’t really see the plastic in the photograph, but it’s there. This arrangement leaves enough space at the table for me, so I can spend some time out there on the warmer days. We got this up just in time for the cold weather tomorrow.
On the one hand, it seems a little crazy putting the various resources (our time, electricity, plastic and other materials) into keeping some potted plants alive, but the fact that a number of them are edible (herbs, lemon and key lime trees) justifies our efforts a bit, and it really is a lovely space now. With the exception of very cold, cloudy days, the heater will only run at night, and perhaps not every night, depending on the severity of our winter.
Her Green Life 
I used to have plastic on my windows and it made a HUGE difference. But that was before the adorable, yet challenging, Smoky Bear Kitty came into my life, and decided that the plastic must be there for the sole purpose of giving him something to shred. Of course, he also decided that all house plants must be there for him to eat and/or destroy, so they had to go too. Sigh.
Anyhow, I’m hoping that I’m misinterpreting that photo, because it looks like the storm windows are open, which would sorta seem like it wouldn’t help much in terms of keeping the place warm!
Have you thought of adding some sort of a thermal mass to absorb heat from the sunlight and radiate it back at night? It wouldn’t have to be anything fancy… a big barrel of water would probably do the trick. It would probably cut down on the amount of electricity that you had to use to keep it from freezing at night.
My parents have a similar room and the other thing they have done is to install insulated shades. They have fancy schmancy ones that run in these little tracks and form a nice seal like these: http://www.innovativeopenings.com/wp-content/uploads/2010/08/Livingroom-Open-Good-Valanc-306×400.jpg. I made something similar for a few of the windows in my house only they’re just attached around the edges with velcro. The only problem is that you have to shut them every night and open them each morning which is, ahem, more work than I’m generally up for!
The porch windows are shut. They’re basically the old triple track storm windows, so what you see that looks half open are the metal frames of the window screens, which we left in random positions. We have a couple of 5-gallon buckets back there that usually have some water dechlorinating for the plants, so I guess those can serve double duty as thermal mass!
Remembering to shut those shades every night and open them every morning would be a downside!