I'm trying to make my porch into a seasonal "greenhouse".  I'm finishing up building my little house, and I'm in Texas so a big porch was obviously very important.  Now I'm working on gardening; I made a greywater bed (kind of like the earthship design) spanning the whole front length of my porch, facing SE.  Because its so hot here most of the time, and constantly getting water, I put a bunch of tropical food in there, and everything is growing beautifully.
Now, I know these plants can't handle a freeze.  It freezes here maybe a few nights (for only a few hours) in the winter, if that.  I guess I could just put a blanket on em and they'd be fine.  But, I'd be way happier if I could keep my porch/garden warmer than just "not freezing", not to mention the plants.
I'm looking into roll up vinyl curtains (too expensive, but I have sewing skills so maybe can make my own), or maybe can collect enough old windows to make removable "panels" and store em under the porch for the summer.  I know these options won't provide any insulation, so then I wonder about supplemental heat without racking up the utility bills?
I'm trying to balance ease of changing between seasons with durability and R-value.  It'd be a dream if I could keep it up to 40 or 50 in the porch garden on a cold night.  Any thoughts?
(Pardon the messy picture, its a work in progress)

Very cool!
I wrapped my chicken coop in clear vinyl shower curtains.
Cheap and sturdy for the price.
I have some vinyl flooring adhesive I think would work to merge the smaller curtains into a single larger peice.
Adding drums of water behind the bed as thermal mass is one way to "heat" that space.
A rocket mass heater is another.
I would plan on using an opaque insulative blanket pulled over your glazing from dusk till dawn,in order to conserver heat.

Darrell Frey wrote a great book about this in a colder clime in Bioshelter Market Garden.
John S
PDX OR

my question, looking at the pictures, is what would the frame of this seasonal greenhouse be? Are you just going to use PVC hoops? Are you planning on erecting a permanent wooden frame? My thinking would be a permanent wooden frame since your house looks so nice you want to keep it classy and then just buy a roll of greenhouse plastic. There is reinforced stuff that should last many years. As long as you aren't opening the 'greenhouse' often on the cold days it should stay nice and cozy.

Here are soureces for clear vinyl and FClean

https://www.bing.com/search?q=greenhouse+film+fclean&pc=MOZI&form=MOZSBR

FClean  has been in service over some greenhouses in Japan and other places, for more than 25 years without showing any signs f degradation.

it is also what is covering the biodomes at THe Eden Project in Wales.

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amleonard is a supplier who sells remnants for cheap. and you have a fairly small footprint to cover

http://www.amleo.com/poly-remnant-sale/a/35_11/

they update their remnants page often.

if you choose amleonard , i'd go with the Tufflite with condensation control, etc

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I have also over the years just used the vinyl by the yard at teh local fabric store, which can also be found online.

i'd go with something thicker . with vinyl, the gauge is : the larger the gauge the thicker the vinyl.

where as, with steel the gauging measurements are used differently.

overlapping it, starting at the bottom to protect from water coming in.

it does not have to be 'real thick' for this purpose. there is marine vinyl used for windows for boats and yurts that might be too thick.
In comparison, there is vinyl which is used for covering dining chair seats and more. anybody remember vinyl covered sofas and car upholstery
in the 60's?
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THis will also help to keep this side of your home much warmer too.

and wall  protected from weather! etc

GOod fortune on your adventures