Of course, I have to try this. Years past I would just put a pail out over the iris or a plastic "tent". I never thought of "clothing" nor a heat source. Here are some pictures of this years effort.
The first "cage" is bigger than what Griff was talking about as he was covering on rhizome at a time. The first cage is covering three rhizomes. One "Autumn Circus" and two "Haunting". I did the Autumn Circus because it was right next to the Haunting pair, otherwise I would have left it out in the cold. The second picture has my "Again & Again" "clump that still has three stalks yet to bloom.
The second cage is on just one rhizome and it is an unknown (so that is why it got caged).
I have used the light-bulb idea under a plastic sheet covering a small lilac bush in bud during a Spring freeze. It works very well. Yours is much more fancy with a string of Christmas lights!!
Thoughts become things -- choose the good ones. (www.tut.com)
I did stop the single iris enclosure. I cut the stalk and brought it indoors. It was not well and did not bloom. However, I was able to take the bud apart and I am 95% sure that the rhizome is "911 Remembered"!