So long as its for stopping heat loss NOT protecting against frost, then polyethylene insulation is fine. Any more than 25mm wall and the increased cost isn't, generally, rewarded by savings. In terms of fixing, if you zip tie and squash it you lose its efficiency at that point. Actually best to use electrical tape (about three wraps) and do it just so the gap closes.
Physically, this type of insulation begins to shrink at 4 degrees centigrade (+4) so gaps open up and you lose heat. Nitrile based product (armaflex etc) does too, but that can be fitted so you can compress the lengths by 10% to compensate for this shrinkage. The grey stuff cant be compressed enough to compensate.
PLEASE. Only ever fit a nitrile product when trying to protect against frost. NOT ONE manufacturer says their grey (polyethylene) product protects against frost...