The pvc stuff will, at best, keep chickens in. It won't keep predators out. Windowscreen either, of course, and I wouldn't even count on windowscreen keeping all chickens in.
If you are going to try to keep rats out, you NEED 1/4" hardware cloth, and preferably a good cement slab as well. You may or may not succeed, though, b/c rats are very squish-down-able and very persistant and only need to find or make *one* little gap and they're in.
If rats are not an issue but budget is, and if your chickens will be locked up every day from dusk to dawn without fail, then a reasonable compromise is either a) use heavy gauge 1x1 wire mesh, or b) use heavy gauge 2x4 mesh or chainlink and run some smaller mesh, ideally hardwarecloth but could substitute 1/2" chickenwire if you can find it, or even 1/2" plastic netting if you feel brave, inside the bottom 2-3' of the run walls to prevent reach-through.
Using something not very predator-resistant is IMHO false economy, because not only will you have to replace it once predators do eventually eat your chickens (which is not guaranteed but pretty likely at least in the long run, and in fact happens to all too many people in the *short* run), and replace the chickens too, but you will also have a much TOUGHER task thereafter, because there will be predators around who KNOW it's worth extra effort to try to get into the coop/run because there's some tasty snacks in there.
Good luck, have fun, go browse the Predators and Pests section of BYC, I am not kidding,
Pat