I'm chiming in with a quick update:
about 5.5 years ago I build a very robust coop. I decided to frame it and evnvelope the frame in hardware cloth before adding siding and roofing so that it was essentially seamless... I grew up on a farm, I know what rats and predators can do and was determined to pay it forward with the hard work up front so I didn't have to hassle later. for the bottom, I ran the hardware cloth 2' down at a 45 degree angle, as recommended by some, with the idea that the vermin would get discouraged as they dug down and give up. fast forward to about a year ago when I noticed that the hardware cloth was rusting heavily below the ground level. I did not leave much of an eve and apparently the nutrient rich soil inside the coup, combined with rain water dripping off the roof and directly on the fence were it entered the ground, significantly sped up the oxidation process, as hardware cloth should be good for somewhere between 10-20 years below ground if kept relatively dry. life got busy and I did not do the prudent thing, which would have been to reinforce it before something dug down and found a way in. about 5 months ago, a rat made it through, and that was the beginning of the problems. once I noticed the breach, I dug up the perimeter and added new hardware cloth and took plastic liner and covered it to protect the hardware cloth from rain. apparently i trapped a rat inside and that little bugger dug it's way out and apparently introduced all it's friends to it's new found mother load of chicken feed. I've been battling these rats ever since. I've killed many, but a few have survived and grown ever smarter at ways around my new tricks. i've used just about every type of trap you can imagine and I keep thinking I've gotten them all only to find there is at least one more. they have dug holes undermining major supports and generally run amuck of the place. it's been a very humbling experience for me. I'm about ready to dig out the entire underside of the coop and add a hardware cloth layer across the whole bottom, making it absolutely seamless, wall to wall, ceiling and now floor.
The two things I want to pass on to folks who are considering using hardware cloth throughout the main coop, is that it is not enough to go two feet down, that it's necessary to go underneath the entire coop as well, assuring no more than a half inch gap anywhere. the second thing I'd like to pass on, is the need for adding adequate eaves to keep the water away from the hardware cloth as it goes into the ground.
For the most part, I am very happy with the coop I built, I have not lost a single bird to predators, and up till recently, have not had to battle rats... but do wish I had spent the extra money up front to go underneath the coop with hardware cloth and added extra eaves. digging out the coop and adding hardware cloth now is going to be a lot more difficult that it would have been during the original construction phase.
oam
.... thought it might be the heat exchange 
