First off, I'm sorry if this has already been discussed. We are in the market for a new vent saw and believe we have it narrowed down to what we believe what will best suit our needs (rural department, therefore not much vertical ventilation and no industrial) We currently have a rotary saw with an aluminum oxide abrasive disc, and a standard chainsaw. As of now the general consensus has been to purchase the Univent vent saw to replace the rotary saw and keep the chainsaw with a carbide chain for wall breaching and such. I would like to know what the experience you guys have had with the Univent,or similar modles on metal roofing.