I'm looking for a good floor fan to take on job sites. I'm thinking about getting a 20" Airmaster from Grainger. It's a bit pricy, but anything of quality is. I like that it has ball bearing motor instead of sleeve and its rated at 3390 cfm. I know I want this style fan. Just don't know which one is best for our line of work. I want one light enough to pull up on a roof, but powerful enough to be worth using. I've used an old squirrel cage (out of old gas furnace) and a box fan for years. It's time to upgrade.