Which venting option did they use? I have one, and don't notice it, but then again, I rarely open windows.
The thing burns extremely clean. Did they run the dual pipe setup where it is closed combustion? Did they put a trap on the exhaust for the condensate? Did they fill the condensate trap with water first? (although it would fill itself after running for awhile - internally, it does hold a fair amount of water to ensure that the trap actually doesn't get blown dry by the exhaust fan, until that happens, it would leak exhaust gasses).