Sounds like you don't need a BD screen in that room. May as well enjoy the purity of a matt white screen as you have the best environment to use it.
PS. Don't expect the Epson to get much dimmer after calibration, unless it is in a very odd mode at the moment. You may lose some brightness after calibration, but the Epson doesn't have a manual iris to control lumens and it's a fairly small screen size. Perhaps try an ND2 filter in front of it (but a decent glass one such as a Hoya HMC)?
"Don't believe everything you read on the internet". William Shakespeare 1615