WAS CURIOUS TO ANY OPINION ON INSTALLING A HUMIDIFIER ON DUCTBOARD. NEVER HAVE BEEN A FAN OF IT, DUCTBOARD EITHER. HAVE BEEN TO JOBS WITH UNSERVICED HUMIDIFIERS AND SEE GROWTH EVERYWHERE. AS A TIN KNOCKER,LOVE MY METAL BUT ON EXISITNG JOBS IS THERE A POINT TO CHANGING THE SA PLENUM TO METAL? ADDS COST TO THE JOB. THANKS FOR READING.