Installed an 18-TR late last winter for shoulder season burns . The furnace is just too much in 30 degree weather. Fired it up tonight for the first time with a quarter load of 3-4 year old beech and HOLY SCHNIKEYS is it hot in here (30 outside)!! Flue damper shut all the way and shes screamin'. Could I possibly partly close off the air wash holes with fiberglass to slow this thing down?