Regency E21-LP1 - Manual (Page 7)

7 Regency E21 Gas Fireplace Insert
CLEARANCES TO
COMBUSTIBLES
INSTALLATION
The minimum clearance from the side of the appliance to a combustible
side wall is 9 inches (229mm). The minimum clearance from the top of
the louver to a combustible mantel is 14 inches (356mm) 14 inches (356mm). The minimum
height from the top of the louver to the ceiling is 36 inches (914mm) 36 inches (914mm).
See diagram.
Note: A non-combustible mantel may be installed at a lower height
if the framing is made of metal studs covered with a non-
combustible board.