I will start here in the general section in the hopes it will catch someome's attention. I have a 2 cylinder 1800 rpm Lister15 HP belt-driving a 5 KW Kato alternator. It is located in a bunker between two buildings and partially below ground. The top 2/3 of the structure and the door are all conventional frame. I would like to reduce the mechanical noise from the Lister without making the enclosure 6'x4' by 7'high too hot. At present, a long run will raise inside temp to about 120 F. I am thinking a double wall and ceiling with vents in the roof and at floor level. Anybody else been there? (The exhaust noise is acceptable as I presently have it with 2 mufflers in line and the outlet pointing up.) dp