RFI shielding Basement

Clint, Since your basement is already below grade it is not likely you would have too much horizontally polarized RFI radiating from it. You might just consider putting in a decorative tin cieling like in old 1890's vintage saloons, The way the panels interlock might provide a good faraday shield for vertically polarized radiated rf from the basement. It could be electrically bonded and tied to waterpipes etc for a good ground. How about fine metal screen stapled to the botton of open rafter/floor joists. Perhaps you can find foil covered craft paper backed fiberglass insulation, staple it up then bond the seams with 3M foil tape? This would also dampen mechanical noise of a big iron system running. If not insulation, the heaviest wide roll of tin foil. Overlap the seams and staple up then cover with battens to accept acoustic tile cieling? Foil Backed foam panels etc. See what other truly conductive building materials you can find. They even make conductive paint these days. Your best value will be in conventional conductive building materials, not specialized RFI materials. Usually door panels on computer cabinetry are gasketed with spring finger stock to keep RFI leaks to a minimum, but usually there is close mesh and larger grates on the top of machines to allow cooling by convection. Sincerely Larry Truthan