The plenum for the furance/a.c. is located in a vented
crawl space of my home. It is supported by the floor joists. I was able to insulate under the bottome and most of the sides and ends with Reflectix insulation. However due to condensation drain pipe and other running pipes, I cannot get the Reflectix on the top. My question is: Can I run R-19 insulation into the joists cavitiy (which I ...