Several weeks after having the blown in insulation installed, I noticed what appeared to be quite a bit of dust behind the heating return grate in the living room (we have a forced air heating system). Then it hit me like a ton of bricks, the return, like many older homes, actually uses a section of the wall cavity as a heating duct. After removing the grate, my fears were confirmed. The entire return and the main return duct in the basement, were packed with insulation!!
I immediately rushed into action, removing as much of the material as I could from inside the grate itself. Then I went into the basement and cut a hole into the main duct to remove the rest of the insulation that had found its way into the system - what a mess!!
But a couple of hours later and I had most of the insulation out, although I will have to vacuum out the filter in the furnace several times in the coming weeks to remove any remaining material that finds its way down. Many of you with bungalow style homes who decide to go with blown in insulation may end up with a similar situation if you have forced air heat. Hopefully for your sake its not a problem for you, but it's worth checking out just in case.