I have a crawl space below one room ...sitting on exposed dirt. It has a return plenum running through it that I would like to remove. The plenum does not lead to anything or any room that takes return air to the furnace--it goes nowhere. (Seems it was part of an old addition that was abandoned perhaps.) I would like to remove this plenum because I believe it just sucks musty air through its gaps out of the crawl space into the furnace and spreads it through the house. Are there any question marks or concerns about doing this removal? Thanks in advance.

I need to know if I'm thinking this through correctly....I have a large space: kitchen, eating area and small family room on the afternoon sun side of a ranch home. There are 5 supplies for the cold air and one return that is tucked underneath a desk area. (which I use and currently has a CPU/Computer tower tucked inside it as well) This cold air return has (2) 8-inch ducts pulling air as best it can from the area. [ATTACH]53527[/ATTACH][ATTACH]53528[/ATTACH] My concern is that because of its location (the desk obviously was an afterthought post design!) it's not pulling as much air as it can - hence the struggling temps in this room... [ATTACH]53529[/ATTACH] Because the desk has a cabinet over the top of it, I'm thinking of maybe somehow opening up the channel in the wall between the studs and breaking out another grill above the cabinet to increase air flow - plus it would also pull the HOT summer air and I could damper it (closed) for winter use when air flow isn't such an issue as there is a fireplace in the small family room. The thermostat for this floor of the house registers 4-6 degrees lower than in this room in summer and sometimes higher in the winter (but I run the fireplace too so it's hard to tell). Currently there's a 2x4 on the upper side of the existing return....it appears that it's more than 1 16" stud span, but not quite 2 full spans of the studs - there's a strange "floor" constructed under the floor joists to enclose it.... [ATTACH]53525[/ATTACH][ATTACH]53530[/ATTACH] Any thoughts would be welcome! There's a gale force suction happening under this desk but I think it's insufficient due to its location not being on an "open" wall..... Pam