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I bought an older house and it has a rectangle hole in the living room. It is covered with the register and it looks like an intake. I don't fully think it was used as an intake as the furnace is on the opposite side of the house. The house doesn't have the basement but only a concrete slab.

So there is wooden frame that holds the floor build on the concrete slab. This whole frame is in the shape of L and the missing part consists the furnace area. So the furnace area is not sitting on the wooden floor but directly on the concrete slab.

I'd like to know if there is a reason for that hole? There is a moldy smell coming out in my living room and I was wondering if I could just cover it. The hole look dry and I don't see any wetness in there...

Thanks.

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  • I'm sorry, I can't help you identify the hole (how big is it anyway?). However, if there is a moldy smell, I would be concerned about it! You might want to determine just what is causing that - moisture of some sort, but of what cause? Leaky pipes? Water infiltration from the exterior? – aaron Aug 12 '14 at 15:21
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    A picture would be beneficial to this discussion if you can provide one. – James Aug 12 '14 at 15:35
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    @iStimple, I already found all the treasures. It's all over the house. It's called dust and cobwebs. lol – Grasper Aug 12 '14 at 16:14
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    Can you detect airflow through the register when the furnace is running? You might want to see if it will hold a piece of paper down. – Comintern Aug 12 '14 at 17:26
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    The floor is raised off of the slab, or "furred up" as I call it, for a reason. I am thinking this hole was installed to allow air movement between the subfloor and slab due to historical moisture (wet slab) issues. – Jimmy Fix-it Aug 13 '14 at 5:15
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It certainly looks like a setup to move air across under the flooring back to the furnace - either a cold air return or a heating vent, depending which way air moves when the furnace is running. If no air moves when the furnace fan is running, its purpose is harder to infer. I'd guess cold air return. In either case plugging it it probably will hurt your HVAC performance and not help to mitigate any mold issue you have.

The moldy smell might or might not be directly related - old carpet itself can be a direct source of moldy smell in my experience - moreso if it's concealing some source of moisture. But I admit to not being a fan of carpet in general. Might try a serious "steam-clean" on the carpet (no actual steam may be involved, depending on system used.)

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