Permanent opening from crawlspace

Hello. I was curious to see what concerns (if any) there might be with this. A permanent opening by way of an air duct grille is installed below and water heater and adjacent to a furnace and behind an unsealed bi-fold door. I can see directly into the crawlspace which has bare earth and is not sealed off by any means. In a previous post, a duck gained entry through an unscreened vent in masonry block. Anway, if a duck can get in then a snake can get it or a mouse, spider or a big roach. You get my drift. There is one opening in the top of the ceiling from the attic space. It is my understanding tht the opening in the attic should not be screened, but how about the one from the crawlspace?

Sopha Inspection 012.jpg

I would have put a screen over it. My gues is that it was there for combustion air for the water heater.

Thanks James. No doubt it is for combustible air. I was asking if that grille can be screened in order to ward off unwanted guests? The attic vent through ceiling cannot. Since the crawlspace is unsealed, cool damp air can enter, but that’s the way it was designed.

Hi Hank,

I agree, not only does the duck show that the crawl needs sealing, and the grill could use some proctection. But also the stains on the subfloor suggest that a moisture barrier should be in the crawl as well.



Yep this is for combustion air…But here are my concerns…

Radon and or moisture issues too. …

You pointed out this has a dirt / soil floor in the crawl space.

In this case you can do two ducts coming from the attic. One high and one low ( coming close to the floor) to supply combustion air . It was easier to do it this way but if you have a Radon issue this is not a good approach. :neutral: