Crawl space fan is causing smell coming from attic?




You really seem to have the answer for everyone’s problem, Mr. Bibler. How long have you been a full time home inspector?

James you never gave a reply to our questions

Please state your where you stand.



We don’t bring the toys we play with in the cesspool to the open board, Mr. Bibler.

Are you embarassed to tell us how long you have been a full time inspector? Are you a full time inspector…or is home inspections just an offshoot from your pesticide treatment business?

Tell us…do you suggest to your customer who has a house infested with termites to “leave a window open” so the termites can leave?

I don’t think you have ever been a full time home inspector, Mr. Bibler. I think you are a full time termite inspector who uses home inspections and IR to get exterminating jobs. Am I wrong?

Just curious.


Let just say Ive been around long enough… There are 4 Building inspection companies in my family dating back to 1947 from L.A. to San Francisco. Ive been doing inspection for a long time… But thats not the point in fact I don’t see a point in why you would even ask a question like this…

And yes more people do need to open more windows and let some fresh air in… You should try it sometime James you just may come away with another perspective on life… Look for the good in People James… You will find it…

I’m a nice guy.:mrgreen:. And I bet your a nice guy too… May even want to have a beer with you some time…



The sad part is that I heard MU’s mold expert is a Certified Industrial Hygienist (Not a full Industrial Hygienist) and he is not certified in mold. I have heard out his mold assessments.](*,)

Ron, broad sweeping statements like this one are not healthy. Here in southeastern VA, and most of the entire southeast of the US, a vented crawlspace is a bad idea. Those fans would simply suck 90% humid air into the crawlspace. The better fix is to eliminate that outside air from entering the space all together, at least in this area.

Correct me if there is a flaw in my logic…

A) Crawlspace requires power ventilation because of moisture/mold.
B) Ventilation system successfully draws moisture and mold out of crawlspace, but also draws “smells” from attic.
C) Attic has moisture problem, that is being (at least partially) ventilated through the crawlspace.

If this were all true, and the crawlspace vent was drawing from the attic, wouldn’t the logical conclusion be that the crawlspace ventilator, actually be helpful with the attic moisture problem in this instance?

Don’t get stuck on ventilation as the only and complete solution for a crawlspace and/or attic moisture problem.

If the depressurization being talked about here is strong enough to suck air from an attic down into the crawlspace, it also might backdraft naturally vented gas appliances at the draft hood…not a great situation.

Unvented CS I feel is defiantly the best .
Seal every thing correctly and if needed add a dehumidifier set at 50% and leave it on with proper constant method of removing the water from the dehumidifier .
This method has always worked that I have seen when properly done .

You would think.

Sorry but Ron has a good point here.Cooke to has good answer but I am getting confused to get my head around the question in full .To many answers, to many building possibilities.

Sounds like many on this thread are confused.

The crawlspace ventilators mentioned are low flow and low pressure. I think we are looking at about 5 Pa.

The ventilated crawlspace needs to sealed with respect to the outside. That may sound contradictory, but you can’t draw hot, humid air from the outside and cool it in a crawlspace and expect it to dry. The exact opposite of drying will happen if the crawlspace isn’t ventilated. The existing crawlspace vents must be sealed.

Yes this will draw conditioned air from the building into the crawlspace. It’s not as much of an energy waste as you might think. Many homes have uninsulated basements that run dehumidifiers all the time. Some basements are at least partially conditioned and aren’t occupied. In fact, this type fan could actually retard some of the stack effect losses which are greatest at the attic interface.

These fans could not pull smells from the attic. They just can’t generate enough static pressure. That logic just doesn’t hold.

  1. A damp and moldy crawlspace stinks.
  2. The stack effect will draw crawlspace air into a home
  3. The house now stinks like mold.

A crawlspace ventilator can reverse this. It sounds like the “attic smells” excuse is just an invalid conclusion thrown out so that they don’t have to stress their minds with different information.

The problem with your ventilated crawlspace “theory” is with your logic.
The problem with your logic is this: when it works then they can’t sell waterproofing services!! So obviously your idea is flawed since it doesn’t fit their business model of selling expensive services.

And I just don’t see many attics that smell worse than the crawlspace.


Could you not use a smoke pencil to find where the back drafting is coming from.The home will be uninhabitable if this persists or might already be.
I installed turbine vents for this very purpose and reason being that the home was not venting properly.IE: same story but non sealed building.
The turbine would have a pot installed directly underneath it and would be equipped with up to 4 mounts to attach a 1 to 4 inch hose (styled like a dryer hoes only more rigid but allowing them to be able to be fished through wall or bulkheaded and installed where they where needed.The vent would be able to be opened and closed and adjusted for whatever desired drafting and air flow was required.
Sounds like this building should have adjustments to its venting problem for it already sounds unhealthy to live there.
When was the residential building constructed.Might have been the infancy of that type of building practice and errors were made by contractor.