I thought I would share with you all, this is the third time I have seen this there are no vents in the crawl space just the vacuum under the house on the far East side next to the furnace, its termination point is next to the A/C unit (which is fine). However on the far East side there is some mold noted below 9 sqf. So does anyone out there no the benefits of this unit?
Does it cost lest to put this in versus pouring for the vents?
Feed back would be great.
Is that being used for Radon mitigation?
No just to keep the air in the crawl (good) Radon is very low here my tests have shown less than 1.0 pcl
Let me just say if it is they dont know it.
So it’s in exhaust mode and not supply?? May be trying to imitate a system invented by a guy I knew in my old haunt of New Brunswick- The Humidex. Will “work” in certain weather and cause problems in other!!!
http://www.humidexatlantic.com/content/humidex-solution/humidex-vs-dehumidifier.cfm
More later…got to go!
Troy, I have also seen this type of unit used for clothes dryer venting on long runs.
I’ve only seen pix but I think you’re on to something here…metal pipe???
I could see no other purpose.
Did the pipe originate under a barrier or slab and exit the exterior or through the roof?
Reminds me of a consulting job I did for Sears Indoor Air Quality division 5-6 years ago.
They were called to fix the problems with the long (40-50’ or so) dryer duct runs in a newer condo, charged the condo over $4,000 but their fix didn’t work. I ended up recommending units like that (Fantech) controlled by pressure switches.
The metal duct that moves the air is only about 2 feet long it comes up under garage floor area and terminates to the vacuum. The airflow terminated through the garage wall to the exterior near the a/c (its got good air you could probably blow dry your hair not mine)
I quit blow drying after this incident
isn’t it funny the things we do to pass the time.
we are so easily amused
The end under the garage floor area is open to the ambient air and does not go under a concrete slab?
How is the system controlled? Is there a dehumidistat as a main control or is it simply a switch? Or a 24 hour timer?
Yes, It comes up through the crawl next to the furnace which is the firewall area (but up through the ground) No switches were noted in the area of the vacuum, no thermostat was noted (outside temp was 26 degrees and snow)
Continual sucking was noted 
sorry for ripping off your question, bad-bad badair 
No worries
Was there a ground cover of plastic to act as a moisture barrier for evaporation from the soil?
If not, this may be there to suck moist air out of the crawl space. Not a very good approach to controlling /dealing with ground moisture evaporation. Along the lines of the Humidex idea for summer humidity in full and partial depth foundations.
Another pic to add to the whole thing.
This just dawned on me, this pic is a return in the west hallway on the wall close to the floor. See how it terminates in the crawl (I’m assuming what would you guys think?)
Vapor barrier is good throughout.
Just a note: Temp in the crawl was a nice 64 degrees with a RH of 36%
So they are drawing conditioned air from inside the house and venting it outside through the inline fan motor?
Now I am confused.
Me to, I have put a call into the builder but have heard nothing yet