I do quite a few 11 Month Warranty Inspections in the Phoenix Metropolitan Area and most houses will have a AprilAire Fresh Air re circulation fan in the attic to draw fresh air into the HVAC system from the exterior. They will either respond or they don’t, the biggest issue is the home builders will not install a manual override switch which is a requirement according to the installation manual. Today I ran into a house that had the Manual Override switch installed and labeled “Fresh Air Re Circualation Fan”, however, when I got up into the attic, they had an exhaust fan (Broan AE50110DC-A bathroom fan) exhausting to the exterior. Fan to the exterior and that was it. I ran into this a couple weeks ago and wrote it up to verify with the builder it wasn’t suppose to be a recirculation fan. After today’s inspection (different neighborhood), I now wondering if this is something new I’m going to start to run across and whether I need to write up anything or not. I did write it up again today. Anyone have any thoughts on this or has anyone seen this. By the way, both instances have also been sprayed Polyurethane foam for the insulation.
We don’t have many conditioned attic spaces in my area, but I’d rather see the stale air exhausted to the outside than not exhausted at all.
When asked, I say that I prefer a supply and return vent be installed to serve the conditioned attic (if a forced air system is present), but a bath fan to the exterior is better than nothing. In my opinion, it would be best to have it on a humidistat or some other automatic control because I don’t see the homeowner remembering to periodically vent the attic space.
A few weeks ago I was asked by the homeowner and their remodeling contractor to help diagnose where the icicles were coming from on the pic below. Turns out they had foamed in the attic (moving the thermal envelope to the roof deck) and blocked off the original attic ventilation. They turned the space into “conditioned” space that had no ventilation, thus the moisture build-up.
From what I gather from your post, you are talking about two different ventilation systems (or maybe not).
- Fresh air piped from the exterior to the HVAC system generally does not have a separate fan, other than the unit indoor fan and a balancing damper. There is no reason for it.
2nd option which I think your describing is a heat recovery system (Heat also meaning Moisture).
The Aprilaire 8145 Fresh Air Ventilator is designed to bring in precisely the right amount of outdoor air into today’s efficient homes. Integrated controls allow the ventilator to be hardwired. Powered damper is removable. Washable MERV 6 filter included.
The 3rd:
This fan is to vent attic air from the attic to control heat in the space.
They all have a specific purpose.
Recommendation; I suggest that you follow the HI SOP and not try to analyze how things are put together. None of the three above are “wrong”, or as the SOP states, “Significantly deficient”. How things are built is the job of the local building code (which is not your responsibility either). It’s not good for your reputation to be calling out things that are not the same thing you’re talking about.
It’s great that you learn this stuff so you can understand when something is significantly deficient. The fact that a switch is not there, but in a parts manual, is up to the design engineer / architect. Parts are used different ways on site, sometimes for a specific reason.
As for the Broan AE50110DC-A bathroom fan, we could discuss if this is the correct fan for your area and application. But as facts are limited, we have nothing to discuss in this matter. Those shaded pole motors in high heat, high static pressures from a foamed attic, likely do not meet the service factor. I don’t know… 
Versus;
I concur. AprilAire Fresh Air Ventilation HRV’s tied into forced air ductwork.
If not, there has to be separate supply and/or return ductwork when ductless mini split heat-pumps combined with electric or hydronic baseboards or convection wall heaters are used for heating/cooling.