Soffit Vent Exhaust Cap

[TJanak]

My HVAC guy installed these soffit vents for the bathroom exhaust fans in our new construction. https://www.homedepot.com/p/Everbilt-4-in-Spring-Loaded-Exhaust-Hood-in-White-BPSH4WHD/203626494 We have wrap around porches so they are actually installed in the porch ceiling near the outside edge. They look nice and are spring loaded so I appreciated what I thought they would do.

I also purchased some nice Panasonic exhaust fans https://www.build.com/panasonic-fv-0511vq1/s1400393?uid=3309191 that has an ECM controlled motor that supposedly can maintain ideal CFM's with regard to variable back pressure. 110 CFM.

My issue is that these exhaust caps only open 3/16" or so when the fan is running. I can't imagine that is enough space for a significant amount of airflow to exhaust from the bathroom. I'm not sure if the issue is spring pressure on the damper/lid, or negative pressure in the house. Entire house is spray foamed but we have make up air that is tied into each dehumidifier which is tied into each air handler on each floor.

Thoughts?

 

[Fitter30]

Fan on high speed?

 

[Sponsor]

 

[TJanak]

Fan on high speed?

Yes, made sure of that.

I'm really questioning the negative pressure part of this. For fresh air intake we've got a 4" wall cap and 12 feet of 4" duct running to the dehumidifier. Then has to pull through the dehumidifier filter, then through HVAC ductwork into the house.

We should be in the house in a week, guess I'll take a shower then and see how they work.

 

[Fitter30]

With everything running,, house closed up crack a window with a match or piece of toilet paper see what way the air flowing.

 

[john murdock]

My HVAC guy installed these soffit vents for the bathroom exhaust fans in our new construction. https://www.homedepot.com/p/Everbilt-4-in-Spring-Loaded-Exhaust-Hood-in-White-BPSH4WHD/203626494 We have wrap around porches so they are actually installed in the porch ceiling near the outside edge. They look nice and are spring loaded so I appreciated what I thought they would do.

View attachment 68941

I also purchased some nice Panasonic exhaust fans https://www.build.com/panasonic-fv-0511vq1/s1400393?uid=3309191 that has an ECM controlled motor that supposedly can maintain ideal CFM's with regard to variable back pressure. 110 CFM.

My issue is that these exhaust caps only open 3/16" or so when the fan is running. I can't imagine that is enough space for a significant amount of airflow to exhaust from the bathroom. I'm not sure if the issue is spring pressure on the damper/lid, or negative pressure in the house. Entire house is spray foamed but we have make up air that is tied into each dehumidifier which is tied into each air handler on each floor.

Thoughts?

I had these vents in my soffit and ended up with moisture collecting under the soffit. Wish I hadn't done it.

 

[TJanak]

I haven't noticed moisture collecting under the soffit, but guess I really haven't looked after a shower (it's dark). Usually have some kind of breeze here though. Thanks John.

We've been in the house a month and our bathroom mirrors or window doesn't fog up so I guess it's moving enough air. Though one night I forgot to turn on the fan before a shower and the mirrors still didn't fog up. But the bathroom is big and we have a whole house dehumidifier so who knows...
Kids have been using the other bathrooms but I haven't tried them yet.