Ventilation issues / high humidity in new bathroom - Panasonic FV-08VQC5


  #1  
Old 03-01-17, 04:39 PM
S
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Received 0 Votes on 0 Posts
Ventilation issues / high humidity in new bathroom - Panasonic FV-08VQC5

Greetings,

New bathroom (old house, moved walls, re-arranged kitchen and adjacent bathroom).
Bathroom size is a little over 40 Sq. ft. in first floor. Bedroom above it.
Everything is new. Fully insulated outside walls. The entry is from the mudroom and the other long wall separates from the kitchen.
It has a roughly 42X34 shower with sliding glass doors.
Has a toilet with in-wall carrier and a sink next to it.
(You probably say "who cares about the details"; thought I'll provide all the details to avoid questions )

I wanted a quiet and "sophisticated" fan in this bathroom so I installed the above mentioned Panasonic FV-08VQC5 with both motion and humidity sensors.
Fan comes from factory with settings at 50% humidity and 10 minutes (motion) as default.
When we first powered the fan I noticed that it was working non-stop. I figured that it "sensed" high humidity so I changed it to max so that only the motion sensor will work and changed the timer to 5 minutes (continues working for 5 minutes after person leaves bathroom), I thought it would be fine.

We just took the first shower a few days ago and the next day my wife reports that water is dripping from the fan. Not even during a shower; the last shower was the night before.
I took the grill off and saw a hole (see pic) with drops of water sipping out. My thought was that the fan did not work long enough after the previous shower and water condensed in the channel above it and simply drained through this hole, which I assume is by design (I certainly did not drill this and the fan is brand new ).
I also changed the settings again - humidity back to 50 and timer to 10 minutes to allow it plenty of time to clear the air after a shower.

Earlier today my wife calls me again - she was taking a shower, water dripping from the fan and the entire bathroom walls...all of them, soaked with water (humidity) as in - the fan didn't exhaust anything out.

I checked the vent on the outside wall and the grill is open, so air does come out. I also put a toilet paper against the grill and it stayed on to the grill, so there is suction.
The fan is about 5 ft. from the center of the shower stall.

Any idea what's going on and how to solve it, other than ripping the ceiling off and put a much stronger (and louder) fan?

Thanks in advance, and pardon the long story.
 
Attached Images  
  #2  
Old 03-01-17, 05:04 PM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
I just made notes as I read, sorry, but I hate long posts, just my short attention span. Here are those notes:
Have you measured the humidity in that space?
Is there a space under the door for air to get into the bathroom?
Could open a window a bit.
What is the cfm capacity of that fan?
Are those showers long and steamy?

Bud
 
  #3  
Old 03-01-17, 05:40 PM
S
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Received 0 Votes on 0 Posts
Have you measured the humidity in that space?
No, not sure how to measure it.

Is there a space under the door for air to get into the bathroom?
Yes

Could open a window a bit.
I can, but we live in NE so I would not want to open a window in the winter

What is the cfm capacity of that fan?
80 cfm and according to my calculations, the room is rated at 40, so the fan should be enough for this room.

Are those showers long and steamy?
Frankly - don't know, but could be, knowing the water temp. that my wife likes to have in her showers.

That being said - it seems like the fan cannot draw any humid air at all, that's my impression anyways.
 
  #4  
Old 03-01-17, 06:31 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
You can buy a half-way decent humidity indicator (with temperature) at Wally World for less than $10.

Bud has hit the major points, the "crack" under the door does need to be more than just a crack, a gap of at least an inch clear space is minimum. Have her try showering with the door actually open a bit.

Are you certain she has the fan running while actually showering? When I was married my wife refused to turn on the fan until after she got out of the shower, I don't know what her problem was running the fan and shower at the same time. Waiting until the room air is already saturated with moisture is not going to work.

Did you install the fan with the proper sized exhaust duct and actually exhausting to the great outdoors? Using a smaller duct or simply exhausting to the attic doesn't cut it.

The last issue, unlikely except in a modern well sealed house, is that the house simply cannot take in enough outside air via leaks in the construction to allow the full 80 CFM outflow.
 
  #5  
Old 03-02-17, 04:23 AM
S
SBI
SBI is offline
Member
Thread Starter
Join Date: Dec 2004
Location: USA
Posts: 384
Received 0 Votes on 0 Posts
You can buy a half-way decent humidity indicator (with temperature) at Wally World for less than $10.

Bud has hit the major points, the "crack" under the door does need to be more than just a crack, a gap of at least an inch clear space is minimum. Have her try showering with the door actually open a bit.

Are you certain she has the fan running while actually showering? When I was married my wife refused to turn on the fan until after she got out of the shower, I don't know what her problem was running the fan and shower at the same time. Waiting until the room air is already saturated with moisture is not going to work.

Did you install the fan with the proper sized exhaust duct and actually exhausting to the great outdoors? Using a smaller duct or simply exhausting to the attic doesn't cut it.

The last issue, unlikely except in a modern well sealed house, is that the house simply cannot take in enough outside air via leaks in the construction to allow the full 80 CFM outflow.
She doesn't have a choice whether to turn it on or not, it has a motion sensor (in addition to humidity sensor) and turns on automatically whenever someone enters the bathroom and stays on for as long as I set the timer (can be set from 30 seconds after the person leaves up to 30 minutes). The fan has constant power and is controlled by the motion/humidity switch or by an options wall switch.
The ducting is correct and it is venting to the outside, as I mentioned. And yes - the vent in the outside is open when it's on.

Not sure how a humidity sensor would help. Clearly there is a high humidity in the shower, the question is why is the fan not clearing it.
 
  #6  
Old 03-02-17, 04:36 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
I suspect your gap under the bathroom door or whole house air leakage, as Furd stated, is not enough to provide the 80cfm of replacement air your fan needs. A 1" gap under a 30" door provides 30 in² of opening. That's equivalent to a 3" hole which is 25% less than a 4" duct. Being smaller means you need to leave the fan running longer.

With 320 ft³ of volume an 80 cfm fan should replace all of the air every 4 minutes. That's probably not happening.

Check your whole house humidity, if high then the house may be on the tight side. But it is the humidity level inside the house that is replacing that bathroom air (we know the bathroom is at 100%) thus if the house is at 50% it will take much longer to get the bathroom down to below condensation levels.

Bud
 
  #7  
Old 03-02-17, 01:40 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,795
Received 8 Votes on 8 Posts
80 cfm for any bathroom with a shower is small. I size them up the same way you do for commercial applications. 50 CFM per fixture is code. So 1 toilet 1 shower is a minimum of 100cfm. id get 120cfm fan. plus fan needs to run at least 20 minutes after showering.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: