OK, found something abotu my house that disturbs me greatly, now that we’ve moved in.
I have two upstairs bathrooms that are used to take showers at least three times a day, each. Both bathrooms are connected to a good HRV that is being used as whole-house ventilation as well as bathroom venting and moisture removal. I was reassured that the HRV (Imperial brand) was perfectly capable of doing the job.
What happens is, first, third or fifteenth shower of the day, it doesn’t matter, we push the button for the HRV to go in “HIGH” mode and start the shower. In five minutes or less, the bathroom is a cloud of steam and there are visible rivulets of water running down all the walls and on the ceiling (the ceiling in one room is sloped, the other is flat). In ten minutes after the shower is off, the steam is gone and the walls are wet. I can’t imagine the shower actually damaging the bathroom, but the condensation is a bit unnerving. The best HVAC installer in the county put this in and he guaranteed it would work fine. I can’t tell if this is “fine” or not. Due to a bit of short-sightedness on my part, neither bathroom has a window or other source of outside air, although the bathroom with the sloped ceiling is open to the rest of the house (it has partition walls only) and should never have a moisture or odor problem.
I’d like to solve this, ‘cuz it freaks me out. I’d hate to have to do mold remediation and re-paint or drywall this place in three years. The fart fan really oughta draw that air out of the bathrooms faster than it does.
Replies
Do you have any source of makeup air into the bathrooms?
How much is the door under cut?
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Well, believe it or not, the worst one is the bathroom that is open to the house. The bathroom is laid out so that there is a small foyer, for lack of a better word, in which there's a laundry chute. The other side of that room has a wall that only goes up eight feet, but the ceiling's at 12 feet, and there's only one door. So any amount of makeup air is coming into the room - hundreds of CFM if necessary.
The other bathroom has about a 1/2" gap under the door - but the condensation problem doesn't appear to be quite as bad.
Is there adequate airflow into the house overall - in other words is the house so tight that the HRV can't actually vent outside?
Also, is the ceiling so cold (poor insulation) that the moisture can't help but condense. (or ambient air temp really low?)
Overall humidity high in the house? (not likely this time of year unless you've got an immense humidifier or other moisture source.)
Sounds pretty strange. In my house, we don't have a fan in the bathroom. If the door is closed, we get a fair amount of fog on the mirror, & more on the external window. Usually, though, we leave the door open part way & only get a bit of condensation on the window.
Don
The house is tight, but the HRV seems to vent fine. There's a fresh air vent in the stairwell that blows fresh air into the house 24/7. Air temp is around 65 degrees, the floor is radiant heat and the ceiling is very well insulated (10" structural insulated panels). EVERYTHING is wet - the walls, floors, doors, it's like being in a steam room. General humidity in the house is pretty low otherwise. I agree, it's pretty strange. In my old house, I could take a half-hour hot shower and barely have condensation on the mirror, and that was with a standard Home-Cheapo 100 cfm fan blowing out.
If the ventilator is working like you've said (by drawing a sheet of paper to it) , I think another option to stop condensation is to warm the surfaces of the room with something like a heat fanfor a few minutes before showering. Doesn't take long to warm a room enough to prevent condensation. Rich
It may sound obvious, but is there any kinks or tight bends in the fan exhaust pipe?. If you can't see the pipe, maybe try and see how much air it pulls by putting some smoke by it and turn it on...(incense or cig...) Is the exit open? Sometimes they have a backflow preventer that will not operate smoothly. I also have seen a fantech fan once that the installer had put in backwards, needless to say, it was pretty obvious and luckily a easy fix. It was in the attic.
Obviously it is not pulling well enough for the bathrooms
Da'vue
Yeah we checked it - seems to be pulling fine. It will grab and hold a piece of paper against the grill from a few inches away.
Get some smoke pencils and check the air flow in the room when the HRV is on high.I wonder if the air is bypassing the general area and just flow directly between the source(s) and the HRV inlet..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
But why would it do the same thing in both bathrooms? The 'normal' bathroom, the one with a door gap and a flat ceiling, has the HRV inlet at the other end of the room, on the ceiling. It still is a problem.
JonE
I agree with Bill Hartmann. The first thing I thought of was the the gap under the door. The strongest ventilation system in the world won't move drop air if it can't draw fresh air to replace it.
Dave
Just a step further Jon ... See if you can get a hold of an amp probe to measure the fan motor amperage. Compare the reading to the FLA (full load amperage) on the motor. If the amperage is way below the name plate the fan isn't moving any air. A dead headed fan can still generate enough static pressure to hold that sheet of paper.
Relate this to putting your hand over the hose of your vacuum cleaner. The pressure holds your hand tight and the vacuum's motor speeds up. The motor's amperage falls way off because your hand cut off the air, or workload, of the fan.
Depending on the type of fan, the gap between the fan wheel and the inlet scroll may be too large.
Best of luck