A question about dehumidifiers
 

My master bedroom (with attached master bath) has a serious humidity problem. So much so, there there is a little bit of mold starting to grow on the ceiling in the corner closest to the bathroom. Certainly not a healthy environment to be sleeping in!

So I went out today and got a decent dehumidifier from Sears. It's a Kenmore 50 pint unit with digital humidity level setting, timers, and the auto off / bucket is full feature. In a short two hours, it pulled out 4 cups of water from the air! Definately too much H2O in there!

BTW: The reason for the higher humid levels is pretty easy to explain - two reasons: ONE: we do not have a fan in the bathroom, but that will shortly be resolved (once the electrician gets to our house!). and TWO: for the past year, we've kept the bedroom door closed to the rest of the house. We've got a pet rabbit that roams freely throughout most of the house, and we don't want the bunny in our bedroom chewing up our nice furniture. Yes, we have a free-range rabbit - it's my wife's. But I digress...

I need to know what is the ideal humidity level for a bedroom. My dehumidifier has a range from 35% all the way up to 75% humidity. (Whatever setting I set it to - the unit will automatically shut off when that level is achieved. Or, I can also bypass the levels and run it full blast in manual mode, of course).

I know that I need some humidity in the room - otherwise the furniture and such will get too dry. But I certainly don't want it as humid at it has been. Anyone know what's a good level?

Thanks,
-Zoltan.

Check out my humidifier thread.... Someone posted some info about humidty levels above 40% being condusive to mold... So I'd set it around 35 or so... That's about right for comfort during the dry winter months...

Oh no - we have to be careful here - if your humidifier thread and my dehumidifier thread wind up next to each other, they are liable to cancel out each other! :eek:

-Z

That much moisture seems almost impossible if you heat and cool the bedroom with forced air. Are you sure that there is not some sort of water leak? Use 35% until you get rid of the mold.

Stoney brings up another good point. As long as you have a common heating and cooling source, the furnace is going to bring in more moist air into the bedroom.

More long term way to solve the issue is to look for a de-humidifier that fits on the furnace and do the whole house. Personally if you are seeing mold on the outside inside a room, I really would fear what might be growing behind the walls.

Z, you really do not want mold in ANY house and its time for some strong action if you want to stay in the house. There are horror stories about people whose dream house was torn down (and insurance not paying for it) to be rebuilt over again due to mold. I had some in my house in Dallas and had to fix it prior to its sale.

JA

Is that called a central air conditioner:)

It is hard to believe you have too much humidity in the winter time. Do you have forced air heat? Do you live in a basement?

Rick,

The problem is that few if any people want the air conditioner running in the winter. Its usually somewhat cold out there and no need to make it colder inside. Many houses have a de-humidifier on the furnace that takes the humidity out when the heating portion of the furnace is on.

As Noah says, the humidity is coming from somewhere. Even if your bedroom is shut off, its getting fresh air everytime the furnace comes on (I assume you have forced air and not heated water heat?) so am wondering if you have a leaky pipe behind a wall or somewhere in that area. If so its time to start boring small holes and stick a borescope around and see what you come up with. It may not be good but the longer you wait, the more the mold grows..

JA

Yep, a humidifier is a "band-aid". Get to the root of the problem and get some additional ventilation in there. Can you tie in an exhaust vent in the closet with the bathroom exhaust vent and exhaust it out the roof? We have a Broan MP100, which allows up to four 4" exhaust ducts to connect to a "ramote" fan motor that exhausts it out a 6" exhaust duct. We reduced the 6" exhaust to a 4" and have two bathrooms and two showers using it and it is very effective...

Re: A question about dehumidifiers
 

I think he's identified the cause:

We actually had the same battle last year. Shower & hottub off the master bedroom, with no bathroom fan. Got very little use with the previous owners, but it gets 2 showers a day with us, and we had mildew on ceiling & windows. Problem went away as soon as we put in a bathroom fan.

One suggestion: Where this is off your bedroom, get a top-end fan. We went through 3 before we found one that was quiet enough. Going by advertised "sones" alone is deceiving, some are higher pitched than others. In the end I went to my neighbor's house, asked if I could listen to his bathroom fan, then went out and bought the same one.

I had mold in bathroom with no fan. It can be scary how fast it will grow. Put fan in last winter and have not had mold since. Use a good primer when you paint any surface that has been affected. I also run a dehumidifier in basement year round. Never have visible water but always cold damp feeling before. Now nice and comfy.

Thanks for the responses, guys. Appreciate your concerns.

After running the dehumidifier an additional 3 hours, the total water sucked out of the room was around 1 gallon. To be fair, two showers were taken during this time as well. But this morning, the bedroom windows were dry - in the past they've been covered in mist. And the room feels noticably dryer. So the dehumidifier is doing the trick for now...

To address some points:

- I do not have forced air - it's baseboard heating (aka heated water heat.) But that's supposed to be a dryer heat anyway.

- I do not have central air either (shocking in this modern world!) I do have a window A/C unit that I put in my bedroom every year - this year, we used it exactly ONCE the whole summer. Most of time, we have a small two-fan window fan unit that pulls in fresh air from outside. But obviously that fan isn't strong enough to push all the humid air out.

- The likelyhood of the issue being a leak in the pipes is minimal at best - there are no pipes running in the walls of the bedroom. See diagram. Although the roof is 20+ years old, it doesn't leak. That said, I will poke around the room to see if there's a source of water that I'm not aware of. Fortunately, underneath the room is my garage, so I can have easy access there, and above the room is the attic. (It's a bi-level house, BTW).

- I have a small apartment downstairs on the other side of the house - and I have noticed that it the air is a little stale there if it is closed up for some time.

- The house itself is built half-way up a hill, so there is no standing water that I know of, unless runoff from the hill is settling around the foundation. But there's an easement running through my property uphill from the house that is for water run-off. At it's closest point, that pipe is 30 feet away from the house.

- It has been a wetter year in terms of average annual rainfall in our area - so that may also be a contributting factor.

- Per the diagram, the mold is really growing alot in the area just above the door between the bedroom and the bath. The bathroom has been painted with mold-resistent paint which keeps the mold level significantly down. The walls of the bedroom are painted with semi-gloss paint - and there's no mold there either. But the bedroom ceiling is painted in a flat paint - which is more prone to mold, if I'm not mistaken. The ac unit is in the bedroom window closest to the bath, while the fan we usually run is in the other bedroom window.

- Before we had our lovely pet bunny, the bedroom door would remain open for most of the day, which would help air out the room. I think I may buy a baby gate for the door so it can stay open -- while that may bring up the humidity level in the rest of the house a little - I don't think it will lead to bigger problems, since the air to humidity ratio will be more favorable.

- I am also hoping to get the bathroom fan installed ASAP - will look into getting a higher end/quieter unit.

- I do believe the main issue that is causing the mold buildup is lack of ventilation.

http://forums.pelicanparts.com/uploa...1164899830.jpg

Thanks again for the comments and suggestions. There's always good info here!

-Zoltan.

Now that you have a dehumidifier going, wash that mildew off with bleach & water.

Painting:
-Wash with water & bleach to kill mold
-Wash with TSP to really clean down to paint
-Prime with Zinsser BIN primer, you want the shellac based stuff, not water based

As for your little bunny, a baby gate is a good idea, as you suggested. We keep our bedroom closed off to our dogs in the day, but we like the heat from the wood stove downstairs to go in our room.

Our dogs see baby gates as an amusing challenge, and get through them within an hour or two. We're putting in a split bedroom door.

My company investigates these types of problems on a daily basis (I'm in Mich - similar climate to NJ). I was in a house yesterday with 82% humidity!! That house was on a crawl space - the number 1 cause of moisture/mold problems by far.

One of the problems in the first few weeks of the heating season is residual moisture built up in the building materials. This is particularly true in homes without central air conditioning - all that summer humidity is absorbed into the drywall, carpets, insulation and lumber. It takes several weeks for the building materials to 'dry out'. We always have a rash of moisture/mold investigations during November and December.

Although you will see published data indicating "normal" indoor humidity levels as high as 60%, our experience has been to keep it below 40% .... as far below 40 as it's comfortable for you.

Also, by keeping the door closed in your bedroom, it will generally be cooler than other rooms - particularly if its located over an unheated garage. Cold air holds less moisture and moisture will condense out of the air onto cold surfaces such as the walls. With hot water radiant heating (a good type of heat BTW) you don't have the benefit of air circulation blowing around to dry out this surface condensation and mold will eventually grow. You might want to consider a ceiling fan in the bedroom and run it on low continuously. Air movement is good. And get that bathroom fan installed and vent it directly thru the roof, not into the attic. :cool:

BTW: if you really want to learn about this stuff, here's the country's foremost expert on moisture problems in buildings: Joe Lstiburek.

http://www.buildingscience.com/

Lot's of good stuff for free on his website.

Z-Man,
Get one of these: http://www.broan.com/display/router.asp?ProductID=543 and install it in your attic, bring the exhaust outlet through the roof (like Curt said) and run a vent from each room (bath and bedroom) to the unit. Cut the drywall, screw the vents in, cover with diverters, mount the motor/fan assembly in the attic , wire it up to a switch and exhaust it out of the house...you're all set.

Curt,

You're right, that website is great! I learned alot about vapor barriers/retarders and how to properly build a crawlspace. Good resource for homeowners... Thanks!

Curt - you hit the nail on the head with your descriptions of my room and the humidity problem.

Thanks for the website link - I will look into that as well.

-Z

Z-man. When in California, I stay on my boat. A 43 footer. Had a mold problem when I bought it. Took a year of scrubbing and washing to get it all. Installed A/C for the summer, and a portable dehumidifier (like yours) for the winter. My bucket drains into the forward sink, which gravity drains overboard. I have measured the flow. 2 to 3 gallons a day. Boat is dry, cushions crispy, bed is never clammy, things like that. Never any condensate on the inside of the ports. What a difference!

Vent the bath, set the dehumidifier at 35 and keep an eye on the bucket. Is there a way to drain the bucket to the shower drain? Look in the bucket, there is a spot for a hose fitting.

Z- man,

I had a similar situation in the basement but found that emptying the dehumidifier bucket was a real chore, easily forgotten or postponed and of course. while it is off because the bucket is full, the humidity levels rise.

So I got a condensate pump about $70 and plumbed the bucket to the pump with a piece of garden hose. I think most buckets come with a knockout for this purpose.

I plumbed the condensate pump to the outside with a length of compressor hose and it's now doing a fine job, no human intervention required.

Make sure all you vents go outside NOT into the attic. When I got this house we discoverd mold in the attic from a fan not vented out.

Actually air flow is the key to mildew. I have a fan and a dehumidifier in my basement. Works great constant 35% humidity.

If you pulled a gallon out of the air with the door closed, water is coming from somewhere else. A shower will not put that much water into the air.

Look for the real source of the problem

Unless there are trolls hiding in my walls, there's no way the water is coming from anywhere else, as far as I can tell... FWIW, the window AC unit is still in the window, so the rooms aren't exactly sealed.

Oh, and actually, it was more like 1/2 a gallon to 3/4 of a gallon. But still a lot of H2O.

I'll poke around the house to see if there's something I'm not seeing that may be a source of water.

-Z

Z,

If you are not sure, turn off the master water valve to the house for a day and see if there is any change. If there is, then there is a leak somewhere.

Do it on a weekday when fewer people are home and warn them about it beforehand. You get one flush then thats it until its turned back on.

Agree with James that this amount of water coming out of a machine is far too much for a shower. Possible 50 showers but no way with two people in a bathroom.

JA

Unless it a really long, super-extended shower, and them you'd better be pretty wrinkled and cold...

Yes, I've been drinking. So what.

And the problem is? Its dark somewhere in the world so prosit! :)

Ok - so now I'm getting more puzzled by this issue.

Last night, I bought one of those digital humiity gauges. The relative humidity in my bedroom was around 44%. Not too bad. After two showers, the level went up to around 50% - again, not too shabby. This was with the dehumidifier on. After an hour or so, the level went back down to low 40%'s. Again - pretty good.

At around midnight, I turned off the dehumidifier, and the relative humidity was around 42%. No more water was run that night - in the AM, the relative humidity read 60%! Still not too too bad, but it seems like quite a jump from the night before. What gives? (It came back down to mid-40's relatively quickly by running the dehum. for an hour or so.)

As others have said - there may be humidity coming from elsewhere - time to climb up into my attic and poke around....

And per the newsradio, the relative humitidy outside is around 48% this morning.

Still confused,
-Zoltan.

Just checked the attic above the bedroom -

Found a few water drop marks on the beams. But have they been there all along, and I didn't notice them cause I wasn't looking for them?

Felt the insulation above the area of the ceiling that has mold - the upper layer appears to be slightly damp, but the lower layers feel dry. It could simply be the cold - it's about 50 degrees up there.

I took my little humidity gauge up there, and it read a steady 41% - which is lower than the bedroom when the dehumidifier isn't running.

I will have to go back into the attic when it is raining and see if there is water coming through.

-Zoltan.

No bathroom should be without a good ventilating fan ducted to the OUTSIDE, not to the attic or crawl space. I have seen them ducted to a cold attic and whoopie!! When things warm up, signs of wetness on the ceilings and not just in the bathrooms.

Here in the South West our baths are generally in the center of the house, no windows (skylights), but each has a relatively high volume fan.

Additionally, once you find the problem and correct (either inside humidity or outside infiltration, remember the place that shows the damage can be feet away from the actual cause) and eliminate the mold, paint with a product that contains mildewcide. If it is necessary to replace wallboard, go with the new stuff that ha no paper covering. And seal the inside surface that faces the studs.

Been there. Done that.

RH - is just that, "relative" humidty. It is a measure of how much moisture is in the air relative to the maximum it can hold. Dew Point is a better way to look at how much moisture is around in absolute terms. Dew Point is a meaure of the partial pressure of moisture in the air. How quickly we forget our chemistry!

45 dry bulb (air temp) and 29 Dew point would be 42% RH, H20 PP .08 psi
70 dry bulb (air temp) and 50 Dew point would be 40% RH, H20 pp .178 psi
70 dry bulb (air temp) and 59 Dew point would be 61% RH, H20 pp .251 psi

So 40% RH inside your house at say 70 F is very different that 40% RH if the outside temp is 45 F. It will have more than twice the moisture.

If the temp in the room was constant, and the RH rose from 40% to 60%, there is moisture coming from somewhere, and a lot of it. It means that the amount of moisture in the air rose by 50% in a matter of hours. Keep looking for the source.

How does the water get to your baseboard radiators then? Also, do you have a crawlspace or a place where there is dirt under the house and no vapor barrier or are you on a slab?

fintstone: Underneath the bedroom is a garage. There is no crawlspace under the house - it is on a slab / concrete foundation.

And yes - I checked and didn't find any leak around the baseboard radiators - the pip runs alongside one wall - connecting to the bathroom. I will check that again though.

The temp in the room wasn't a constant - it did warm up by daybreak, probably 10 degrees or so.

And whenever I've turned off the dehumidifier, the humidity level would slowly (over hours) start to rise...

-Z

Yeah, Fint, I was thinking he might have a pipe in slab issue under the bedroom, but generally, NJ doesn't use slab foundations.

Z - How does the water get to the bathroom? Where are those pipes located?

red - per the diagram on page 1 - the pipes are located in the wall between the two bathrooms, not in the wall between the master bedroom and the master bath.

Is there a vent from the garage to the roof or is there a bathroom drain that goes in that direction? I had a leak (and wet spot in the ceiling) once and it came from the other side of the house. ran down a rafter. There was a nail driven through the wall that had hit a drain line so it fluctuated based on which sinks/showers were used.

I also had a shower pan once that leaked and the water seeped across the room under the tile and carpet and was wicked up into a wall by insulation. Strange stuff.

Perhaps an exorcist would help.