A question about dehumidifiers

[Z-man]

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.

[cstreit]

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...

[Z-man]

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!

-Z

[fintstone]

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.

[Joeaksa]

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

[rick-l]

Originally posted by Joeaksa
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. 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?

[Joeaksa]

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

[azasadny]

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...

[notfarnow]

I think he's identified the cause:

Originally posted by Z-man
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 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.

[wreckersteve]

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.

[Z-man]

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.



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

-Zoltan.

[notfarnow]

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.

[CurtEgerer]

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.

[CurtEgerer]

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.

[azasadny]

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.

[azasadny]

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!

[Z-man]

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

[fingpilot]

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.

[Ned nyna 11]

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.

[targa911S]

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.