Window condensation and mold: How to nuke it from orbit?
February 25, 2014 11:52 AM   Subscribe

My Portland, OR area condo has condensation inside the windows that causes recurring mold growth. Please help me remedy this. Pic and many details inside.

Just to get it out of the way, here's a picture. After a very long period of neglect, I gave the sill/window/runner a thorough cleaning about a month ago with hot water, Soft Scrub spray, and Mold Armor Spray. Within about two weeks, the mold was returning. It's now as bad as it ever was, with patches of fuzzy mold in pink, grey, and black varieties. I know more frequent cleaning is going to be step one, but I want to know what else I can do to eradicate it.

Current Facts
- That picture was taken at about 10:30 AM this morning. I opened the blinds after getting out of bed at 7am, when the condensation extended about a foot up the window. By the end of the afternoon the it will have evaporated except for about 1cm above the seal at the bottom of the window.
- It's about 50 degrees outside, and about 66 degrees in the room. According to a cheap humidity meter, the condo in general is about 70% humidity, the bedroom is nearly 80%, and within a couple inches of the window it's 90%.
- It's a small bedroom (~120 sq ft) with 7'8" ceilings. It's occupied by two sleeping humans from about 11pm to 7am daily. Mini blinds are lowered while sleeping. The bedroom door is open to the rest of the condo.
- We're on the first floor, above a crawlspace. The condo was build in the late 70's. The windows were installed about 10 years ago and are double-paned, but this doesn't seem to provide all that much insulation. Windows in the kitchen and living room have similar issues, but not as bad. So does the sliding glass door to the back porch.
- The condo is owned by my fiancee's parents, so we're pretty much in charge of upkeep (no landlord to call in to deal with this).

So, all that detail out of the way:
1. What's the best way to clean and kill as much mold as possible? There are two cats in the condo, if it affects what sort of cleaning products could be used. I'd like to know as much about specific products and techniques as possible.
2. Aside from continuous cleaning, what can I do to prevent re-growth?
3. How can I minimize condensation on the windows? I've considered a dehumidifier, but I have a feeling that the humidity of the condo as a whole would need to be reduced drastically to keep this from happening. This is the Portland metro area; how dry would I need to keep the house to prevent condensation in typical cold weather (~40F) conditions?
4. The mold likes to re-grow in the corner of the sill, mostly because that's where water pools. How much should I worry about mold having done permanent damage to the window frame (or, god forbid, wall)? Is there anything I can do about this, or would that require hiring a professional?
5. How much of a health risk is this (or might it be)? The condo doesn't smell moldy, but it's definitely scary looking stuff.

Thanks for any tips.
posted by a box and a stick and a string and a bear to Home & Garden (24 answers total) 5 users marked this as a favorite
Lose the blinds (or keep them open).
posted by plinth at 11:58 AM on February 25, 2014 [2 favorites]

1.) Warm water and bleach.

2.) Is the window frame sealed? If you have the ability to, remove the window frame and add a bead of silicone around the window before replacing it. Moisture may be getting in around the frame and then seeping down to the sill and soaking it.
posted by Suffocating Kitty at 11:59 AM on February 25, 2014

How is the condo heated? That seems really too high for an indoor humidity level.
posted by JoeZydeco at 12:00 PM on February 25, 2014

For prevention (not cleaning / killing):

In Zürich, where I live, apartment dwellers are told to air out their apartments for 15 minutes 2x a day (morning and nighttime) regardless of the weather to avoid mold build up.

This is recommended instead of cracking the windows which results in much greater heat loss.
posted by jazh at 12:10 PM on February 25, 2014

Response by poster: How is the condo heated?

Two electric forced air heaters (sort of like this). There's a stronger one in the main area (an L-shaped kitchen/living room set-up, probably about 400 sq ft) and a weaker one in the bedroom. By the time it's warm enough to eliminate condensation, it's too warm for my comfort level (I like to sleep somewhere between 62 and 65F).

Is the window frame sealed?

I'm really not sure... Will have to look into that. I'll do some googling, but if anyone wants to let me know an easy way to be able to tell, that would be great. For being the son of a housing contractor, I have embarrassingly little knowledge about buildings.

In terms of blinds... I really like sleeping in as dark an environment as possible. If necessary, I could leave them up and use an eye mask, but I have a dawn simulator light set up which I really enjoy.
posted by a box and a stick and a string and a bear at 12:15 PM on February 25, 2014

Mold spores are probably endemic in there. You might want to try really airing/cleaning the place at the same time you clean the windows; this might stretch out the time until recurrence. Also wash all towels, bed linens, rugs, etc. to get it as close to 100% clear as possible (similar to allergy cleaning, but you wouldn't have to do it as often, obviously).

It does seem rather humid. Try to reduce that -- shorter showers, no hanging wet towels, maybe reconsider plants. If all that doesn't do enough, maybe consider a dehumidifier.

Mold can be problematic. Even if you don't have allergies now, you can develop the lifelong inconvenience of a mold allergy in conditions like this (happened to me). You also risk running into toxic mold, and making the whole place more attractive to other living creatures.

Good luck!
posted by amtho at 12:18 PM on February 25, 2014

The window frames look like metal. They are cold like outside air. Room air is warmer, and humid. Simple physics lesson in condensation. Glass might be single pane, or double pane but the sealant has failed. We solved the problem in our Portland area house by replacing the windows. If this expense (!) is not an option for you, perhaps keeping a towel on the sill and changing it every morning would help. The advice above to keep the blinds open might also help to reduce the temperature imbalance and encourage airflow.
posted by Cranberry at 12:22 PM on February 25, 2014

You might try Clorox wipes - available at any grocery store - to manage mold control.
posted by Cranberry at 12:23 PM on February 25, 2014

Several years ago I had window condensation in an Seattle-area apartment as well. I had great results from a cheap ($~50), small (about the size of a Nalgene) dehumidifier from Amazon. The model/brand isn't important, and this was years ago anyhow, but I would empty about a cup of water out of it per day.

I put it right next to the window, and it did produce a noticeable humming noise; not sure how that would work for you in a bedroom.
posted by Dilligas at 12:24 PM on February 25, 2014 [1 favorite]

Yeah so the humidity isn't coming from a leaky radiator or runaway whole-house HVAC humidifier.

But that's still way too moist. And heating the room to evaporate the window condensation is just hiding the problem (and probably extracting more moisture out of whatever is going on). You need to find any other sources of moisture that are getting your room up to those levels. At 40F outside your RH% inside really shouldn't be climbing above 40-45% and even lower if the temperatures drop down below that.
posted by JoeZydeco at 12:25 PM on February 25, 2014 [1 favorite]

Response by poster: The window frames look like metal.

Correct. Metal frame, and definitely double paned windows which seem to have intact seals (there's no condensation between the panes).
posted by a box and a stick and a string and a bear at 12:32 PM on February 25, 2014

I have a bathroom that's fully tiled and so prone to condensation. About 18 months ago I bought a Karcher Window Vac (Power Squeegee in the USA) and it's been a revelation. It sucks away moisture like you wouldn't believe. I'd thoroughly recommend it, just run it over the window, it'll take seconds, and it'll suck away all the moisture from the glass.
posted by essexjan at 12:33 PM on February 25, 2014

Do you have a clothes dryer venting to the indoors or something similar?
posted by fritley at 12:41 PM on February 25, 2014

One tip it to keep the slats tilted up on the interior which is the opposite of how they are in this photo This allows for better airflow.
posted by vespabelle at 12:42 PM on February 25, 2014

Dehumidifiers are magical inventions. Mine cost £150 and is about the size of the kind of luggage some people insist is a carry-on bag, with a two-litre tank. If you don't want to spend the local equivalent of that much money, maybe see if you can rent one for a bit to see how much it helps (I suspect it will help a lot). They use electricity and warm the place up, but if you're using electric heat anyway you're not losing anything there. I wouldn't run mine in the room I was sleeping in, but it helps even if you only run it when you're out of the house (if you're a go-out-to-work household, anyway).

Does your bathroom have external ventilation? If not, keep the door shut at all times and keep the mould in there. How do you dry laundry (or, as mentioned above, towels)? Think about where the moisture is going....

Open windows more often, as jazh describes above. Good luck.
posted by Lebannen at 12:44 PM on February 25, 2014 [1 favorite]

Response by poster: Do you have a clothes dryer venting to the indoors or something similar?

Clothes dryer vents to the outside (and we usually use the common area dryer instead since our washer is broken). The only other vent in the house is an intake vent in the bathroom, and to be honest I have no clue where it goes to. The bathroom gets steamy during showers even with the vent on, but it actually dries pretty fast and thoroughly afterward.
posted by a box and a stick and a string and a bear at 12:48 PM on February 25, 2014

Response by poster: Sorry to threadsit, but I'm seriously considering a dehumidifier now. I know the general wisdom is to have the dehumidifier be closest to the identifiable source of moisture, but would it make sense to get a stronger dehumidifier (something like this) to put in a central location to bring down the humidity of the entire condo during the day?
posted by a box and a stick and a string and a bear at 1:13 PM on February 25, 2014

I think you are right and a dehumidifier is exactly what you need. Modern ones have a humidity level setting, so they'll only run as much as necessary.

Ideally it would be somewhere you can run the output hose downhill to a drain. Other considerations are secondary. Dumping it manually is no fun.
posted by fritley at 1:28 PM on February 25, 2014 [2 favorites]

You could possibly replace your blinds with exterior shutters to get the windows warmer. In the winter, you could also set the thermostat higher when the room isn't occupied and open the windows to cool it down before you go to sleep (that's a pretty energy-intensive way of dealing with condensation, but hey).

Are you sure the bathroom fan has an intake? They're usually exhaust-only.

If mold has been recurrent, there is a risk that something is seriously wrong with your house. Since it's pretty common to have these kind of problems in the Pacific Northwest, there are probably people who specialize in dealing with them; I would try to find one of them to make sure the problem isn't deeper.
posted by Monday, stony Monday at 1:59 PM on February 25, 2014

Older metal framed windows like that were likely manufactured with no thermal break in the frame. Modern metal windows have a plastic/synthetic insert between the outside half of the frame and the inside half to avoid condensation just like this. In other words, the condensation is probably a built-in situation; even if the glass is effective, the frame isn't.

I'd lean toward a dehumidifier being the best response.
posted by Benny Andajetz at 2:10 PM on February 25, 2014 [1 favorite]

If you can locate the dehumidifier where it can drain into a drain, instead of having to empty it, you will be happier, even if it is less efficient. Or at least close to where you can empty it.
posted by theora55 at 10:56 PM on February 25, 2014

I used to live in one of the wettest, darkest, most mold-prone PacNW apartments ever, and the only way we could keep mold out was opening up the windows & doors sometimes, even when it was cold. Opening all the windows and doors a couple of times a day will probably go a long way and I'd try that before spending a lot of money on a dehumidifier. Just give it a try and watch how quickly your humidity meter reacts to get a sense of how effective that would be. It usually didn't take more than a half an hour with the windows and the sliding door open to dry things out considerably.

Also, get into the habit of keeping an eye on your humidity meter. Even in our wettest, dankest apartment, we tried to keep the humidity under about 55% in particularly wet weather, and under about 45% in normal conditions. At a relative humidity of 70%, you probably already have mold problems in other parts of the apartment - that's really an alarmingly high number. A dehumidifier will help, but in my experience, vigilance and opening doors & windows to regulate your apartment's internal conditions when things get soggy will go a lot further.
posted by dialetheia at 1:10 AM on February 26, 2014

I should add that this works even when it's wet and raining outside, except on those weird super-warm rainy days. The air outside is generally colder than the air in your house, which means that outside air will hold a lot less moisture and will still be drier than the wet, warm air inside your house.
posted by dialetheia at 1:18 AM on February 26, 2014 [1 favorite]

You need a dehumidifier, stat. Our situation was almost exactly the same as yours:

- Portland-area
- 1970s-era building
- first floor (partially below ground)
- 100+/- sq ft bedroom
- same windows (that could be a picture of our windows, minus the mold)
- mold in the corners of the (very deep) window sill

What helped take care of the problem was a big old dehumidifier. We own the previous model of the 70 pint Frigidaire unit that you linked. It is a godsend.

The first winter we lived here, we noticed condensation on the windows and mold around the corners of the window sills. After cleaning the affected areas with bleach, the next thing we did was buy the dehumidifier. For us, it is a must-have (and must-use!) in winter.

This is honestly the best solution for you right at this minute. It will take care of the humidity problem and help keep the mold at bay while you investigate and see if there are other reasons for the mold. You have so much condensation on your window in that picture and you have to knock that down or the mold will never stop growing no matter how many times you clean it.

When there's visible condensation, I run it in the bedroom with the door closed to quickly lower the humidity, then once the condensation is gone I put the unit in a general area to keep working on lowering overall humidity. (Do that during the day, since dehumidifiers tend to be loud, then move it out of the room later in the day or at night.) Definitely leave it running as much as necessary, especially for the first few weeks so that you can get a handle on the humidity and mold. There are times when it was necessary to just leave it on 24/7.

Let me also say that it's not a huge problem to empty the built-in water bucket, despite what others have said. The bucket doesn't actually hold 70 pints of water (that's just the daily processing capacity), the max capacity on mine is something like 2-3 gallons. Plus, it has a flip-up handle for easy carrying. Just wheel your unit near the bathroom (shorter distance to carry) and dump it in the tub.

Another thing you can do: two summers ago, I bought a gallon of mold-resistant white paint and used it to repaint the entire window sill (including the sides and top). That's also helped quite a bit. If you can't find the paint itself, Home Depot also sells mold-inhibiting paint additive.

If you want to kvetch about how annoying this is, or you'd like some more advice, feel free to MeMail me.
posted by i feel possessed at 10:29 PM on February 26, 2014

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