Is salt effective as a room dehumidifer?

I moved into a new flat recently. After painting my room and installing new furniture, one of the walls started to become discoloured. Further, mould started growing in two places on the wall. Contacting my landlord, it appears that there is a leak in the roof causing the discolouration and mould growth. However, she also suggested that the room was too humid (I agree).

Recently, I’ve been opening the window whenever possible to allow air to circulate. I’ve also been removing the mould with anti-mould sprays and elbow grease. HOWEVER: I leave for the UK this Friday for three weeks for Christmas. I’m terrified that I’m going to return to a damp room overrun with mould. At the moment, I cannot afford a dehumidifier, therefore I need to find a cheap way of keeping the damp at bay (obviously, the window cannot be left open during that time).

I thought about using pots of salt in my room, as salt soaks up moisture quite well. Has anybody had any luck with this technique? Can anybody suggest another substance that could be used in lieu of salt, and is widely available?

Further, what is the best way to kill off mould? A bleach solution? Or would a salt solution also work well? Not many things can survive being desiccated, and the remaining salt solution may prevent future growth.

Thanks for any help.

I think rice would have a similar effect, but both are probably impractical–over the course of three weeks, it’d have to absorb gallons of water.

Lowering the thermostat may keep the humidity down a bit, but really, this is only treating the symptom.

Perhaps it’s in your landlord’s interest to invest in a dehumidifier, particularly if she knew about the problem before you moved in. Would you be able to run a hose from the dehumidifier to a drain?

Dunno about killing mold–I’d stick with bleach, but I’ll defer to others.

Er, scratch the bit about the thermostat. Still waking up.

Salt doesn’t soak up moisture from the air. The reason that salt draws moisture out of meat (for example) is osmosis: the cell membranes are permeable to water but not to salt, so salt on one side of a membrane will cause water to flow to the salty side to equalize the salinity. No such condition exists when you put a plate full of salt in a room.

There is a product called Damprid that removes moisture from the air. Home Depot sells it. I haven’t used it myself, but I’m sure it would be more effective than salt.

An air conditioner will dehumidify the air. Does your flat have one?

As for controlling the mold: any good paint store should sell fungicides that you can add to paint to control mildew. If you have any left-over paint, you could add some fungicide and paint over the affected areas before you leave for the UK.

It occurs to me that your landlord has an interest in fixing this problem. It is her building that is being affected. Can’t she do something to minimize the problem, at least while you are away?

I beg to differ: Salt does soak up moisture from the air. The solution of salt in water is an exothermic process that happens spontaneously if you leave salt in damp air. I used this myself when I was living in a damp basement apartment as a student, and the salt definitely got very wet if I left it in an open container for just a day or two.

However, while I definitely pulled some water out of the air, I don’t think the effect on humidity in the room was huge (and I guess it wouldn’t even make a difference if you leave the place for 3 weeks). I suppose the products that Jeff suggested will work a little better, although the principle is probably the same as with salt.

Can you just leave the window open a crack?

I think that while bleach will kill the growing mould, it has little or no effect on spores. You need something like benzalkonium chloride (Rodalon in Denmark) which will also get the spores otherwise the mould will just grow back, since the conditions are so favourable. But the only surefire way is to remove the underlying cause - mould is really just a symptom, not the disease.

Where are you located? Edinburgh? Around here, it would be very unusual to have a room be too humid in the winter – a combination of cold outside air and central heating results in (usually), the need to humidify a room. Further, most dehumidifiers require that the room be fairly warm before they work – because they function by condensing moisture out of the air using cold coils, they work most effectively when there’s a significant temperature differential and the room is quite humid.

So…what’s the source of the humidity in the room? Cooking? Showering? Are there vents? Sounds to me like 90% of the blame goes to the leak in the roof, in which case it should be the landlord’s responsibility to fix it.

That said, you can buy bags or boxes of desiccant at the hardware store and these can usually be recharged by putting them in the stove for a few minutes. But it’s really a patch not a solution to the problem.

No, not Edinburgh. I’m in Northern Italy. It’s about 7 degrees Celsius here outside today, so it’s still quite warm, especially inside. Anyway, I’ve at least bought a load of rock salt to try to make a bit of a difference. Supposedly somebody is coming in the next few days to try to fix the leak. We’ll see.

Isn’t this your landlord’s problem rather than yours? Shouldn’t your landlord be fixing the roof leak. Methinks you should be speaking to an Italian lawyer.