Murdering Mold

written by Roger Smith

Mold

Hi friends, I thought I'd offer some advice on avoiding mold in your apartment in the summer.
If it's your first full summer here, and we've got at least another month of heat and humidity ahead of us. If you're not from a hot and very humid climate you might be surprised to get mold growth, especially on leather goods and clothes.
I’ve been here 6 years, and before Japan I worked on home energy efficiency and healthy homes initiatives.
The basics of beating mold are simple-keep humidity down and let some sunlight in. Mold loves darkness and humidity.
How to do that? There are freestanding dehumidifiers you can buy (除湿器 joshitsuki) which can reduce humidity in a room. They use electricity to create a cool surface for room moisture to condense. You'll need to empty the tank out regularly. They also make the room hotter.
“Aircon” (ductless minisplit heat pumps) also dehumidify in the same manner but are much more energy efficient AND you get cooling for your electricity money. They also drain the condensate water outside, so there’s no tank to drain. They dehumidify in cooling mode (冷房), but if it's a small room it might cool down before the humidity is drawn from the air. In that case you might want to switch to dehumidify mode (除湿 or ドライ) which will run longer until humidity drops more. Note that the room may end up cooler in this mode and it will use much more electricity. Shoot for ~26 degrees, <70% humidity (lower is good). It’s cheaper and better to run it for many hours than to quickly cool a room down to a low temperature and turn it off.
Shoe closets are danger zones. For ones with a door consider getting multiple charcoal containers that trap moisture. Pick them up at Komeri, Daiso, or other home goods stores. These only dehumidify a very small enclosed closed area, so don't bother putting them in an open closet or room as they'll fill up with water quickly.
For clothes closets I would recommend keeping the doors open and letting sunlight and air get in if possible.
Don’t leave anything in contact with a tatami floor. You really do need to put your bedding away or get a wood riser to keep mattresses from touching the tatami.
Keep furniture, boxes, etc. a couple inches away from walls.

Take care of excess moisture at the source. Use a wiper from Ikea or other stores after showers to get as much water off the walls and down the drain as you can. From time to time wipe down walls and the tub with baking soda (重蔵- get at the supermarket or amazon), as mold can’t grow in alkaline environments. No need to start with bleach which puts out fumes that aren’t good to breathe.
Final tip- clean the aircon. If you don’t own it, it’s probably the landlord’s responsibility and you can ask them to do it. Regardless, they have mesh filters that get clogged with dust and are easy to clean by yourself. Knock off dust and wash them with lukewarm water and dry thoroughly before reinstalling. If the system smells musty you can remove the filters and then spray the metal fins underneath with an alcohol spray (get at Loft, Hands and other stores ~1200 yen). There are also cleaning foams you can use, but some are unpleasantly scented and I wonder what’s in them.
Dry out the aircon periodically, especially if you are running it continuously. On some models you can enable “内部 クリーン” which automatically switches to heating mode from time to time to dry out the aircon. If it stops cooling and starts making noise that’s why. Personally I do this and turn the aircon off daily (or at a minimum every couple of days) to let the aircon fully dry out. If you don’t have a cleaning mode, just open the windows and switch over to heating for 20 min. or so, and then turn off the AC for a few hours. 
Good luck and if you have questions specific to your situation feel free to message me. I’m getting good at disassembling Mitsubishi, Daikin and Panasonic aircon to clean the blower wheel and internal surfaces if you want to learn ; )
Feel free to share your tips (or horror stories).