本文发表在 rolia.net 枫下论坛Before you start to do something, you must know the exact cause to the problem. Here is one idea: 1) buy a humidistat(湿度计, available from CanTire or HomeDepot), measure the humidity in the attic. 2) turn on the bathroom vent, take a long and hot shower. 3) measure the humidity again. Then you will get an idea if the humidity of attic is seriously affected by the venting of your bathroom.

If that's the cause, the solution's 关键是要把vent duct到屋顶密闭好。以下工具材料可以在home depot买齐。

• Duct Transition – 一段接到管道末端另一段是一个方形的盒子整个盖住屋顶开口
• Duct Tape – 专用于管道工的胶布
• Aluminum Foil Tape – 铝箔胶布，用于密封管道接口
• Duct Insulation – 用于包裹管道保温，防止因为阁楼温度低而导致湿气在管道内凝结成水倒流(condensation)
• Aviation snip – 铁皮剪

***** 不过我不推荐自己修：一是危险性（不小心可能会弄踏二楼天花板）；二是环境极其恶劣（冷、黑、尘、 空间狭小）。***** Here are some notes I wrote for the job:

... "阁楼里真不是人呆的，又冷又黑，尘灰扑脸（阁楼里天花板上层铺了一层厚厚的松散的隔热纤维，进入阁楼一定要带口罩和保护眼镜，袖口衣领束好）。梁柱横七竖八，高度又矮，经常需要匍匐前进。之前，开玩笑说如果谁不听话就关地下室惩罚，现在找到更恐怖的地方了。再有，阁楼没有地板，只是若干横梁下面就是二楼的天花，万万不能直接踩上去，否则就会踏破天花直接掉回二楼了。于是，把大床的床板（9条木板条）拆下运到阁楼，铺设栈道，用于立足行进。" ... 两个排气管道，分别用了两个周末完成。第一个用了3个多小时，第二个用了4个多小时。...

I didn't ask for a quote on this job. so I have no idea how much it will cost for hiring a contractor to do it.

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