找一个洋人公司清洗屋顶。平时太忙,就让他们来洗了。周一洗完后今天我一看还是一片绿色的霉点,和没洗一样。
写信去问,他们回信说就:
The treatment that is applied to your roof stays active onsurfaces for up to three years. This treatment kills all moss, algae and lichengrowths that will cause damage to your roof surface and prevent any moss orlichen from growing. This is not an instant clean, the roof can takeanywhere from 6-12 months to come fully clean, but we do guarantee that it willcome clean.”