20年的屋顶在一半月renew property Insurance 前， 保险公司要求做Roof Cleaned/or

我们刚收到保险公司的通知，在一个半月后 renew 房屋保险之前，要做 " Insurance company will want either (1) the roof cleaned  or (2) an inspection by a licensed roofing contractor that addresses the discoloration in the inspection report.这房子的roof 有二十年了

（Discoloration is natural, occurs over time, and is usually not indicative of a problem. ）

上来问问这种 Discoloration 的 roof cleaned 如何去做？ 有contractor 能做吗？

有经验的房东给些 建议， 谢谢。