In Bowers v. Farmers Ins. Exch., 99 Wn. App. 41, 991 P.2d 734 (Wash. Ct. App. 2000), the insurance company denied coverage for mold damage when the insured's rental house was damaged after tenants converted the house into a hothouse for growing marijuana. Id. at 735.
As a part of the operation, all heat in the house was diverted to the basement. Id. at 736. As a result of the operation, mold grew throughout the house. Id.
The insurance company refused to compensate the insured for her mold-related damage, contending mold was excluded under the policy. The insured argued that the cause of her damage was not the mold, but the vandalism of her tenants, a covered peril.
The Bowers court held that "here, there can be no reasonable difference of opinion regarding the cause of the insured's loss. It was the tenants' acts, which 'in an unbroken sequence . . . produced the result for which recovery is sought.'" Id. at 738.