Is your hot water heating system creating the black film on your walls thru out your house?

Answer:
Indirectly possibly. It is probably mildew. There may be a leak somewhere that is allowing too much humidity to build up or there may not be enough air exchange with the outside. Also, what heat source are you using. If gas fired, the fumes for the combustion have to be going somewhere. Perhaps it is not vented properly or the combustion chamber has a crack.
First answer by Lazuruslong. Last edit by Lazuruslong. Contributor trust: 844 [recommend contributor recommended]. Question popularity: 1 [recommend question].