Vinyl siding does not keep water from getting behind.
Does vinyl rot.
Wood that gets wet can eventually develop rot mildew mold and or leaks.
If you leave the rot in place it will spread and could eventually affect structural members or attract wood eating pests.
Fungi and dry rot will continue to spread even if moisture is not present.
Some vinyl siding companies will cover up damaged wood and side right over existing wood rot.
They will frame around rotted window sills and brick moldings cover up rotted trim etc.
My house needs to either be painted or sided and i would rather side it but a couple of old timers have told me that since i live in a very humid area that moisture will get trapped between the vinyl siding and the wood siding and cause the house to rot undetectably.
Vinyl siding is not nearly as low maintenance or attractive as it first appears.
Because the vinyl itself is unaffected you may not notice water infiltration or the issues that it causes rot mold and mildew until it s too late.
Make a better choice.
Vinyl siding itself is water resistant just like any plastic product.
If vinyl siding is functioning as designed most surface rain water will run right off it.
While proper installation should guard against moisture becoming trapped beneath the vinyl siding if this does happen it will accelerate rot promote mold and mildew and invite insect infestations.