The grey-green film down the side of your house is not dirt, and hosing it will not shift it. It is algae, it is alive, and it is feeding on moisture from humidity and rain. South Jersey supplies plenty of both.
Soft washing runs at garden-hose pressure. The work is done by a cleaning solution that kills the growth rather than by force, and that is the whole point: blasting knocks the green off the surface, but the roots stay and it comes back within the season. Kill it and the house stays clean far longer.
It also means the wall itself is left alone. High pressure on siding can damage vinyl and aluminum over time, beating up the vinyl and sometimes cracking it, and removing the paint from an aluminum surface. Soft washing treats the algae and the dirt without harming the surface underneath.
Vinyl and insulated vinyl, cedar shake and clapboard, stucco and dryvit, brick, fiber cement and older aluminum siding. Each takes a different mix and a different dwell time, which is most of what twenty years teaches you.
Shaded elevations are always the worst. On most houses the north wall and anything under a tree line will be a shade darker than the rest, and those are the walls that make the difference when the job is done.
House washing is priced on the footprint of the building and the number of stories, with the siding material adjusting the rate. You can measure your own house off the satellite view in the estimator and see the price on screen, no visit or sales call necessary.
Prices are on screen in the estimator, and nothing is due until the work is finished. Book the date yourself when you are ready.