The most common siding on a home is vinyl. It's affordable, and durable, and comes in a wide variety of style's. It does require some maintenance though. This siding is not impervious to airborne dust and dirt. Any dirty siding mars your home's appearance, and will eventually attract mold. You should get into the habit of cleaning your vinyl siding twice a year to maintain its color and aesthetic appeal. With the proper cleaning your siding will last for years. Just by mixing one tbs of liquid dish detergent and one gallon of warm water will clean your siding. You will want to cover your grass and bushes or plants with drop cloths before cleaning.
To begin, spray your siding with your hose to rinse off any debris, insects or grime. Then you can scrub section by section with your mixture, using a handled nylon brush. Always start from the bottom up. Rinse after each section as you go. This will get the scrubbed gunk off. Refill your bucket with clean soapy water as needed. The siding will air dry and be dirt free.