While Mitten vinyl siding is close to being totally maintenance free, it will become dirty just as a freshly painted house, new automobile or any other product which is exposed to atmospheric conditions. Generally, your Mitten vinyl siding can be cleaned satisfactorily through the use of an ordinary garden hose. If this does not do the job then we suggest the following: 
1. Equip a garden hose with a soft bristled, long handle car brush. Avoid using stiff bristle brushes or abrasive cleaners, which may change the glass or the cleaned area and cause the siding to look splotchy. 
2. Where soil is a stubborn nature, (as frequently found in industrial areas) the following cleaning solutions work well. 1/2 cup detergent (Tide as an example) + 2/3 cup trisoduim phosphate (Soilax as example) + 1 gallon of water.
In certain geographic areas where mildew may be a problem, substitute hydro chloride (Clorox for example)  for one quarter water in the above formula
Where the house is extremely dirty, it is recommended that you start from the bottom and go to the top rinsing frequently. Cleaning solutions should be permitted to stand on the surface of the siding for several minutes before rinsing.