Awnings can help keep your home energy-efficient --- they also have a decorative advantage. However, if they get too dirty, they can quickly become a public eyesore. Your instincts might tell you to rent a power washer to do the job. Don't follow your instincts on this one --- a power washer can actually damage the awning, especially if the aluminum is painted. Instead, buy a solvent made for aluminum at the hardware store and a soft brush to scrub away the gunk. If your awnings are too dirty to clean as thoroughly as you'd like, consider (re)painting them after cleaning.
Fill a large bucket with water and add the recommended amount of solvent (refer to the back or side of the solvent bottle).
Wet one awning with a hose. Next, submerge a brush in the cleaning solution, and then scrub the awning. Rinse thoroughly when finished scrubbing; do not let the cleaner dry onto the awning.
Repeat the cleaning process on each awning.
If you miss any areas or if some are hard to reach from the ground, set a ladder against the building near the awning and scrub the area with a hand held brush, rag or sponge. Rinse well.
While the awnings dry, rinse oxidation and soap residue from concrete or wood. It will leave a residue on the former and stain the latter.