Adding trees, awnings, lattices, or vines to shade exposed areas of your multi-family units' exterior will help reduce your cooling load (the energy required to keep a building cool).
Trees that shade roofs, walls, and even walkways will modify the micro-climate and reduce heat gain. Do a parking usage study to determine if the project is over-parked; the study should be taken at three times during the day, and over a week during three seasons - spring, winter, and summer. If evidence shows more than 10% empty parking spaces, considered approaching the Planning Department for a reduction tree cover, recreation use or on-site retention can be improved by removing paving and cement. In addition, the "heat island" effect can be reduced that way.
What can you do about it?
Use several strategies (like window screens, window film, or landscaping) to shade windows during the summer.
Focus on shading east, west, and south facing walls.
Install window screens.
Coupled with shade from landscaping, window screens can maximize shade potential from your unit. Use screens with a shading coefficient of .76 or lower to reduce heat radiation.
Add awnings and overhangs to windows.
Awnings and overhangs need to be close to the top of windows to effectively shade the glass. A good rule of thumb is to cover half the surgace of glass at the summer solstice (e.g. A 30" overhang at the header will cover the top half of a 4' tall window).
Place trees approriately to optimize solar gain.
Plant evergreen trees on the west and east sides of the building to keep out heat all year long. Use deciduous trees on the south because during the winter, after dropping their leaves, the branches will filter the sun and provide desireable partial passive heating.