Throughout North America builders construct homes with no regard with how the sun beams down on the, causing many homes to overcompensate with excessively large air conditioning units. This means that do to poor thinking by the builder the homeowner has an increased cost of operating their home.
If you live in one of those buildings built with no regard for the environment there are things you can do to save some money:
While we often think of curtains and drapes as “window dressing,” their primary function, like that of conventional roller blinds and louvered blinds, is to prevent glare and provide privacy. They can also save quite a lot of energy during the cooling season. According to LBNL research, when installed over clear (not low-e) glass, these attachments alone can block 20%–60% of solar gain (depending on material and color), reducing or preventing the need for air conditioning. For comparison, the highest-performing low-solar-gain windows on the market have an SHGC of 0.20 or lower. While that means that those windows block 80% of solar gain while still permitting a somewhat darkened view, they don’t provide much privacy, so many people will still use curtains or blinds.
Combining the two is a good bet: the curtains offer privacy, while the low-SHGC windows block the sunlight before it gets into the house, which is much more effective (more on this in the discussion of awnings below). One drawback of using curtains or drapes is that you may end up with dark rooms and need to turn on lights, which can cut into energy savings. Louvered blinds can be adjusted at the top to let some daylight reflect off the ceiling, but this light will bring some heat with it—especially if you have clear glass rather than low-e. Another option may be a solar screen that filters sunlight and prevents solar gain but still permits a view—although curtains may still be needed for nighttime privacy.
There’s a lot of information and tips on how to improve your windows here.