Windows promote heat build-up in your home by two means: the general transfer of heat by contact with hot air on one side of the window and through solar gain from the sun shining directly on the window. Well sealed double-paned windows can defend from the former, but do nothing to slow or prevent solar gain. For that, you must block or reduce sunlight.
Block sun from hitting the window
You can block the sun from outside your windows by any number of attractive and interesting means, from installing retractable awnings to using roll-up outdoor shades. Outdoor roll-ups are available in every material from natural woods like bamboo to engineered materials like vinyl shade cloth. They are hung outside the house to shade windows or patios and are rolled up and down to whatever height is needed. Awnings may be either retractable or nonretractable. While there are numerous high-dollar versions of these, most are relatively affordable and can be installed by the homeowner. A basic bamboo shade with string roll-up control can be obtained by a picky shopper for as little as $20. A stationary awning for a 3-foot-wide window might run as little as $50. Prices on both increase from there with upgraded materials and engineered functions like mechanical controls.
Block sun on the window
Window films , which screen or block strong light, are applied directly to the surface of the window. Window films come in a staggering variety and may be as simple as a gray or silver screening film to a colorful imitation stained glass. They use either adhesive or static cling to stick to the window. Again, you will pay more for elaborate designs and oversized windows, but $20 will buy enough of a basic UV screening film to cover an average sized window. There is an energy savings tax credit available for some types of window film installations.
Block sun with interior shading
Opaque fabric shades, thick drapes and indoor shutters are just a few of the options available for indoor window treatments. Though superior for reducing heat loss through windows in the winter, interior window treatments are the least effective for preventing heat build-up because sunlight is still coming though the window before hitting the interior light barrier. Nevertheless, opaque and reflective materials can accomplish a lot. The most affordable forms of these are varying types of blinds that are built from screenlike materials or fabrics and can be obtained for $25 to $35 per window. Check out opaque roller blinds, which are readily available. These come in a wide range of decorator colors and fabrics, and are often lined on the window-facing side with bright reflective white. Blinds are a good solution that still allows you, if you so choose, to frame your window with drapes or curtains.