Since few window coverings meet all these requirements, a combination of treatments may be the answer. That's one reason why mini-blinds have become so popular. They meet almost all of the considerations above, and can be used alone or in conjunction with other window coverings. The only drawback is their inability to insulate. They lack insulating value and are not airtight.
Blinds are more effective in the summer, because they can block direct sunlight.
Even in summer, however, the insulating effect may be negligible. Blinds reflect some heat if they are light in color, however. If you want blinds in a dark color, you can get some insulating value with duotone blinds, which have a reflective color on the back. There are 3 basic materials mini-blinds are made of. This is the least expensive variety, and very popular, too.