JC CONTRACTORS

Wood windows offer the best -insulated value. Note: They do require more maintenance

Double- paned windows that have a low-E rating, and that have a vacuum-sealed argon fill are a great way to reduce air leaks

Triple paned windows are more energy efficient, however they transmit lower light visibility

Typically nearly all windows mass manufactured today have the Energy Star Program sticker on them which measures the U-value and Solar Heat Gain Coefficient (SHGC) - the lower these two metrics are the better the window should perform

Double hung windows are very common and some choices are efficient enough.  However in extreme climates, they may not be the best option due to the ability for air to come in between the sliders

Casement windows (crank windows) are good in windy climates but do require more upkeep on hinges and seals

Flashing and caulking properly though very simple in window installation, are very important to prevent air leaks

Here are more tips from Energy.gov!