If your doors are old, or just not energy efficient by allowing air to pass through, you should consider replacing them. As always, ask your local contractor for help in choosing the most cost effective option for saving energy, and opt for the Energy Star logo when making decisions on your own.
If you’re considering a sliding glass patio door, or any type of mass-glass door, be aware that it can leak energy even when sealed. For the most energy efficient option when choosing glass, Low Emissivity Glass (“Low E Glass: What Is It, How Does it Work, & Is It Worth It?”), or Low E Glass, is the best choice. Though a little more pricey than regular glass, Low E Glass saves money in the long run by using its extremely thin transparent coating (“What is Low-E Glass & Does it Make Windows Energy Efficient?”) to reflect heat. Low E Glass also reflects hot or cold temperatures back into the home. So, if the heat is on in the house while it’s cold out, the Low E Glass will reflect the hot air (Glass Education Center) back into the home without letting it escape.
Pro Tip: Low E Glass can also be used for windows to save more energy throughout your home. Keep in mind that weather stripping also wears off of windows and doors over time and needs to be replaced as needed.