The thermal envelop of a house plays a crucial role in the effectively of the HVAC fitted inside. Leaky windows of the house are one of the main culprits that facilitate leakage of warm air outside into the surrounding. Many houses are found with defective windows that results in leakages. Having them is like flushing your hard-earned money into toilets. You will often find that old caulking around the window has failed. The glazing of the panes has got damaged. Instead of repairing them it is always a wise initiative to install new windows that are meant to be energy-efficient. These windows are ultimate solution for heating and cooling comfort. Buying energy efficient windows can save you between $126 and $465 a year. It would depend upon the number of windows you replace and where in the United States you live. Here are few things that you should take into consideration while buying an energy-efficient window for the house.

• Buy windows with low-emissivity, or low-E, glass. The coating is capable of blocking almost 90% of sun’s heat that penetrates through window panes. The glass panes have a thick coating of metallic oxide on both or at least on one surface of the glass of the window pane. The advantage of it is that you do not require putting heavy curtains on your windows which make the room dark and deprive you from enjoying the beautiful view outside. There are quite a few options available in insulating-glazing such as - gas fills, tints, reflective coatings, and other styles.

• When you buy energy efficient windows, buy a unit with low U-value. Higher U–value will allow good flow of heat. The U-factor range is usually between 0.20-1.20. So chose from the lower side of the scale, if you are seeking optimum insulation for your residence.

• The design of a window plays an important role in its efficiency. There are various designs available in energy efficient windows. First comes the traditional double-hung windows. In double-hung design the bottom slides up to open the unit. These are quite efficient in preventing heat loss but in extreme climates heat may leak between the sliders.

• These have a crank that swings the window outward to open. They are very useful in windy locations. They can be effective in preventing draft from entering the house and affecting the functioning of your furnace. When wind blows towards the house, they seal themselves tighter. They do require maintenance on hinges and seals. Energy efficient picture windows come in different shapes and sizes. These are also very efficient.

• The materials of the window also determine the level of efficiency. Aluminium widows will not be good choice as they will conduct heat from outside and vice versa. Vinyl window frames are good options, but they expand and contract due to changes in temperature which leave gaps. Fiberglass windows are best but they are expensive.

There are other steps to improve the efficiency of the HVAC. They are