When you see your energy bills are way up, it is time to find out where it causes the energy loss in your home.
Aging or low energy efficient windows can possibly be the reason, beside other leakage in the house. Windows can be responsible for unnecessary heat loss, high-energy consumption and cold or warm drafts and can be the reason for the condensation. Windows and the area around them are the biggest single area of heat loss in the home. You can do a simple investigation before consult a professional.
Signs that tells you to replace your windows:
- If your windows develop ice or frosty glaze between the panes, it's a sign that the glass needs replaced.
- If the windows start to rot, there's no stopping it. Rot can not only cause damage to the windows themselves, but to the area around it. Wet rot can attract termites, which can destroy a home.
- If you feel a cold draft in the winter or a warm draft during the summer when sitting near your window, it is a clear sign of poor insulation. This problem can significantly increase your energy bill.
- If your window no longer remains open on its own, requiring you to prop it open, it is no longer in good condition.
- If your windows become fogged with condensation there may be a seal failure. Seal failures are usually fixed by replacing either the glazing or the entire window.
Benefits to upgrade windows with energy efficient ones
Not only more efficient windows can certainly help create a home that is easier to heat and cool, it also is a good investment to replace windows. Financially, it reduces your energy bill. Make home more comfort by decrease the energy loss. You are sure spending some money on windows replacement, but overall you will save a lot of money. 
According to Natural Resource Canada, Windows can account for up to 25 percent of total house heat loss. For more information, read PDF from Natural Resource Canada http://oee.nrcan.gc.ca/sites/oee.nrcan.gc.ca/files/files/pdf/residential/personal/IWEE_EN.pdf. Or visit http://oee.nrcan.gc.ca/home