It is natural for you to want to have the most comfortable temperature in your home, no matter what the season. This means encouraging the heat to stay in the house in winter and keeping it out in summer. The size, amount and position of the windows that you have in your home are an important factor to be considered, because heat and cold can be transmitted via the glass. You should take measures to make sure that your windows are as energy efficient as possible in order to achieve the most comfortable temperature.
Using thick curtains
Perhaps the simplest way to reduce the transmission of heat or cold through the window panes is to use thick curtains. Although the windows themselves will still not necessarily be energy efficient, at least this will affect the comfort level in your home. Curtains will not be able to eliminate the transfer of air through any gaps around your window frames, though, so it may also be necessary to seal the windows.
Double, and triple, glazing
Double glazing make for more energy efficient windows because they have two layers of glass with a vacuum space between the layers. The effect of this is to reduce the amount of heat that can pass through the glass. Double glazed windows keep the heat inside during winter and limit the amount of extra heat that enters the house during hot summers. Windows that are triple glazed (having three layers each separated by a vacuum) are even more effective at reducing the transfer of heat.
Sealing around your windows
If you do have gaps around your window frames or sashes, it will be difficult to keep the temperature in your home constant and comfortable. The resulting temperature drop will cause your heating system to work harder and will push up your bills. You will have to take measures to seal the windows. Unless you live in an old house in which the windows frames have shrunk or shifted over time, or a new house with badly fitting window frames, this should not be a huge task. Caulking your window frames is one of the best options to seal them completely. This involves using a flexible sealant to fill the gaps and to eliminate the passage of heat and cold through the gaps.
Taking measures to make sure that your windows are more energy efficient will help you to be able to maintain a more comfortable temperature in your home. You will also find that the cost of your energy will be reduced.