Weather should play a very important role when choosing replacement windows. This is even more so if your area experiences extreme temperatures. For example, you might wish to keep the heat out if you live in a very hot region, but the same heat is welcome in a cold environment. Here are some of the factors to consider when choosing replacement windows for a cold weather environment:
Solar Heat Gain Coefficient
The solar heat gain coefficient (SHGC) represents the fraction of solar radiation that your windows admit. The coefficient is expressed as a number between 0 and 1. The lower the SHGC is, the lower the amount of radiation that a window transmits. How is this relevant in cold climates?
In a cold area, you want your windows to admit the highest amount of radiation possible. This means you should choose a window with a high SHGC (close to1). Such a window will allow some heat to pass through even during the winter.
Another factor to consider is visual transmittance (VT), which is the amount of light passing through the window. VT is also measured as a ratio/number between 0 and 1, and you need to choose a window with a relatively low coefficient. This is because you want your windows to admit radiation (heat); you don't want to deal with the glare.
Of course, this is only applicable for the windows on the walls facing the eastern and western sides of the house. This will enable you to prevent early morning and late afternoon glare. This rating may not matter for non-sunny windows of the house, or you can opt for a high VT if you want natural lighting.
Lastly, you should also consider the U-factor of the windows you wish to install. The U-factor is a measure of the insulative property of your windows, and it is also expressed as a number between 0 and 1. Choose a low U-factor rating so that your windows can trap as much heat as possible within your house. Don't forget that energy efficiency is not just a function of the window glass alone; it also depends on the design and material of the frame. In that regard, you should opt for energy-efficient frames such as vinyl or insulated fiberglass.
These are some of the major consideration, but you might also have some personal preferences such as the aesthetic value of the window designs. These are things you need to discuss with your contractor, such as Beyers Window & Door Inc, before the project commences.