Like with most things in life, planning needs to come before you start your purchase process.
Let's get right into an example…
Say you are interested in purchasing 4 windows. These 4 windows are really drafty and just need to go now. There are a total of 16 windows in your house so after replacing these 4, you'll have 12 windows left to replace.
Here's the question…Do you invest in additional energy options in these four windows?
Without further examination of your situation you really don't know.
Some things to consider in a situation like this would be what room are the windows in? How long do you plan on living in the home and do you plan on replacing the rest of the windows? What's your budget?
If I am in this situation and these windows are located in my living room and kitchen and I will not be in the house for more than 5 years, I'm probably not going to invest in additional energy options. Just having highly energy efficient windows scattered in a few places throughout my house will not do me much good without most of the rest of the windows getting replaced.
I also doubt that I will replace the rest of the windows within 5 years so I don't want to invest additional money when it's very unlikely that I will recoup my cost in the form of energy savings.
Now let's look at it from a slightly different angle.
Let's say that these 4 windows are located in my kids bedrooms. Two windows in each room. My situation has not changed…I'm still moving within 5 years and I will probably not replace any other windows before I move.
Because the windows are located in fairly isolated or closed off rooms and because these are my childrens' rooms then I'm going to go ahead and invest more money simply because my kids are going to stay warmer during the winter. The energy savings is going to minimal at best, but the location and the fact that these windows will be protecting my children shed a whole different light on the situation.
This thought process should extend to any type of home improvement decision (and beyond home improvements as well). By putting just a little thought into your process you can be much more prepared when you begin your purchase process. Also, don't be afraid to ask your salesman questions surrounding your thought processes as well. Tell him or her what you are thinking and why and see what their feedback is. Not only do you get the opportunity to learn and get a potentially different and helpful point of view, but you also get a feel for the person you may be purchasing from.
The bottom line is that a little planning can go a long way.