Replacing your home's windows with new, dual-pane, low-e energy-efficient windows is a wonderful way to save money on your bills and keep your house at a very comfortable temperature. However, if you're on a tight budget, replacing all of the windows can be comparatively expensive. That doesn't mean you're doomed to deal with wasteful single-pane windows forever, though. All you have to do is find the windows most in need of protection, and rank each window or wall from there.
South and West
Typically, windows on the south and west are the ones that need to be replaced because those are the sides of the house that receive the most hot sunlight. Morning sunlight is usually less intense and hot than afternoon sunlight, so windows on the east, for example, would be lower on the list of which to change. If you can only replace a few windows, concentrate on the west and south sides.
The Tree Factor
One thing to look out for is the shade provided by trees. If you have several tall trees on the west side of the house, for example, that block most afternoon sunlight, then changing the windows on the south side becomes more important than changing the windows on the west side. You may want to spend a few afternoons observing how the sun shines through each window; you may find that some of the windows receive more afternoon sunlight than others owing to differences in tree height and branch density. Of course, consistent looks are also important, so if you find some windows on one side that definitely need to be changed, you may want to do whatever you can to get all the windows on that side changed.
Film for the Others
For those windows that you can't afford to change yet, look into having window film added. You might want to avoid placing film on northern windows as those don't usually let a lot of light and heat in, and in fact, what little they do let in can be helpful in winter.
One more strategy is to check with window companies about payment plans and rebates. Many cities and utility companies offer tax breaks, rebates, and grants for replacing older windows with energy-efficient models. These vary and may require an application, so start looking into them now.
You may also want to ask about bulk-buy prices. For example, if you replace a certain number of windows or more, you might get enough of a discount to make the entire package very affordable.
Contact window companies, like Royal Exteriors LLC, to find out what their prices are like and what assistance or programs you might be eligible for. It is possible to get nice, energy-efficient windows even on a tight budget -- you just have to find the right company.