Over time, windows and doors like everything else will wear out and need to be replaced. While it can be costly to update your windows and doors there is an up side - older windows and doors aren't anywhere near as energy efficient as modern units and for most homeowners increasing energy efficiency is their prime motivator for replacing old doors and windows.
What to Look For in New Windows
When it comes to choosing new windows and doors there are a wide range of choices and a lot of confusing, unfamiliar terminology. Energy efficient windows achieve their efficiencies be using a number of techniques such as manufacturing the windows with double or even triple panes of glass to restrict heat transfer between the inside and the outside. Installing an 'inert' gas such as Argon or Krypton between the glass panes to further increase a windows resistance to heat transfer and adding insulation into the window frame itself to minimize heat transfer through the frames. There is even special terminology to describe how energy efficient a window is - U and R factors
Technically, the U factor is a measurement of a materials ability to conduct heat, while R values are a measurement of how well a material resists heat transfer. Windows with a high R value (resists heat transfer) and a low U factor( material doesn't conduct heat well) provide the most energy efficiency.
Even after you figure out how new windows achieve their efficiencies and begin to understand the terminology, the cost of that energy efficiency often induces a form of 'sticker shock' in purchasers since new high performance windows can cost thousands if not tens of thousands of dollars.
Fortunately you can do something to minimize sticker shock on your new windows when improving the efficiency of your windows, since you have some choices - new construction windows, replacement windows and storm windows.
New Construction and Replacement Windows
Both new construction and replacement windows can be made with wood, fiberglass, vinyl or aluminum frames and glazing utilizing double or even triple panes of glass often with Low E argon (or some other inert gas) between the glass panes to prevent heat transfer. Replacement windows are made to fit into an existing opening in a house's framing while new construction windows are designed to be installed (usually from the outside ) and have a nailing flange that will be covered by siding as part of the construction process.
For many homeowners replacement windows are the better choice, as they can provide all the energy efficiencies of new construction windows while minimizing the cost of replacing by using the existing frames and there is no need to remove and reinstall any siding. Unfortunately, in homes where the window frames themselves are badly deteriorated, new construction windows (and new framing) are the necessary choice. It's just not worth the time and money to install replacement windows into old or rotten window frames because the frame will just continue to deteriorate
The downside to replacement windows is because they fit into an existing opening, they do make the window opening itself slightly smaller. However, based on the cost differential, many homeowners feel this is small price to pay.
In addition to the initial cost savings, many homeowners feel replacement windows are a viable choice for them because in many cases they can install their new replacement windows themselves. Here's how -
First, make sure your existing window frame is solid by driving an ice pick or small screwdriver into the wood.
After ensuring your window frame is sound, determine the window material (vinyl, wood etc) and style (casement, double hung) and color you want for your replacement windows , then carefully measure both the height and width of your existing windows. Measure from window jamb to window jamb (side to side) at the top, middle and bottom as well as from the sill to the top of the window at the left, middle and right side. Use the smallest measurement for both height and width to order your replacement windows. Doing this will ensure your new window will fit into the opening, and you can fill in any gaps with shims and insulation.
Use a stiff putty knife or small pry bar to carefully remove the inside stops on your window. Try not to break them so you can use them again and not have to make new ones, then remove the window sash itself using a reciprocating saw to cut through the nails holding the window in place. Once you have the window out, hammer in any protruding nails, remove any old window caulk and give the window frame a quick sanding.
Start installing your replacement window by first dry fitting it into the opening to be sure it will fit.
Next run a fresh bead of caulk along the outside window stops and the window sill then position the new window in the frame. It's important the replacement window is installed plumb and square so use a level to get it plumb and measure from corner to corner to make sure it is square then hold it in place using shims.
Nail the inside window stops in place and caulk between the stops and the window frame to prevent any drafts.
On the outside apply a bead of caulk around the edge of the window and cover the gap between the bottom of the window and the window frame. Usually replacement windows come with an insert you can use to fill the gap, but a piece of wood will do the same job.