IG Units
The best vinyl window replacements are built using an insulated glass unit, or IG. Insulated glass units are two to three individual glass panes that are bonded to a spacer bar by sealant. It is a great idea to always ask about the insulated glass unit so you can locate the one that will be high quality and have the best performance.
Low-E
Another important element to consider when searching from the best vinyl replacement windows is to look for ones that are low-emittance, or Low-E. These are layers that are thin, usually made of metal or metallic oxide, and are primarily used to reduce the U-factor by limiting the amount of heat flow occurring in the glazed window. In order to block an exorbitant amount of radiant heat transfer, the inner glass surface should be coated with a low-emittance material. While remaining transparent to visible light, many different forms of Low-E coatings are on the market. The variations allow for low solar gain, moderate solar gain, and high solar gain. In vinyl windows, Low-E is generally recommended for only sides of the home where the sun is likely to shine more. The best vinyl replacement windows often have a tint to them.
Low Conductive Gas Filled Units
Using krypton or argon gas between the panes of glass has been reported to make a significant improvement when it comes to insulation. The best vinyl replacement windows will have space that is consumed with dry nitrogen or air before the window panes are sealed together. To reduce the total amount of heat transferred between the inside and outside of the windows, it is recommended to fill the space with gas that is less conductive. Argon is ideal for this endeavor, as it is nontoxic, inexpensive, odorless, clear, and non-reactive. About 1.5 to 1 inch is the ideal amount of spacing an argon-filled unit should use.
Although the thermal performance of krypton is generally better, the production costs are much higher. When the space needs to be thinner than normal between the gazing, krypton is the perfect choice. Using units filled with conductive gas is associated with numerous insulating benefits, but the cost is higher.
What is U-Factor?
The best vinyl replacement windows have a low rate of heat loss, which is indicative of the U-factor, indicating how a window was assembled. When a window has a lower U-Value, the window is better at insulating and will resist heat flow much more efficiently.
What is the SHGC Factor?
Solar Heat Gain is the percentage of the total amount of heat gained from solar energy that penetrates glass. The percentage is calculated based on the amount of heat gained from a combination of absorbed heat and direct sunlight. A small number indicates that the unit is more capable of reducing solar heat gain. The lower values also help to reduce your air conditioning bill in the summer since less heat is absorbed. Depending on the glazing options, the best vinyl replacement windows will have ratings ranging between 0.91 to 0.39. A SHGC of 0.98 is average for the typical single paned wood framed window.
Visible Light Transmission (VT)
VT, or visible transmittance, is a key indicator in determining how much visible light is transmitted. This rating is for the entire window, including the frame. The best vinyl replacement windows will have a high VT, which is ideal during daylight hours. Most values are usually between 0.3 and 0.8.
The previously mentioned terms are all very important to become educated on before you make your purchase. Not only is purchasing a high quality window vital to how the windows will perform, but the installation is equally as important. Poor installation can be responsible for your windows performing poorly, even if they are high quality windows. The best vinyl replacement windows will be taken care of to provide you with an excellent performance that will last for years to come!

What Makes Vinyl Windows So Different?
These windows are made of Poly Vinyl Chloride which is a synthetic plastic made by a chemical process. They are strong and made up of extremely malleable and ductile materials. Thus the special features of  vinyl replacement windows are that they are very light, easy to handle and their cheap prices, when compared to the conventional ones made of wood or metals. Since PVC can also be easily mended, any problem can be effortlessly fixed. Another great advantage is that they are energy efficient and can provide insulation both under hot and cold conditions. No more insane power bills!

Vinyl Windows – The List Doesn’t End Just Yet!
Vinyl windows are extremely easy to maintain and they only require a onetime investment in good quality plastic that can be forged into a robust and aesthetically pleasing window that will last for a long time. The best vinyl windows are made of good quality poly vinyl chloride which is reinforced with other materials to provide extra stability and strength and to retain their colour as well, so that the paint on the windows does not fade away with time as it happens in low quality windows. Also if you choose windows with more chambers, they tend to be stronger and can withstand higher forces of wind. These special types are called vinyl storm windows and are a bit more expensive, but are definitely worth the investment since they can resist even gales. The benefits of these windows can only be truly appreciated when you use them at home!

Installation, Maintenance, Cost?
Another major factor that should be considered is that installing vinyl windows is one of the easiest processes in construction! Believe it! The only tricky part is the removal of the older window, and once that is done, the rest is a walk in the park. There are two ways to go about the installation process; one is the mechanical method, where screws and clamps are used to hold the window in place or, the other method where one can just easily weld the windows into place. Both of these processes can be done by anyone who is good with tools or by a professional. Don’t fret; they usually charges about to three to four times less for vinyl windows than wood or metal ones! Thus everything put together, it should cost only close to 300$ to 400$. Also painting vinyl windows is so simple since the plastic retains the paint very well and we can choose any colour we desire.
All things considered, one of the more attractive features that make people opt for vinyl windows is that they are much cheaper than other windows made of conventional materials like wood or aluminium. This is  because the process of making and synthesizing the material, poly vinyl chloride, is a simpler and cheaper process than the whole process of obtaining the metal or wood, purifying it and casting it into various shapes and sizes.
Different models of vinyl windows are available that have special features but cost a bit more. For example, the vinyl clad windows are normal wooden or metal windows but with a layer of PVC, and vinyl casement windows are windows made especially for casements and it is only the differing quality that raises its cost. Also when you order custom vinyl windows, you can easily personalise them for your own conditions and use for a few more greens. However, in the end you can be rest assured that you are getting great quality, good looks, maximum use and longevity for your windows at dirt cheap prices!