Vinyl Replacement Windows Ratings


Vinyl Replacement Windows Ratings

There are four key categories to look at in terms of vinyl replacement windows ratings that will indicate how energy efficient your new replacements will be. We will go through each one and discuss what numbers you should be looking for.


The U-factor measures how efficient a window is at preventing air leaks between the sash and the frame. Here the lower the number the better. Vinyl windows with a number at or below a U-factor of 0.30 is considered energy efficient. Therefore, homeowners should shoot for a window with a U-factor of 0.30 or lower. This factor is especially important for energy efficiency if you live in a cold and windy climate.

Solar Heat Gain Co-Efficient

The SHGC is a measure of how well the glass keeps out or lets the heat from outside. In cold climates, you want to retain as much heat as possible and therefore want a higher SHGC. In warm climates, you generally want less heat penetration through the windows and therefore want a lower SHGC. For the most part, an experienced contractor or company should be able to steer you in the right SHGC number for your climates and for the direction of the windows in your home.

Air Infiltration

Air infiltration or AI is how much air gets through the window and is a test that any manufacturer worth their salt has performed on their windows prior to its release to the public. AI goes from 0 to 1, with 0 being perfect, no air passes through. Now no window lets in zero air, so a mid range vinyl window may have an AI of 0.12. A high end top of the line vinyl window may get an AI rating of 0.02 - check Okna windows as they have excellent AI ratings.


R-value is a measure of the amount of heat loss the windows prevent. Replacement windows get an R-value of between 1 and 5. The higher the number, the greater the efficiency of the window. By extension, the higher the value the more expensive the window, so you want to look for a window with the highest R-value that fits within your budget. If at all possible you should go for an R-value of at least R-3.

More On Vinyl Replacement Windows Ratings

Ratings & Buying

If you are considering how to buy vinyl windows according to the vinyl replacement windows ratings, focus on matching the best ratings to your priorities: It makes sense to pick out the factors that will really make a difference to you – does your home have a problem with heat gain or loss, do the windows face in a particular direction and get more sun, do local building codes require certain vinyl replacement windows ratings, and above all what can you fit into your budget?

If you want to lower heating and cooling costs, look for higher R-Value and lower U-values. If UV light penetration is a concern look for a lower UV transmittance percentage; And in sunny climate look for the lowest SHGC to reduce your cooling bills. The more efficient a window is the more expensive it will be, so getting the best for you is going to be a matter of balance and compromise.

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