Not surprisingly, wood clad and fiberglass window frames rated the highest. (These replacement windows 11 iso also carry the highest price tags.) These window frame materials are better at keeping out the rain, wind and elements. Each window was put through a week of extreme temperatures to see how the window expanded, contracted and flexed with temperature and condition changes. Each window was then tested for water and air leakage. Windows that exhibited little or no change in performance from the start to finish were ranked highest.
Vinyl is less expensive and convenient
Vinyl replacement windows account for nearly 50% of the market because they are reasonably priced and maintenance-free. However, vinyl windows will let some air seep through, especially in colder climates. In addition, vinyl is less attractive than wood clad and is not able to be stained or painted to match or compliment a home’s exterior color.
Replacement Window Ratings
When comparing the same type and style of window from different manufactures or even different lines from the same manufacturer, you have probably noticed one thing: no two windows are exactly the same. Don’t panic! There’s no need to resort to anything as drastic as defenestration – or jumping out of a window. In order to ensure that your replacement windows will provide you with great home comfort and energy cost savings, the National Fenestration Rating Council or NFRC and Energy Star provide a useful rating system for evaluating window quality and energy efficiency.
It can be difficult to compare claims made by different window manufacturers, mainly because they often use different window measures and rating terms to sell their products. For instance, some may use center-of-glass R-value and shading coefficient, while others use whole-window U-factor and solar heat gain coefficient. Fortunately there is now one place to look that has standardized ratings for windows – NFRC. The National Fenestration Rating Council (NFRC) is a nonprofit coalition of manufacturers and window experts that has set standards for testing and labeling windows.
The National Fenestration Replacement Council
The NFRC has developed a fairly comprehensive window performance/ energy star rating where they provide uniform and definitive benchmarks by which all window companies must now measure a window’s energy performance. You can easily compare windows from different manufactures or different lines from the same producer because the information is handily and precisely presented in an easy to understand summary. However, you should be forewarned that windows are evaluated and rated when they are new and therefore long-term resilience is not taken into account. In addition, the Council does not perform studies on already installed windows or their history.
The NFRC Window Replacement Rating System
The key element to the National Fenestration Replacement Council rating system is a window’s U-factor. The NFRC gives each window a U-factor rating. The first number after the words U-factor is the rating that’s appropriate for residential purposes. It will be marked AA or Residential. The U-factor marked BB or Non-Residential is for commercial window applications. The U-factor on the NFRC label always refers to the whole window. To make sure you are comparing apples to apples, ask for the NFRC ratings even when there is no label on your window replacement. Also, be sure to use the same size windows for comparison, because the ratio of glass to framing affects the result.
U-value measures how much heat actually flows through a material. NFRC has U-value measurements of different replacement window systems. Simply put, the lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value. U-factor rating ranges from 0.10 to 1.20. The lower the U-value, the lower your heating costs. You may also want to compare air leakage. This rating corresponds to the ratio between the number of cubic feet of air that passes through a window divided by the square feet of window area. The lower the AL is, the smaller the leakage.
Another factor to consider is Solar Heat Gain Coefficient (SHGC), which measures how well a product blocks heat caused by sunlight. SHGC is the actual measurement of solar radiation (infra red energy or solar heat) that passes through home replacement windows SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits. Whether you want a high or low SHGC number depends on where you live. In the north, where your primary concern is probably heating your home, a high number may work to your advantage. On the other hand, in the south, where the goal much of the time is keeping the heat out, a lower SHGC would be desirable.
Next is Visible Transmittance or VT. VT measures how much light gets through the window glass. This is also a rating between 0 and 1 and like CR the higher the number, the more light gets through. The typical piece of clear annealed glass has a VT of.93, which means 93% of the light that hits the glass passes through. Add a second lite and VT goes down by an additional five percent. The higher the VT, the more light that gets through the window. The lower the UV transmittance the less fading of your drapes and carpet.
