How to Interpret and Utilize Window Performance Labels

Ever wonder what all those numbers listed on a window label mean? 在本文中, guest contributor Randy Williams explains how to make use of performance data, particularly thermal performance data, when picking out windows for your project.

Back when I was starting out as a general contractor, I relied on the salesperson at my lumberyard to determine the window performance level needed. After all, a window is a window, right? 事实证明，没有.

There are a lot of window selections that should be made based on the location of the project and specific goals of the home. 例如, 如果你生活在寒冷的气候中, you may want to choose a window with more solar heat gain and a lower 的u值. If you live in a hot climate, less solar gain may be needed.

所有这些信息, 和更多的, will be listed on the certification label that’s placed on the window before it leaves the factory. That label is unique to the window configuration and includes performance information specific to its type (casement, 双悬, picture, 等.), materials, 玻璃涂料, and other features.

I’ll explain how to put that data to good use but first, a little background.

Where does the data on the label come from?

安徒生® 窗户和天井门都是 National Fenestration Rating Council (NFRC) 认证. 这个独立的, non-profit industry organization establishes objective window, 门, and skylight energy performance ratings to help homeowners, 建筑商, 架构师, and others making purchasing decisions.

Windows and 门s that are NFRC 认证 are tested by an independent, third-party testing lab. The information gathered during testing includes the following:

• 的u值
• 太阳热增益系数(SHGC)
• 可见光透过率
• 空气渗透

的u值

的u值 values indicate the rate or speed of energy (heat) loss through the window. Considering this measure helps you understand the insulation value of a window.

You might be familiar with R-Value, which measures heat resistance. With R-Value, the higher the number, the better the insulation properties. With 的u值 values, on the other hand, lower numbers are better.

取决于地点, code may specify maximum window 的u值 values to match the local climate zone. For example, code requirements in a cold climate might range from 0.30 and in a hot climate might range from 0.50.

太阳热增益系数(SHGC)

SHGC measures how much solar heat gain is allowed through a window. This metric has a listed value between 0 and 1 with lower numbers allowing less solar heat gain through.

Much like 的u值, energy codes may specify what is allowed based on climate location. 例如，0.25 may be required in hot climates, 0.在较温和的气候条件下, and there’s not likely to be a requirement for SHGC in cold climates (zones 6, 7, 和8).

可见光透过率

可见光透过率 measures how much visible light enters through a window. It’s listed as a range between 0 and 1. One is the maximum amount of visible light and 0 would be a window that you’d have a hard time seeing through.

通常, more panes of glass and different 玻璃涂料 that help improve window performance will also reduce the amount of daylight moving through the window, which results in a lower visible transmittance number.

空气渗透

空气渗透 measures air leaking through the window assembly itself, not air leaking around the window due to any air sealing deficiencies that might occur during installation. Air that leaks through the different parts and pieces of a window will affect comfort and the operating cost of a home.

数字范围从0开始.1 to 0.3，带0.3 being the maximum air leakage allowed.

标签上还列了什么?

Other information that will be listed on a window label includes: the manufacturer’s name, 窗口模式, 材料, 面板数, 玻璃涂料, and any gas fill used in between the panes.

If a window meets the requirements of any energy certification programs, 例如能源之星®, 这也可能被列入名单. 参观 能源之星网站 for information about certification requirements in your climate zone.

Choosing a window based on how it will perform in your climate will yield better results for your project, and performance metrics will help you make the right window choice.