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Replacement Window Ratings Explained.

Replacement Window Ratings Explained For Your Lee’s Summit, MO HomeWhat You Need To Know When Choosing Your

Replacement Window Ratings Explained.

Replacement Window Ratings Explained
For Your Lee’s Summit, MO Home

What You Need To Know When
Choosing Your Windows

Are you in the market for new fiberglass windows in Lee’s Summit, MO? Whether you’re looking to replace one window or multiple windows, there are some key things you need to know before making a selection.

It would seem like replacing your windows would be a straightforward or simple task. However, there are some ratings that windows have that you should be aware of.

We here at Midland Exteriors want you to be informed when you make your decisions, so we want to explain window ratings and how to use them to choose your windows.

Window Performance Ratings

All ENERGY STAR-certified windows are rated in five categories. You can find these ratings on the NFRC label, which will be on every ENERGY STAR-certified window.

  • U-Factor
  • Air Leakage (AL)
  • Condensation Resistance
  • Visible Transmittance (VT)
  • Solar Heat Gain Coefficient (SHGC)


The U-factor measures the rate of heat transfer. This will indicate how well the window will insulate.

The normal range you’ll find when looking at the label will be somewhere between 0.25 and 1.25.

The main thing to understand here is that the lower the U-factor, the better. Between .27 and .30 is normally what you’ll find.

Air Leakage

The AL will measure how fast air passes through the joints in the window. The lower the air leakage value rate, the better the window withstands air leaking through its joints.

An AL of 0.3 or below is considered acceptable by most industry standards.

Condensation Resistance

This rating is important to some people. Your condensation resistance rating is based on how well your window will resist the build-up of water.

Using a scale of 0 to 100, the higher the number, the more resistance to water build up.

Somewhere between 30 and 80 is what you want to find here.

Visible Transmittance

Some people don’t like their windows allowing a lot of light through. This is where the visible transmittance (VT) rating comes in.

Measured on a scale of 0 to 1, the VT of a window is based on how much light it allows to pass through it.

Your normal range here is between .20 and .80, with higher values on windows allowing in more light.

Look for numbers closer to 1 when it comes to VT.

Solar Heat Gain Coefficient

Again measured on a scale of 0 to 1, the solar heat gain coefficient (SHGC) basically lets you know how well the window will block heat from the sun.

With SHGC, you’re looking for a lower number, which indicates that the window allows less solar heat to pass through it.

It can be tricky when deciding on a good number for your SHGC. For Lee’s Summit, MO, a rating around 0.4 is ideal.

These are the ratings that ENERGY STAR puts on windows. Now that you know what these ratings mean and what to look for, you will be better equipped when selecting windows for your home.

We at Midland Exteriors offer incredible fiberglass window replacements in Lee’s Summit, MO.

So, if you’re looking into window replacements in the Greater Kansas City metropolitan area, call Midland Exteriors at (855) 735-8255 for a free estimate.

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