Illinois Replacement Window Tips
The state of Illinois is considered to have two climates, according to the Energy Star Climate Zone Map. Most of the state is in the Northern Region, but a large part of the state is in the North-Central Region. Depending on where you live in Illinois, you want to purchase windows specific to your climate area.
The Energy Star sticker has more of a meaning than whether the product is energy efficient or not. Yes, an Energy Star mark does mean the product is energy efficient but you also have to look at the NFRC ratings to see if the product is energy efficient for your climate area.
NFRC is an independent rating standard that tests windows in 5 areas, U-Factor, Solar Heat Gain Coefficient, Air Leakage, Visible Transmittance, and Condensation Resistance. There is a recommended U Factor rating for every regional climate zone, so when you’re deciding on windows you want to choose ones with the optimal numbers for maximum energy efficiency.
Energy Star Illinois
Northern Region (Blue)
| U-Factor | SHGC | Air Leakage |
| Windows: U ≤ 0.30 Windows: U = 0.31 Windows: U = 0.32 Skylights: U ≤ 0.55 |
No requirement Windows: SHGC ≥ 0.35 Windows: SHGC ≥ 0.40 |
Windows: AL ≤ 0.30 Skylights: AL ≤ 0.30 |
North Central Region (Yellow)
| U-Factor | SHGC | Air Leakage |
| Windows: U ≤ 0.30 Skylights: U ≤ 0.53 |
Windows: SHGC ≤ 0.40 Skylights: SHGC ≤ 0.35 |
Windows: AL ≤ 0.30 Skylights: AL ≤ 0.30 |
NFRC Rating Lable Example for Illinois
In the example to the right, you will see a NFRC label for a window with ratings suitable for Illinois’ Northern Climate Zone. The window has a U-factor of 0.30, a Solar Heat Gain Coefficient (SHGC) of 0.35, and an Air Leakage of 0.2. If you look at the Northern Region table above, you will see that the label for this window meets all of its requirements.
In the label example on the right below the first, you will see an NFRC rating suitable for the North-Central part of Illinois. The window has a U-factor of 0.27, a Solar Heat Gain Coefficient (SHGC) of 0.40, and an Air Leakage rating of ≤ 0.30. According to the table above, the window has a rating suitable for North-Central climate.
