New England Guide To Home Window Energy Efficiency | Rescom

Window Energy Efficiency

New England Window Efficiency Guide

A Crash-Course On Getting The Most Energy Efficient Windows For Your Home.

Energy efficiency is one of the most important things to consider when replacing the windows on your home. That’s especially true in New England, home to some of the country’s wildest weather. 

The million-dollar question: How do you know if a window is energy efficient? After all, there are a TON of brands on the market. And very, very few windows are actually ENERGY STAR®-certified for our region.

Fortunately, figuring out if a window is energy efficient is easy. All you need to know is on the NFRC label attached to it.

The NFRC Label

Everything you need to know is on the National Fenestration Rating Council (NFRC) label. The NFRC is a nonprofit organization that rates window energy efficiency. You can find the organization’s sticker attached to the glass of a window. Here is an example of an NFRC label:

If you’ve already started researching windows or gotten a quote, you may have seen this sticker. So what, exactly, do all those numbers mean? 

Let’s look…


The most important rating for New England homeowners to consider, U-Factor measures how well the WHOLE window insulates on a scale of 0 to 1. The LOWER the number, the better the window insulates.

To meet ENERGY STAR requirements in New England, windows have to have a U-Factor of 0.32 or lower. Our triple-pane windows carry a U-Factor of 0.21, which is 152% more efficient!

Solar Heat Gain Coefficient (SHGC)

SHGC measures how much solar heat passes through the window glass on a scale of 0 to 1. The LOWER the number, the better the glass blocks solar heat.

Since New England gets hot in the summer, SHGC is an important rating. ENERGY STAR requires windows in our climate to have an SHGC rating of 0.42 or lower. Our windows are nearly twice as good with a 0.23 SHGC (182% more efficient).

Visible Transmittance

Visible Transmittance measures how much light (not heat) passes through the glass on a scale of 0 to 1. The HIGHER the number, the more light will pass through the glass.

There is no official ENERGY STAR standard for Visible Transmittance. That said, you’ll want to go with windows that rate at least 0.30 to ensure sufficient natural light enters your home. Our windows rate a 0.42, which is top-notch for triple pane.

Air Leakage

Air Leakage measures the amount of air that passes through one square foot of window on a scale of 0 to 1. The LOWER the number, the better the draft protection.  

With Air Leakage, you want to look for windows with a bare-minimum rating of 0.30. Our windows have an Air Leakage rating of 0.08, making them 375% more airtight for premium draft-proofing.

ENERGY STAR-Certified Windows

Even though it’s good for a window to have the NFRC label, that doesn’t automatically mean the window is efficient enough for your home. The true indicator of optimal efficiency is ENERGY STAR certification.

ENERGY STAR certification lets you know if a window meets or exceeds energy requirements for a particular area. This certification is attached to the NFRC label and looks like this.

Windows in New England without the ENERGY STAR marker may not meet energy requirements for the region. Many window companies like to advertise that their windows are ENERGY STAR-certified. But what they don’t tell you is that their windows are ENERGY STAR-rated for other parts of the country.

Very few windows are ENERGY STAR-certified for the New England climate… and ours are one of them. Find out more on our ENERGY STAR Windows page.