Sunshine Through Trees

Energy efficient Windows & Doors

Energy-efficient windows can help reduce your utility bills and make your home more comfortable.

Marvin offers a variety of window and door options that help you achieve long-term performance and energy cost savings, in any climate.

Energy Efficiency Basics

I need new windows.  What’s the first thing I need to know when it comes to windows and energy efficiency?

Replacing windows with energy-efficient ones can help reduce your utility bills, but the benefits go much further.  Choosing energy-efficient windows makes your home more comfortable, as their performance determines how much heat comes in and escapes out through the windows.


How do I know if a window or a door is energy efficient? 

Certification programs such as those administered by the National Fenestration Rating Council (NFRC) and ENERGY STAR provide ratings designed to indicate a window or door’s efficiency.  Various performance ratings – like U-factor and Solar Heat Gain Coefficient – measure a product’s effectiveness in insulating and blocking heat from the sun, among other things.  See the Glossary of Terms.


Are tax credits still available for energy-saving window and door replacement?

Tax credit programs change often. To stay up-to-date with the latest, visit Here is a link to the Marvin Manufacturers' Certification Statement.


Simply put, U-factor measures how well a window keeps heat inside your home. It’s a measure of total heat flow through a window or door from room air to outside air. Lower numbers indicate greater insulating capabilities. It’s a particularly important measure for climates with colder winters.

Solar-Heat Gain

If U-factor denotes how much heat leaves your home, the Solar Heat Gain Coefficient (SHGC) measures how much radiant heat enters your home. All you really need to remember is: The lower the number, the less heat a window lets in.

Visible Transmittance

The amount of visible light transferred through a window. Low E coatings can reject solar heat gain without significant reduction to visible light passing through the glass.

Energy Star©

Hear builder Matt Risinger explain how the ENERGY STAR program can help you maximize comfort and energy efficiency by selecting windows and doors suited to your climate zone. ENERGY STAR’s U-Factor is a number indicating how well the product insulates, to maintain interior temperatures.

What does it mean to be an ENERGY STAR-certified window or door?

To obtain ENERGY STAR certification, a window or door must meet a set of requirements that are determined by the U.S. government. Those requirements differ based on geography, meaning a window that’s being installed in Minnesota has different requirements than one in Florida. The certification is meant to indicate that the window is energy-efficient in the region where it will be used, and can help homeowners save on energy costs.

Energy Star Criteria

Zone Window U-Factor Window SHGC Door U-Factor Door SHGC Skylight U-Factor Skylight SHGC
Northern ≤ 0.22*
= 0.23
= 0.24
= 0.25
= 0.26
≥ 0.17*
≥ 0.35
≥ 0.35
≥ 0.40
≥ 0.40
≤ 0.26 ≤ 0.40 ≤ 0.45   Any
North Central ≤ 0.25 ≤ 0.40 ≤ 0.26 ≤ 0.40 ≤ 0.50 ≤ 0.25
South Central ≤ 0.28 ≤ 0.23 ≤ 0.28 ≤ 0.23 ≤ 0.50 ≤ 0.25
Southern ≤ 0.32 ≤ 0.23 ≤ 0.28 ≤ 0.23 ≤ 0.50 ≤ 0.25

*Prescriptive Value

Does my window need to be ENERGY STAR certified in order to be energy efficient?

No. While an ENERGY STAR label can be helpful in identifying energy-efficient windows, every home is unique. ENERGY STAR provides a one-size-fits-all guideline but does not take into consideration, for example, the orientation of the house or the number or size of windows and associated Solar Heat Gain. A window expert like your Marvin dealer can help determine which products will work best for you. ENERGY STAR also recognizes products that meet high energy-efficiency guidelines. Marvin offers the industry’s widest selection of wood and clad wood products that meet these rigorous criteria.

Glazing Description Climate Energy Performance
Low E1 Features a single layer of metallic coating, which blocks heat loss to the outside while reflecting heat back into the room. Northern Low U-Factor High solar heat gain
Low E2 Features a double layer of silver on an inside surface of IG glass. It provides year round performance and comfort. This coating option provides better protection against radiant heat transfer than single layer metallic Low E coatings. Northern
North-Central South-Central
Low U-Factor medium solar heat gain
Low E3 Features three layers of metallic silver and provides the lowest solar heat gain performance in climates where sun exposure is intense and cooling costs are high. Northern
Lower U-Factor lower solar heat gain
Low ERS A high performance insulating glass that features a Low-E coating on the room-side glass (4th surface) and low E3 on the 2nd glass surface. Northern
Superior U-Factor lower solar heat gain

Glass & Glazing

Can you help me to better understand the numbers? What’s a good U-factor number? What’s a good SHGC?

Different homeowners seek out different levels of efficiency, but a “good” U-factor is <.30. A “good” Solar Heat Gain rating, meanwhile, on a scale from 0 to 1, is relative to climates in different regions. Low SHGC numbers are best for southern climates where there’s intense sun exposure, whereas higher SHGC values make the most sense for regions with cold winters.

Can you explain Low E coatings?

The ability of a material to radiate energy (heat) is called its emissivity. Extremely thin coatings of special low emissivity (Low E) metallic material are applied to glass panes used in windows and doors to boost their energy efficiency. Low E coatings, usually applied to the inside layers of insulating glass, manage the amount of light and heat either conducted through a window or reflected away from it.

Are triple pane windows the best? The more panes the better, right?

Not always. Triple-pane windows work best when enhanced energy performance is a key objective. Tripane offers a range of low-E configurations for greater Solar Heat Gain control, including panes filled with argon or krypton-argon gas for added efficiency. But no matter how many panes there are, if the window is poorly constructed, poorly installed or allows air leakage, it will not be efficient.

Insulating Glass (IG)

Two or more glass panes separated by energy efficient inert gas or air to reduce thermal transfer.

Low E

Low E stands for low emissivity. Microscopically thin, transparent metal or metallic oxide layers deposited on a glass surface suppress radiative heat flow and reflect interior infrared energy (heat) back to the inside, reducing heat loss through the glass. Various Low E coating options can manipulate heat gain to match different climate needs.

Gas Fills

Argon or krypton mixes slow the movement of warm and cool air in IG airspaces and improve thermal performance.

Tripane Glazing

Energy efficiency is achieved through the use of various window technologies. Low E coatings, frame materials, glazing types, spacers, gas fill, and weatherstripping all contribute to efficient windows. Energy ratings for windows and doors are certified by the National Fenestration Rating Council (NFRC). See NFRC ratings for any Marvin product on the Energy Information Finder Tool page, or by opening the Professional Resources tab on any product page.

Window & Door Glazing Options

Clad Ultimate Casement ¾" IG U-Factor ¾" IG SHGC 1" IG U-Factor 1" IG SHGC
LOW E1 (IG) 0.30
0.30 0.50
LOW E1/ Clr / Low E1 (Tripane) NA NA 0.23 0.39
Low E2 (IG) 0.29 0.29 0.30 0.28
Low E2 / Clr / Low E1 (Tripane) NA NA 0.23 0.26
Low E3 (IG) 0.29 0.19 0.29 0.19
Low E3 / Clr / Low E1 (Tripane) NA NA 0.23 0.18
Next Generation Clad Ultimate Double Hung ⅞" IG U-Factor ⅞" IG SHGC
LOW E1/ Clr / Low E1 (Tripane) 0.25 0.41
Low E2 (IG)
0.30 0.30
Low E2 / Clr / Low E1 (Tripane) 0.25 0.27
Low E3 (IG)
0.29 0.20
Low E3 / Clr / Low E1 (Tripane) 0.25 0.18

High Performance

What else do I need to know if I want to make my home super energy efficient?

It’s easier than ever before. Modern sustainable building methods, like Passive building, LEED® (Leadership in Energy and Environmental Design) and Net Zero building can help you minimize environmental impact and maximize energy efficiency. ENERGY STAR also offers a “Most Efficient” list, a distinction that recognizes products that deliver superior efficiency through cutting-edge technologies and innovations. Marvin is an industry leader in offering a wide selection of products that meet these rigorous criteria.

Is sustainable building the same as high performance building?

Sustainable building refers to both a structure and to processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition. According to the National Institute of Building Sciences, high performance building integrates and optimizes all major high-performing building attributes, including energy efficiency, durability, life-cycle performance, and occupant productivity. Learn more about Most Efficient products at the EPA ENERGY STAR website.

11,279 Certified Window & Door Product/Glass options meet a .20 U-Factor and lower

Can I make my home a high performance building?

There are methods to optimize energy efficiency in a home environment, most easily with new construction. One way is to plan for a building to generate at least as much energy as it consumes. Net Zero homes and Zero Net Ready homes are carefully designed structures that currently or in the future make use of alternative energy solutions such as wind, solar and/or geothermal systems. You don’t need to build a Net Zero home to dramatically improve energy performance in your home. Whether replacing windows in an existing home or designing a new construction, there are plenty of energy-saving windows to choose from.