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Energy Efficient Windows and Doors

Energy Efficiency Basics

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

Replacing older windows with more energy-efficient units can help reduce your utility bills, but it can also make your home more comfortable. Choosing the right windows and doors can help you regulate how much heat comes into and escapes from your home.

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 federal, state, and local energy provider offers and rebates, visit www.energystar.gov/about/federal_tax_credits, or read the Marvin Manufacturers' Certification Statement.

Terms You Should Know

Across products and manufacturers, these are some common terms used to describe the energy efficiency of windows and doors.

Insulating Glass (IG)

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

Gas Fills

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

Visible Transmittance

Visible transmittance is 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. When you look at the ratings, remember that the higher the number given for visible transmittance, the more light that can come in.

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.

U-Factor

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 know is: The lower the number, the less heat a window lets in.

What does it mean to be an Energy Star-certified window or door?

Though not generally a requirement like local, state, and federal building codes, Energy Star certification is a set of standards established to meet what the U.S. government considers an efficient window or door. 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 but is not a factor when it comes to passing inspections. Contact a local building official or certified building professional for more details.

ENERGY STAR Criteria

*Equivalent Energy Performance

ZoneWindow 
U-FactorWindow SHGCDoor U-FactorDoor SHGCSkylight U-FactorSkylight 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≤ 0.45Any
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
Map displaying zones for the respective Energy Star criteria

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. Marvin offers a wide selection of products that meet these rigorous criteria. Learn more at the EPA Energy Star website.

Glass & Glazing

GlazingDescriptionClimateEnergy Performance
Low E1Features a single layer of metallic coating, which blocks heat loss to the outside while reflecting heat back into the room.NorthernLow U-Factor High Solar Heat Gain
Low E2Features 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-CentralLow U-Factor Medium Solar Heat Gain
Low E3Features 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 North-Central South-Central SouthernLower U-Factor Lower Solar Heat Gain
Low ERSA high performance insulating glass that features an additional Low-E coating on the room-side glass surface.Northern North-Central South-Central SouthernLowest U-Factor

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 has the options you need to meet your energy efficiency goals. Reach out to your local dealer or Marvin representative to find out more. Learn more about most efficient products at the EPA ENERGY STAR website.

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, lifecycle performance, and occupant productivity.

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 for new construction, there are plenty of energy-saving windows to choose from.